Simulation of Initiation in Hexanitrostilbene

Science.gov (United States)

Thompson, Aidan; Shan, Tzu-Ray; Yarrington, Cole; Wixom, Ryan

We report on the effect of isolated voids and pairs of nearby voids on hot spot formation, growth and chemical reaction initiation in hexanitrostilbene (HNS) crystals subjected to shock loading. Large-scale, reactive molecular dynamics simulations are performed using the reactive force field (ReaxFF) as implemented in the LAMMPS software. The ReaxFF force field description for HNS has been validated previously by comparing the isothermal equation of state to available diamond anvil cell (DAC) measurements and density function theory (DFT) calculations. Micron-scale molecular dynamics simulations of a supported shockwave propagating in HNS crystal along the [010] orientation are performed (up = 1.25 km/s, Us =4.0 km/s, P = 11GPa.) We compare the effect on hot spot formation and growth rate of isolated cylindrical voids up to 0.1 µm in size with that of two 50nm voids set 100nm apart. Results from the micron-scale atomistic simulations are compared with hydrodynamics simulations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lock- heed Martin Corporation, for the U.S. DOE National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Quantification of discreteness effects in cosmological N-body simulations: Initial conditions

International Nuclear Information System (INIS)

Joyce, M.; Marcos, B.

2007-01-01

The relation between the results of cosmological N-body simulations, and the continuum theoretical models they simulate, is currently not understood in a way which allows a quantification of N dependent effects. In this first of a series of papers on this issue, we consider the quantification of such effects in the initial conditions of such simulations. A general formalism developed in [A. Gabrielli, Phys. Rev. E 70, 066131 (2004).] allows us to write down an exact expression for the power spectrum of the point distributions generated by the standard algorithm for generating such initial conditions. Expanded perturbatively in the amplitude of the input (i.e. theoretical, continuum) power spectrum, we obtain at linear order the input power spectrum, plus two terms which arise from discreteness and contribute at large wave numbers. For cosmological type power spectra, one obtains as expected, the input spectrum for wave numbers k smaller than that characteristic of the discreteness. The comparison of real space correlation properties is more subtle because the discreteness corrections are not as strongly localized in real space. For cosmological type spectra the theoretical mass variance in spheres and two-point correlation function are well approximated above a finite distance. For typical initial amplitudes this distance is a few times the interparticle distance, but it diverges as this amplitude (or, equivalently, the initial redshift of the cosmological simulation) goes to zero, at fixed particle density. We discuss briefly the physical significance of these discreteness terms in the initial conditions, in particular, with respect to the definition of the continuum limit of N-body simulations

ON SOME TERMS DENOTING CREW MEMBERS ON DUBROVNIK SHIPS

Directory of Open Access Journals (Sweden)

Ariana Violić-Koprivec

2015-01-01

Full Text Available The paper discusses selected terms denoting crew members on Dubrovnik ships throughout the history. The titles of the most important crew members are analyzed based on the corpus of the 18th century documents, literary works, and technical literature. The goal is to determine which terms are typical of the Dubrovnik area, whether their meanings have become restricted or extended, and how they have disappeared or remained in use over the centuries. It is obvious that the importance of individual crew members and their positions changed with time. Their responsibilities occasionally overlapped, and certain terms for their positions coexisted as synonyms, either belonging to the standard or local, i.e. colloquial use. A comparative analysis has revealed some specific features of the Dubrovnik maritime terminology referring to the ship’s crew. The terms škrivan, nokjer, nostromo, pilot, gvardijan and dispensjer are lexemes specific for this area. This is confirmed by their use in literary works.

Magnetohydrodynamic simulation of solid-deuterium-initiated Z-pinch experiments

International Nuclear Information System (INIS)

Sheehey, P.T.

1994-02-01

Solid-deuterium-initiated Z-pinch experiments are numerically simulated using a two-dimensional resistive magnetohydrodynamic model, which includes many important experimental details, such as ''cold-start'' initial conditions, thermal conduction, radiative energy loss, actual discharge current vs. time, and grids of sufficient size and resolution to allow realistic development of the plasma. The alternating-direction-implicit numerical technique used meets the substantial demands presented by such a computational task. Simulations of fiber-initiated experiments show that when the fiber becomes fully ionized rapidly developing m=0 instabilities, which originated in the coronal plasma generated from the ablating fiber, drive intense non-uniform heating and rapid expansion of the plasma column. The possibility that inclusion of additional physical effects would improve stability is explored. Finite-Larmor-radius-ordered Hall and diamagnetic pressure terms in the magnetic field evolution equation, corresponding energy equation terms, and separate ion and electron energy equations are included; these do not change the basic results. Model diagnostics, such as shadowgrams and interferograms, generated from simulation results, are in good agreement with experiment. Two alternative experimental approaches are explored: high-current magnetic implosion of hollow cylindrical deuterium shells, and ''plasma-on-wire'' (POW) implosion of low-density plasma onto a central deuterium fiber. By minimizing instability problems, these techniques may allow attainment of higher temperatures and densities than possible with bare fiber-initiated Z-pinches. Conditions for significant D-D or D-T fusion neutron production may be realizable with these implosion-based approaches

Accurate initial conditions in mixed Dark Matter--Baryon simulations

CERN Document Server

Valkenburg, Wessel

2017-06-01

We quantify the error in the results of mixed baryon--dark-matter hydrodynamic simulations, stemming from outdated approximations for the generation of initial conditions. The error at redshift 0 in contemporary large simulations, is of the order of few to ten percent in the power spectra of baryons and dark matter, and their combined total-matter power spectrum. After describing how to properly assign initial displacements and peculiar velocities to multiple species, we review several approximations: (1) {using the total-matter power spectrum to compute displacements and peculiar velocities of both fluids}, (2) scaling the linear redshift-zero power spectrum back to the initial power spectrum using the Newtonian growth factor ignoring homogeneous radiation, (3) using longitudinal-gauge velocities with synchronous-gauge densities, and (4) ignoring the phase-difference in the Fourier modes for the offset baryon grid, relative to the dark-matter grid. Three of these approximations do not take into account that ...

Accuracy of MHD simulations: Effects of simulation initialization in GUMICS-4

Science.gov (United States)

Lakka, Antti; Pulkkinen, Tuija; Dimmock, Andrew; Osmane, Adnane; Palmroth, Minna; Honkonen, Ilja

2016-04-01

We conducted a study aimed at revealing how different global magnetohydrodynamic (MHD) simulation initialization methods affect the dynamics in different parts of the Earth's magnetosphere-ionosphere system. While such magnetosphere-ionosphere coupling codes have been used for more than two decades, their testing still requires significant work to identify the optimal numerical representation of the physical processes. We used the Grand Unified Magnetosphere-Ionosphere Coupling Simulation (GUMICS-4), the only European global MHD simulation being developed by the Finnish Meteorological Institute. GUMICS-4 was put to a test that included two stages: 1) a 10 day Omni data interval was simulated and the results were validated by comparing both the bow shock and the magnetopause spatial positions predicted by the simulation to actual measurements and 2) the validated 10 day simulation run was used as a reference in a comparison of five 3 + 12 hour (3 hour synthetic initialisation + 12 hour actual simulation) simulation runs. The 12 hour input was not only identical in each simulation case but it also represented a subset of the 10 day input thus enabling quantifying the effects of different synthetic initialisations on the magnetosphere-ionosphere system. The used synthetic initialisation data sets were created using stepwise, linear and sinusoidal functions. Switching the used input from the synthetic to real Omni data was immediate. The results show that the magnetosphere forms in each case within an hour after the switch to real data. However, local dissimilarities are found in the magnetospheric dynamics after formation depending on the used initialisation method. This is evident especially in the inner parts of the lobe.

Least squares approach for initial data recovery in dynamic data-driven applications simulations

KAUST Repository

Douglas, C.

2010-12-01

In this paper, we consider the initial data recovery and the solution update based on the local measured data that are acquired during simulations. Each time new data is obtained, the initial condition, which is a representation of the solution at a previous time step, is updated. The update is performed using the least squares approach. The objective function is set up based on both a measurement error as well as a penalization term that depends on the prior knowledge about the solution at previous time steps (or initial data). Various numerical examples are considered, where the penalization term is varied during the simulations. Numerical examples demonstrate that the predictions are more accurate if the initial data are updated during the simulations. © Springer-Verlag 2011.

Multi-Scale Initial Conditions For Cosmological Simulations

Energy Technology Data Exchange (ETDEWEB)

Hahn, Oliver; /KIPAC, Menlo Park; Abel, Tom; /KIPAC, Menlo Park /ZAH, Heidelberg /HITS, Heidelberg

2011-11-04

We discuss a new algorithm to generate multi-scale initial conditions with multiple levels of refinements for cosmological 'zoom-in' simulations. The method uses an adaptive convolution of Gaussian white noise with a real-space transfer function kernel together with an adaptive multi-grid Poisson solver to generate displacements and velocities following first- (1LPT) or second-order Lagrangian perturbation theory (2LPT). The new algorithm achieves rms relative errors of the order of 10{sup -4} for displacements and velocities in the refinement region and thus improves in terms of errors by about two orders of magnitude over previous approaches. In addition, errors are localized at coarse-fine boundaries and do not suffer from Fourier-space-induced interference ringing. An optional hybrid multi-grid and Fast Fourier Transform (FFT) based scheme is introduced which has identical Fourier-space behaviour as traditional approaches. Using a suite of re-simulations of a galaxy cluster halo our real-space-based approach is found to reproduce correlation functions, density profiles, key halo properties and subhalo abundances with per cent level accuracy. Finally, we generalize our approach for two-component baryon and dark-matter simulations and demonstrate that the power spectrum evolution is in excellent agreement with linear perturbation theory. For initial baryon density fields, it is suggested to use the local Lagrangian approximation in order to generate a density field for mesh-based codes that is consistent with the Lagrangian perturbation theory instead of the current practice of using the Eulerian linearly scaled densities.

Atomistic Simulation of Initiation in Hexanitrostilbene

Science.gov (United States)

Shan, Tzu-Ray; Wixom, Ryan; Yarrington, Cole; Thompson, Aidan

2015-06-01

We report on the effect of cylindrical voids on hot spot formation, growth and chemical reaction initiation in hexanitrostilbene (HNS) crystals subjected to shock. Large-scale, reactive molecular dynamics simulations are performed using the reactive force field (ReaxFF) as implemented in the LAMMPS software. The ReaxFF force field description for HNS has been validated previously by comparing the isothermal equation of state to available diamond anvil cell (DAC) measurements and density function theory (DFT) calculations and by comparing the primary dissociation pathway to ab initio calculations. Micron-scale molecular dynamics simulations of a supported shockwave propagating through the HNS crystal along the [010] orientation are performed with an impact velocity (or particle velocity) of 1.25 km/s, resulting in shockwave propagation at 4.0 km/s in the bulk material and a bulk shock pressure of ~ 11GPa. The effect of cylindrical void sizes varying from 0.02 to 0.1 μm on hot spot formation and growth rate has been studied. Interaction between multiple voids in the HNS crystal and its effect on hot spot formation will also be addressed. Results from the micron-scale atomistic simulations are compared with hydrodynamics simulations. 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. DOE National Nuclear Security Administration under Contract DE-AC04-94AL85000.

An alternative phase-space distribution to sample initial conditions for classical dynamics simulations

International Nuclear Information System (INIS)

Garcia-Vela, A.

2002-01-01

A new quantum-type phase-space distribution is proposed in order to sample initial conditions for classical trajectory simulations. The phase-space distribution is obtained as the modulus of a quantum phase-space state of the system, defined as the direct product of the coordinate and momentum representations of the quantum initial state. The distribution is tested by sampling initial conditions which reproduce the initial state of the Ar-HCl cluster prepared by ultraviolet excitation, and by simulating the photodissociation dynamics by classical trajectories. The results are compared with those of a wave packet calculation, and with a classical simulation using an initial phase-space distribution recently suggested. A better agreement is found between the classical and the quantum predictions with the present phase-space distribution, as compared with the previous one. This improvement is attributed to the fact that the phase-space distribution propagated classically in this work resembles more closely the shape of the wave packet propagated quantum mechanically

Numerical computation of the linear stability of the diffusion model for crystal growth simulation

Energy Technology Data Exchange (ETDEWEB)

Yang, C.; Sorensen, D.C. [Rice Univ., Houston, TX (United States); Meiron, D.I.; Wedeman, B. [California Institute of Technology, Pasadena, CA (United States)

1996-12-31

We consider a computational scheme for determining the linear stability of a diffusion model arising from the simulation of crystal growth. The process of a needle crystal solidifying into some undercooled liquid can be described by the dual diffusion equations with appropriate initial and boundary conditions. Here U{sub t} and U{sub a} denote the temperature of the liquid and solid respectively, and {alpha} represents the thermal diffusivity. At the solid-liquid interface, the motion of the interface denoted by r and the temperature field are related by the conservation relation where n is the unit outward pointing normal to the interface. A basic stationary solution to this free boundary problem can be obtained by writing the equations of motion in a moving frame and transforming the problem to parabolic coordinates. This is known as the Ivantsov parabola solution. Linear stability theory applied to this stationary solution gives rise to an eigenvalue problem of the form.

Simulation study of effects of initial particle size distribution on dissolution

International Nuclear Information System (INIS)

Wang, G.; Xu, D.S.; Ma, N.; Zhou, N.; Payton, E.J.; Yang, R.; Mills, M.J.; Wang, Y.

2009-01-01

Dissolution kinetics of γ' particles in binary Ni-Al alloys with different initial particle size distributions (PSD) is studied using a three-dimensional (3D) quantitative phase field model. By linking model inputs directly to thermodynamic and atomic mobility databases, microstructural evolution during dissolution is simulated in real time and length scales. The model is first validated against analytical solution for dissolution of a single γ' particle in 1D and numerical solution in 3D before it is applied to investigate the effects of initial PSD on dissolution kinetics. Four different types of PSD, uniform, normal, log-normal and bimodal, are considered. The simulation results show that the volume fraction of γ' particles decreases exponentially with time, while the temporal evolution of average particle size depends strongly on the initial PSD

Initialization of high resolution surface wind simulations using NWS gridded data

Science.gov (United States)

J. Forthofer; K. Shannon; Bret Butler

2010-01-01

WindNinja is a standalone computer model designed to provide the user with simulations of surface wind flow. It is deterministic and steady state. It is currently being modified to allow the user to initialize the flow calculation using National Digital Forecast Database. It essentially allows the user to downscale the coarse scale simulations from meso-scale models to...

Analysing initial attack on wildland fires using stochastic simulation.

Science.gov (United States)

Jeremy S. Fried; J. Keith Gilless; James. Spero

2006-01-01

Stochastic simulation models of initial attack on wildland fire can be designed to reflect the complexity of the environmental, administrative, and institutional context in which wildland fire protection agencies operate, but such complexity may come at the cost of a considerable investment in data acquisition and management. This cost may be well justified when it...

Initial particle loadings for a nonuniform simulation plasma in a magnetic field

International Nuclear Information System (INIS)

Naitou, Hiroshi; Kamimura, Tetsuo; Tokuda, Sinji.

1978-09-01

Improved methods for initially loading particles in a magnetized simulation plasma with nonuniform density and temperature distributions are proposed. In the usual guiding center loading (GCL), a charge separation coming from finite Larmor radius effects remains due to the difference between the guiding center density and the actual density. The modified guiding center loading (MGCL) presented here eliminates the electric field so generated and can be used for arbitrary density and temperature profiles. Some applications of these methods to actual simulations are given for comparison. The significance of these methods of initial particle loadings is also discussed. (author)

Atomistic simulation of orientation dependence in shock-induced initiation of pentaerythritol tetranitrate.

Science.gov (United States)

Shan, Tzu-Ray; Wixom, Ryan R; Mattsson, Ann E; Thompson, Aidan P

2013-01-24

The dependence of the reaction initiation mechanism of pentaerythritol tetranitrate (PETN) on shock orientation and shock strength is investigated with molecular dynamics simulations using a reactive force field and the multiscale shock technique. In the simulations, a single crystal of PETN is shocked along the [110], [001], and [100] orientations with shock velocities in the range 3-10 km/s. Reactions occur with shock velocities of 6 km/s or stronger, and reactions initiate through the dissociation of nitro and nitrate groups from the PETN molecules. The most sensitive orientation is [110], while [100] is the most insensitive. For the [001] orientation, PETN decomposition via nitro group dissociation is the dominant reaction initiation mechanism, while for the [110] and [100] orientations the decomposition is via mixed nitro and nitrate group dissociation. For shock along the [001] orientation, we find that CO-NO(2) bonds initially acquire more kinetic energy, facilitating nitro dissociation. For the other two orientations, C-ONO(2) bonds acquire more kinetic energy, facilitating nitrate group dissociation.

Perturbations in the initial soil moisture conditions: Impacts on hydrologic simulation in a large river basin

Science.gov (United States)

Niroula, Sundar; Halder, Subhadeep; Ghosh, Subimal

2018-06-01

Real time hydrologic forecasting requires near accurate initial condition of soil moisture; however, continuous monitoring of soil moisture is not operational in many regions, such as, in Ganga basin, extended in Nepal, India and Bangladesh. Here, we examine the impacts of perturbation/error in the initial soil moisture conditions on simulated soil moisture and streamflow in Ganga basin and its propagation, during the summer monsoon season (June to September). This provides information regarding the required minimum duration of model simulation for attaining the model stability. We use the Variable Infiltration Capacity model for hydrological simulations after validation. Multiple hydrologic simulations are performed, each of 21 days, initialized on every 5th day of the monsoon season for deficit, surplus and normal monsoon years. Each of these simulations is performed with the initial soil moisture condition obtained from long term runs along with positive and negative perturbations. The time required for the convergence of initial errors is obtained for all the cases. We find a quick convergence for the year with high rainfall as well as for the wet spells within a season. We further find high spatial variations in the time required for convergence; the region with high precipitation such as Lower Ganga basin attains convergence at a faster rate. Furthermore, deeper soil layers need more time for convergence. Our analysis is the first attempt on understanding the sensitivity of hydrological simulations of Ganga basin on initial soil moisture conditions. The results obtained here may be useful in understanding the spin-up requirements for operational hydrologic forecasts.

Least squares approach for initial data recovery in dynamic data-driven applications simulations

KAUST Repository

Douglas, C.; Efendiev, Y.; Ewing, R.; Ginting, V.; Lazarov, R.; Cole, M.; Jones, G.

2010-01-01

In this paper, we consider the initial data recovery and the solution update based on the local measured data that are acquired during simulations. Each time new data is obtained, the initial condition, which is a representation of the solution at a

Three-dimensional Mesoscale Simulations of Detonation Initiation in Energetic Materials with Density-based Kinetics

Science.gov (United States)

Jackson, Thomas; Jost, A. M.; Zhang, Ju; Sridharan, P.; Amadio, G.

2017-06-01

In this work we present three-dimensional mesoscale simulations of detonation initiation in energetic materials. We solve the reactive Euler equations, with the energy equation augmented by a power deposition term. The reaction rate at the mesoscale is modelled using a density-based kinetics scheme, adapted from standard Ignition and Growth models. The deposition term is based on previous results of simulations of pore collapse at the microscale, modelled at the mesoscale as hot-spots. We carry out three-dimensional mesoscale simulations of random packs of HMX crystals in a binder, and show that the transition between no-detonation and detonation depends on the number density of the hot-spots, the initial radius of the hot-spot, the post-shock pressure of an imposed shock, and the amplitude of the power deposition term. The trends of transition at lower pressure of the imposed shock for larger number density of pore observed in experiments is reproduced. Initial attempts to improve the agreement between the simulation and experiments through calibration of various parameters will also be made.

Numerical simulation of shock initiation of Ni/Al multilayered composites

Energy Technology Data Exchange (ETDEWEB)

Sraj, Ihab; Knio, Omar M., E-mail: omar.knio@duke.edu [Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall, Durham, North Carolina 27708 (United States); Specht, Paul E.; Thadhani, Naresh N. [School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332 (United States); Weihs, Timothy P. [Department of Materials Science and Engineering, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 (United States)

2014-01-14

The initiation of chemical reaction in cold-rolled Ni/Al multilayered composites by shock compression is investigated numerically. A simplified approach is adopted that exploits the disparity between the reaction and shock loading timescales. The impact of shock compression is modeled using CTH simulations that yield pressure, strain, and temperature distributions within the composites due to the shock propagation. The resulting temperature distribution is then used as initial condition to simulate the evolution of the subsequent shock-induced mixing and chemical reaction. To this end, a reduced reaction model is used that expresses the local atomic mixing and heat release rates in terms of an evolution equation for a dimensionless time scale reflecting the age of the mixed layer. The computations are used to assess the effect of bilayer thickness on the reaction, as well as the impact of shock velocity and orientation with respect to the layering. Computed results indicate that initiation and evolution of the reaction are substantially affected by both the shock velocity and the bilayer thickness. In particular, at low impact velocity, Ni/Al multilayered composites with thick bilayers react completely in 100 ms while at high impact velocity and thin bilayers, reaction time was less than 100 μs. Quantitative trends for the dependence of the reaction time on the shock velocity are also determined, for different bilayer thickness and shock orientation.

Migration kinetics of four photo-initiators from paper food packaging to solid food simulants.

Science.gov (United States)

Cai, Huimei; Ji, Shuilin; Zhang, Juzhou; Tao, Gushuai; Peng, Chuanyi; Hou, Ruyan; Zhang, Liang; Sun, Yue; Wan, Xiaochun

2017-09-01

The migration behaviour of four photo-initiators (BP, EHA, MBP and Irgacure 907) was studied by 'printing' onto four different food-packaging materials (Kraft paper, white cardboard, Polyethylene (PE)-coated paper and composite paper) and tracking movement into the food simulant: Tenax-TA (porous polymer 2,6-diphenyl furan resin). The results indicated that the migration of the photo-initiators was related to the molecular weight and log K o/w of each photo-initiator. At different temperatures, the migration rates of the photo-initiators were different in papers with different thicknesses. The amount of each photo-initiator found in the food was closely related to the food matrix. The Weibull model was used to predict the migration load into the food simulants by calculating the parameters τ and β and determining the relationship of the two parameters with temperature and paper thickness. The established Weibull model was then used to predict the migration of each photo-initiator with respect to different foods. A two-parameter Weibull model fitted the actual situation, with some deviation from the actual migration amount.

Influence of changes in initial conditions for the simulation of dynamic systems

Energy Technology Data Exchange (ETDEWEB)

Kotyrba, Martin [Department of Informatics and Computers, University of Ostrava, 30 dubna 22, Ostrava (Czech Republic)

2015-03-10

Chaos theory is a field of study in mathematics, with applications in several disciplines including meteorology, sociology, physics, engineering, economics, biology, and philosophy. Chaos theory studies the behavior of dynamical systems that are highly sensitive to initial conditions—a paradigm popularly referred to as the butterfly effect. Small differences in initial conditions field widely diverging outcomes for such dynamical systems, rendering long-term prediction impossible in general. This happens even though these systems are deterministic, meaning that their future behavior is fully determined by their initial conditions, with no random elements involved. In this paperinfluence of changes in initial conditions will be presented for the simulation of Lorenz system.

Towards Compatible and Interderivable Semantic Specifications for the Scheme Programming Language, Part I: Denotational Semantics, Natural Semantics, and Abstract Machines

DEFF Research Database (Denmark)

Danvy, Olivier

2009-01-01

We derive two big-step abstract machines, a natural semantics, and the valuation function of a denotational semantics based on the small-step abstract machine for Core Scheme presented by Clinger at PLDI'98. Starting from a functional implementation of this small-step abstract machine, (1) we fus...

Out-of-pile test of zirconium cladding simulating reactivity initiated accident

Energy Technology Data Exchange (ETDEWEB)

Kim, J. H.; Lee, M. H.; Choi, B. K.; Bang, J. K.; Jung, Y. H. [KAERI, Taejon (Korea, Republic of)

2004-07-01

Mechanical properties of zirconium cladding such as Zircaloy-4 and advanced cladding were evaluated by ring tension test to simulate Reactivity-Initiated Accident (RIA) as an out-pile test. Cladding was hydrided by means of charging hydrogen up to 1000ppm to simulate high-burnup situation, finally fabricated to circumferential tensile specimen. Ring tension test was carried out from 0.01 to 1/sec to keep pace with actual RIA event. The results showed that mechanical strength of zirconium cladding increased at the value of 7.8% but ductility decreased at the 34% as applied strain rate and absorbed hydrogen increased. Further activities regarding out-of-pile testing plans for simulated high-burnup cladding were discussed in this paper.

Simulating mixed-phase Arctic stratus clouds: sensitivity to ice initiation mechanisms

Directory of Open Access Journals (Sweden)

G. McFarquhar

2009-07-01

Full Text Available The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9–10 October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process

Simulating mixed-phase Arctic stratus clouds: sensitivity to ice initiation mechanisms

Science.gov (United States)

Sednev, I.; Menon, S.; McFarquhar, G.

2009-07-01

The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9-10 October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation

Generation of initial geometries for the simulation of the physical system in the DualPHYsics code

International Nuclear Information System (INIS)

Segura Q, E.

2013-01-01

In the diverse research areas of the Instituto Nacional de Investigaciones Nucleares (ININ) are different activities related to science and technology, one of great interest is the study and treatment of the collection and storage of radioactive waste. Therefore at ININ the draft on the simulation of the pollutants diffusion in the soil through a porous medium (third stage) has this problem inherent aspects, hence a need for such a situation is to generate the initial geometry of the physical system For the realization of the simulation method is implemented smoothed particle hydrodynamics (SPH). This method runs in DualSPHysics code, which has great versatility and ability to simulate phenomena of any physical system where hydrodynamic aspects combine. In order to simulate a physical system DualSPHysics code, you need to preset the initial geometry of the system of interest, then this is included in the input file of the code. The simulation sets the initial geometry through regular geometric bodies positioned at different points in space. This was done through a programming language (Fortran, C + +, Java, etc..). This methodology will provide the basis to simulate more complex geometries future positions and form. (Author)

Suppression of the initial transient in Monte Carlo criticality simulations; Suppression du regime transitoire initial des simulations Monte-Carlo de criticite

Energy Technology Data Exchange (ETDEWEB)

Richet, Y

2006-12-15

Criticality Monte Carlo calculations aim at estimating the effective multiplication factor (k-effective) for a fissile system through iterations simulating neutrons propagation (making a Markov chain). Arbitrary initialization of the neutron population can deeply bias the k-effective estimation, defined as the mean of the k-effective computed at each iteration. A simplified model of this cycle k-effective sequence is built, based on characteristics of industrial criticality Monte Carlo calculations. Statistical tests, inspired by Brownian bridge properties, are designed to discriminate stationarity of the cycle k-effective sequence. The initial detected transient is, then, suppressed in order to improve the estimation of the system k-effective. The different versions of this methodology are detailed and compared, firstly on a plan of numerical tests fitted on criticality Monte Carlo calculations, and, secondly on real criticality calculations. Eventually, the best methodologies observed in these tests are selected and allow to improve industrial Monte Carlo criticality calculations. (author)

Cosmological Simulations with Scale-Free Initial Conditions. I. Adiabatic Hydrodynamics

International Nuclear Information System (INIS)

Owen, J.M.; Weinberg, D.H.; Evrard, A.E.; Hernquist, L.; Katz, N.

1998-01-01

We analyze hierarchical structure formation based on scale-free initial conditions in an Einstein endash de Sitter universe, including a baryonic component with Ω bary = 0.05. We present three independent, smoothed particle hydrodynamics (SPH) simulations, performed at two resolutions (32 3 and 64 3 dark matter and baryonic particles) and with two different SPH codes (TreeSPH and P3MSPH). Each simulation is based on identical initial conditions, which consist of Gaussian-distributed initial density fluctuations that have a power spectrum P(k) ∝ k -1 . The baryonic material is modeled as an ideal gas subject only to shock heating and adiabatic heating and cooling; radiative cooling and photoionization heating are not included. The evolution is expected to be self-similar in time, and under certain restrictions we identify the expected scalings for many properties of the distribution of collapsed objects in all three realizations. The distributions of dark matter masses, baryon masses, and mass- and emission-weighted temperatures scale quite reliably. However, the density estimates in the central regions of these structures are determined by the degree of numerical resolution. As a result, mean gas densities and Bremsstrahlung luminosities obey the expected scalings only when calculated within a limited dynamic range in density contrast. The temperatures and luminosities of the groups show tight correlations with the baryon masses, which we find can be well represented by power laws. The Press-Schechter (PS) approximation predicts the distribution of group dark matter and baryon masses fairly well, though it tends to overestimate the baryon masses. Combining the PS mass distribution with the measured relations for T(M) and L(M) predicts the temperature and luminosity distributions fairly accurately, though there are some discrepancies at high temperatures/luminosities. In general the three simulations agree well for the properties of resolved groups, where a group

The Matter Bispectrum in N-body Simulations with non-Gaussian Initial Conditions

OpenAIRE

Sefusatti, Emiliano; Crocce, Martin; Desjacques, Vincent

2010-01-01

We present measurements of the dark matter bispectrum in N-body simulations with non-Gaussian initial conditions of the local kind for a large variety of triangular configurations and compare them with predictions from Eulerian perturbation theory up to one-loop corrections. We find that the effects of primordial non-Gaussianity at large scales, when compared to perturbation theory, are well described by the initial component of the matter bispectrum, linearly extrapolated at the redshift of ...

3-D simulations to investigate initial condition effects on the growth of Rayleigh-Taylor mixing

Energy Technology Data Exchange (ETDEWEB)

Andrews, Malcolm J [Los Alamos National Laboratory

2008-01-01

The effect of initial conditions on the growth rate of turbulent Rayleigh-Taylor (RT) mixing has been studied using carefully formulated numerical simulations. An integrated large-eddy simulation (ILES) that uses a finite-volume technique was employed to solve the three-dimensional incompressible Euler equations with numerical dissipation. The initial conditions were chosen to test the dependence of the RT growth parameters ({alpha}{sub b}, {alpha}{sub s}) on variations in (a) the spectral bandwidth, (b) the spectral shape, and (c) discrete banded spectra. Our findings support the notion that the overall growth of the RT mixing is strongly dependent on initial conditions. Variation in spectral shapes and bandwidths are found to have a complex effect of the late time development of the RT mixing layer, and raise the question of whether we can design RT transition and turbulence based on our choice of initial conditions. In addition, our results provide a useful database for the initialization and development of closures describing RT transition and turbulence.

An Initial Examination for Verifying Separation Algorithms by Simulation

Science.gov (United States)

White, Allan L.; Neogi, Natasha; Herencia-Zapana, Heber

2012-01-01

An open question in algorithms for aircraft is what can be validated by simulation where the simulation shows that the probability of undesirable events is below some given level at some confidence level. The problem is including enough realism to be convincing while retaining enough efficiency to run the large number of trials needed for high confidence. The paper first proposes a goal based on the number of flights per year in several regions. The paper examines the probabilistic interpretation of this goal and computes the number of trials needed to establish it at an equivalent confidence level. Since any simulation is likely to consider the algorithms for only one type of event and there are several types of events, the paper examines under what conditions this separate consideration is valid. This paper is an initial effort, and as such, it considers separation maneuvers, which are elementary but include numerous aspects of aircraft behavior. The scenario includes decisions under uncertainty since the position of each aircraft is only known to the other by broadcasting where GPS believes each aircraft to be (ADS-B). Each aircraft operates under feedback control with perturbations. It is shown that a scenario three or four orders of magnitude more complex is feasible. The question of what can be validated by simulation remains open, but there is reason to be optimistic.

Agent-based model of angiogenesis simulates capillary sprout initiation in multicellular networks.

Science.gov (United States)

Walpole, J; Chappell, J C; Cluceru, J G; Mac Gabhann, F; Bautch, V L; Peirce, S M

2015-09-01

Many biological processes are controlled by both deterministic and stochastic influences. However, efforts to model these systems often rely on either purely stochastic or purely rule-based methods. To better understand the balance between stochasticity and determinism in biological processes a computational approach that incorporates both influences may afford additional insight into underlying biological mechanisms that give rise to emergent system properties. We apply a combined approach to the simulation and study of angiogenesis, the growth of new blood vessels from existing networks. This complex multicellular process begins with selection of an initiating endothelial cell, or tip cell, which sprouts from the parent vessels in response to stimulation by exogenous cues. We have constructed an agent-based model of sprouting angiogenesis to evaluate endothelial cell sprout initiation frequency and location, and we have experimentally validated it using high-resolution time-lapse confocal microscopy. ABM simulations were then compared to a Monte Carlo model, revealing that purely stochastic simulations could not generate sprout locations as accurately as the rule-informed agent-based model. These findings support the use of rule-based approaches for modeling the complex mechanisms underlying sprouting angiogenesis over purely stochastic methods.

Simulations of Quantum Turing Machines by Quantum Multi-Stack Machines

OpenAIRE

Qiu, Daowen

2005-01-01

As was well known, in classical computation, Turing machines, circuits, multi-stack machines, and multi-counter machines are equivalent, that is, they can simulate each other in polynomial time. In quantum computation, Yao [11] first proved that for any quantum Turing machines $M$, there exists quantum Boolean circuit $(n,t)$-simulating $M$, where $n$ denotes the length of input strings, and $t$ is the number of move steps before machine stopping. However, the simulations of quantum Turing ma...

3D Simulation of Multiple Simultaneous Hydraulic Fractures with Different Initial Lengths in Rock

Science.gov (United States)

Tang, X.; Rayudu, N. M.; Singh, G.

2017-12-01

Hydraulic fracturing is widely used technique for extracting shale gas. During this process, fractures with various initial lengths are induced in rock mass with hydraulic pressure. Understanding the mechanism of propagation and interaction between these induced hydraulic cracks is critical for optimizing the fracking process. In this work, numerical results are presented for investigating the effect of in-situ parameters and fluid properties on growth and interaction of multi simultaneous hydraulic fractures. A fully coupled 3D fracture simulator, TOUGH- GFEM is used for simulating the effect of different vital parameters, including in-situ stress, initial fracture length, fracture spacing, fluid viscosity and flow rate on induced hydraulic fractures growth. This TOUGH-GFEM simulator is based on 3D finite volume method (FVM) and partition of unity element method (PUM). Displacement correlation method (DCM) is used for calculating multi - mode (Mode I, II, III) stress intensity factors. Maximum principal stress criteria is used for crack propagation. Key words: hydraulic fracturing, TOUGH, partition of unity element method , displacement correlation method, 3D fracturing simulator

Simulation of the Initial 3-D Instability of an Impacting Drop Vortex Ring

DEFF Research Database (Denmark)

Sigurdson, Lorenz; Wiwchar, Justin; Walther, Jens Honore

2013-01-01

, a Rayleigh centrifugal instability, or a vortex breakdown-type instability. Simulations which simply have a perturbed solitary ring result in an instability similar to that seen experimentally. Waviness of the core which would be expected from a Widnall instability is not visible. Adding an opposite......-signed secondary vortex ring or an image vortex ring to the initial conditions, to trigger a Rayleigh or breakdown respectively, does not appear to significantly change the instability from what is seen with a solitary ring. This suggests that a Rayleigh or vortex breakdown-type instability are not likely at work......Computational vortex particle method simulations of a perturbed vortex ring are performed to recreate and understand the instability seen in impacting water drop experiments. Three fundamentally different initial vorticity distributions are used to attempt to trigger a Widnall instability...

The Microwave Properties of Simulated Melting Precipitation Particles: Sensitivity to Initial Melting

Science.gov (United States)

Johnson, B. T.; Olson, W. S.; Skofronick-Jackson, G.

2016-01-01

A simplified approach is presented for assessing the microwave response to the initial melting of realistically shaped ice particles. This paper is divided into two parts: (1) a description of the Single Particle Melting Model (SPMM), a heuristic melting simulation for ice-phase precipitation particles of any shape or size (SPMM is applied to two simulated aggregate snow particles, simulating melting up to 0.15 melt fraction by mass), and (2) the computation of the single-particle microwave scattering and extinction properties of these hydrometeors, using the discrete dipole approximation (via DDSCAT), at the following selected frequencies: 13.4, 35.6, and 94.0GHz for radar applications and 89, 165.0, and 183.31GHz for radiometer applications. These selected frequencies are consistent with current microwave remote-sensing platforms, such as CloudSat and the Global Precipitation Measurement (GPM) mission. Comparisons with calculations using variable-density spheres indicate significant deviations in scattering and extinction properties throughout the initial range of melting (liquid volume fractions less than 0.15). Integration of the single-particle properties over an exponential particle size distribution provides additional insight into idealized radar reflectivity and passive microwave brightness temperature sensitivity to variations in size/mass, shape, melt fraction, and particle orientation.

Image based SAR product simulation for analysis

Science.gov (United States)

Domik, G.; Leberl, F.

1987-01-01

SAR product simulation serves to predict SAR image gray values for various flight paths. Input typically consists of a digital elevation model and backscatter curves. A new method is described of product simulation that employs also a real SAR input image for image simulation. This can be denoted as 'image-based simulation'. Different methods to perform this SAR prediction are presented and advantages and disadvantages discussed. Ascending and descending orbit images from NASA's SIR-B experiment were used for verification of the concept: input images from ascending orbits were converted into images from a descending orbit; the results are compared to the available real imagery to verify that the prediction technique produces meaningful image data.

Beam simulations with initial bunch noise in superconducting RF proton linacs

CERN Document Server

Tückmantel, J

2010-01-01

Circular machines are plagued by coupled bunch instabilities (CBI), driven by impedance peaks, where then all cavity higher order modes (HOMs) are possible drivers. Limiting the CBI growth rate is the fundamental reason that all superconducting rf cavities in circular machines are equipped with HOM dampers. The question arises if for similar reasons HOM damping would not be imperative also in high current superconducting rf proton linacs. Therefore we have simulated the longitudinal bunched beam dynamics in such machines, also including charge and position noise on the injected bunches. Simulations were executed for a generic linac with properties close to the planned SPL at CERN, SNS, or Project X at FNAL. It was found that with strong bunch noise and monopole HOMs with high Qext large beam scatter, possibly exceeding the admittance of a receiving machine, cannot be excluded. A transverse simulation shows similar requirements. Therefore including initial bunch noise in any beam dynamic study on superconducti...

Annual Report: Carbon Capture Simulation Initiative (CCSI) (30 September 2013)

Energy Technology Data Exchange (ETDEWEB)

Miller, David C. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Syamlal, Madhava [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Cottrell, Roger [URS Corporation. (URS), San Francisco, CA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Kress, Joel D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sundaresan, S. [Princeton Univ., NJ (United States); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Storlie, C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bhattacharyya, D. [West Virginia Univ., Morgantown, WV (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Tong, Charles [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zitney, Stephen E [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Dale, Crystal [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Engel, Dave [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Agarwal, Deb [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Calafiura, Paolo [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shinn, John [SynPatEco, Pleasant Hill, CA (United States)

2013-09-30

The Carbon Capture Simulation Initiative (CCSI) is a partnership among national laboratories, industry and academic institutions that is developing and deploying state-of-the-art computational modeling and simulation tools to accelerate the commercialization of carbon capture technologies from discovery to development, demonstration, and ultimately the widespread deployment to hundreds of power plants. The CCSI Toolset will provide end users in industry with a comprehensive, integrated suite of scientifically validated models, with uncertainty quantification (UQ), optimization, risk analysis and decision making capabilities. The CCSI Toolset incorporates commercial and open-source software currently in use by industry and is also developing new software tools as necessary to fill technology gaps identified during execution of the project. Ultimately, the CCSI Toolset will (1) enable promising concepts to be more quickly identified through rapid computational screening of devices and processes; (2) reduce the time to design and troubleshoot new devices and processes; (3) quantify the technical risk in taking technology from laboratory-scale to commercial-scale; and (4) stabilize deployment costs more quickly by replacing some of the physical operational tests with virtual power plant simulations. CCSI is led by the National Energy Technology Laboratory (NETL) and leverages the Department of Energy (DOE) national laboratories’ core strengths in modeling and simulation, bringing together the best capabilities at NETL, Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Lawrence Livermore National Laboratory (LLNL), and Pacific Northwest National Laboratory (PNNL). The CCSI’s industrial partners provide representation from the power generation industry, equipment manufacturers, technology providers and engineering and construction firms. The CCSI’s academic participants (Carnegie Mellon University, Princeton University, West

Generation of initial kinetic distributions for simulation of long-pulse charged particle beams with high space-charge intensity

Directory of Open Access Journals (Sweden)

Steven M. Lund

2009-11-01

Full Text Available Self-consistent Vlasov-Poisson simulations of beams with high space-charge intensity often require specification of initial phase-space distributions that reflect properties of a beam that is well adapted to the transport channel—both in terms of low-order rms (envelope properties as well as the higher-order phase-space structure. Here, we first review broad classes of kinetic distributions commonly in use as initial Vlasov distributions in simulations of unbunched or weakly bunched beams with intense space-charge fields including the following: the Kapchinskij-Vladimirskij (KV equilibrium, continuous-focusing equilibria with specific detailed examples, and various nonequilibrium distributions, such as the semi-Gaussian distribution and distributions formed from specified functions of linear-field Courant-Snyder invariants. Important practical details necessary to specify these distributions in terms of standard accelerator inputs are presented in a unified format. Building on this presentation, a new class of approximate initial kinetic distributions are constructed using transformations that preserve linear focusing, single-particle Courant-Snyder invariants to map initial continuous-focusing equilibrium distributions to a form more appropriate for noncontinuous focusing channels. Self-consistent particle-in-cell simulations are employed to show that the approximate initial distributions generated in this manner are better adapted to the focusing channels for beams with high space-charge intensity. This improved capability enables simulations that more precisely probe intrinsic stability properties and machine performance.

Learning from Simulation Design to Develop Better Experiential Learning Initiatives: An Integrative Approach

Science.gov (United States)

Canhoto, Ana Isabel; Murphy, Jamie

2016-01-01

Simulations offer engaging learning experiences, via the provision of feedback or the opportunities for experimentation. However, they lack important attributes valued by marketing educators and employers. This article proposes a "back to basics" look at what constitutes an effective experiential learning initiative. Drawing on the…

Transients from initial conditions based on Lagrangian perturbation theory in N-body simulations II: the effect of the transverse mode

International Nuclear Information System (INIS)

Tatekawa, Takayuki

2014-01-01

We study the initial conditions for cosmological N-body simulations for precision cosmology. In general, Zel'dovich approximation has been applied for the initial conditions of N-body simulations for a long time. These initial conditions provide incorrect higher-order growth. These error caused by setting up the initial conditions by perturbation theory is called transients. We investigated the impact of transient on non-Gaussianity of density field by performing cosmological N-body simulations with initial conditions based on first-, second-, and third-order Lagrangian perturbation theory in previous paper. In this paper, we evaluates the effect of the transverse mode in the third-order Lagrangian perturbation theory for several statistical quantities such as power spectrum and non-Gaussianty. Then we clarified that the effect of the transverse mode in the third-order Lagrangian perturbation theory is quite small

Computer simulation in initial teacher education: a bridge across the faculty/practice divide or simply a better viewing platform?

OpenAIRE

Lowe, Graham

2011-01-01

This thesis reports on a mixed methods research project into the emerging area of computer simulation in Initial Teacher Education (ITE). Some areas where simulation has become a staple of initial or ongoing education and training, i.e. in health care and military applications, are examined to provide a context. The research explores the attitudes of a group of ITE students towards the use of a recently developed simulation tool and in particular considers the question of whether they view co...

Large-Scale Reactive Atomistic Simulation of Shock-induced Initiation Processes in Energetic Materials

Science.gov (United States)

Thompson, Aidan

2013-06-01

Initiation in energetic materials is fundamentally dependent on the interaction between a host of complex chemical and mechanical processes, occurring on scales ranging from intramolecular vibrations through molecular crystal plasticity up to hydrodynamic phenomena at the mesoscale. A variety of methods (e.g. quantum electronic structure methods (QM), non-reactive classical molecular dynamics (MD), mesoscopic continuum mechanics) exist to study processes occurring on each of these scales in isolation, but cannot describe how these processes interact with each other. In contrast, the ReaxFF reactive force field, implemented in the LAMMPS parallel MD code, allows us to routinely perform multimillion-atom reactive MD simulations of shock-induced initiation in a variety of energetic materials. This is done either by explicitly driving a shock-wave through the structure (NEMD) or by imposing thermodynamic constraints on the collective dynamics of the simulation cell e.g. using the Multiscale Shock Technique (MSST). These MD simulations allow us to directly observe how energy is transferred from the shockwave into other processes, including intramolecular vibrational modes, plastic deformation of the crystal, and hydrodynamic jetting at interfaces. These processes in turn cause thermal excitation of chemical bonds leading to initial chemical reactions, and ultimately to exothermic formation of product species. Results will be presented on the application of this approach to several important energetic materials, including pentaerythritol tetranitrate (PETN) and ammonium nitrate/fuel oil (ANFO). In both cases, we validate the ReaxFF parameterizations against QM and experimental data. For PETN, we observe initiation occurring via different chemical pathways, depending on the shock direction. For PETN containing spherical voids, we observe enhanced sensitivity due to jetting, void collapse, and hotspot formation, with sensitivity increasing with void size. For ANFO, we

Suppression of the initial transient in Monte Carlo criticality simulations

International Nuclear Information System (INIS)

Richet, Y.

2006-12-01

Criticality Monte Carlo calculations aim at estimating the effective multiplication factor (k-effective) for a fissile system through iterations simulating neutrons propagation (making a Markov chain). Arbitrary initialization of the neutron population can deeply bias the k-effective estimation, defined as the mean of the k-effective computed at each iteration. A simplified model of this cycle k-effective sequence is built, based on characteristics of industrial criticality Monte Carlo calculations. Statistical tests, inspired by Brownian bridge properties, are designed to discriminate stationarity of the cycle k-effective sequence. The initial detected transient is, then, suppressed in order to improve the estimation of the system k-effective. The different versions of this methodology are detailed and compared, firstly on a plan of numerical tests fitted on criticality Monte Carlo calculations, and, secondly on real criticality calculations. Eventually, the best methodologies observed in these tests are selected and allow to improve industrial Monte Carlo criticality calculations. (author)

Annual Report: Carbon Capture Simulation Initiative (CCSI) (30 September 2012)

Energy Technology Data Exchange (ETDEWEB)

Miller, David C. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Syamlal, Madhava [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Cottrell, Roger [URS Corporation. (URS), San Francisco, CA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Kress, Joel D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sundaresan, S. [Princeton Univ., NJ (United States); Sahinidis, Nikolaos V. [Carnegie Mellon Univ., Pittsburgh, PA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Zitney, Stephen E. [NETL; Bhattacharyya, D. [West Virginia Univ., Morgantown, WV (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Agarwal, Deb [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tong, Charles [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lin, Guang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dale, Crystal [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Engel, Dave [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Calafiura, Paolo [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Beattie, Keith [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shinn, John [SynPatEco. Pleasant Hill, CA (United States)

2012-09-30

The Carbon Capture Simulation Initiative (CCSI) is a partnership among national laboratories, industry and academic institutions that is developing and deploying state-of-the-art computational modeling and simulation tools to accelerate the commercialization of carbon capture technologies from discovery to development, demonstration, and ultimately the widespread deployment to hundreds of power plants. The CCSI Toolset will provide end users in industry with a comprehensive, integrated suite of scientifically validated models, with uncertainty quantification (UQ), optimization, risk analysis and decision making capabilities. The CCSI Toolset incorporates commercial and open-source software currently in use by industry and is also developing new software tools as necessary to fill technology gaps identified during execution of the project. Ultimately, the CCSI Toolset will (1) enable promising concepts to be more quickly identified through rapid computational screening of devices and processes; (2) reduce the time to design and troubleshoot new devices and processes; (3) quantify the technical risk in taking technology from laboratory-scale to commercial-scale; and (4) stabilize deployment costs more quickly by replacing some of the physical operational tests with virtual power plant simulations. CCSI is organized into 8 technical elements that fall under two focus areas. The first focus area (Physicochemical Models and Data) addresses the steps necessary to model and simulate the various technologies and processes needed to bring a new Carbon Capture and Storage (CCS) technology into production. The second focus area (Analysis & Software) is developing the software infrastructure to integrate the various components and implement the tools that are needed to make quantifiable decisions regarding the viability of new CCS technologies. CCSI also has an Industry Advisory Board (IAB). By working closely with industry from the inception of the project to identify

Numerical simulation of Hanford Tank 241-SY-101 jet initiated fluid dynamics

International Nuclear Information System (INIS)

Trent, D.S.; Michener, T.E.

1994-01-01

The episodic Gas Release Events (GREs) that have characterized the behavior of Hanford tank 241-SY-101 for the past several years are thought to result from the entrapment of gases generated in the settled solids, i.e., sludge, layer of the tank. Gases consisting of about 36% hydrogen by volume, which are generated by complicated and poorly understood radiological and chemical processes, are apparently trapped in the settled solids layer until their accumulation initiates a buoyant upset of this layer, abruptly releasing large quantities of gas. Once concept for preventing the gas accumulation is to mobilize the settled materials with jet mixing. It is suggested that continual agitation of the settled solids using a mixer pump would free the gas bubbles so that they could continually escape, thus mitigating the potential for accumulation of flammable concentrations of hydrogen in the tank dome space following a GRE. A pump test is planned to evaluate the effectiveness of the jet mixing mitigation concept. The pump will circulate liquid from the upper layer of the tank, discharging it through two horizontal jets located approximately 2 1/2 ft above the tank floor. To prepare for start-up of this pump test, technical, operation, and safety questions concerning an anticipated gas release were addressed by numerical simulation using the TEMPEST computer code. Simulations of the pump initiated gas release revealed that the amount of gas that could potentially be released to the tank dome space is very sensitive to the initial conditions assumed for the amount and distribution of gas in the sludge layer. Calculations revealed that within the assumptions regarding gas distribution and content, the pump might initiate a rollover--followed by a significant gas release--if the sludge layer contains more than about 13 to 14% gas distributed with constant volume fraction

Initial conditions for cosmological N-body simulations of the scalar sector of theories of Newtonian, Relativistic and Modified Gravity

International Nuclear Information System (INIS)

Valkenburg, Wessel; Hu, Bin

2015-01-01

We present a description for setting initial particle displacements and field values for simulations of arbitrary metric theories of gravity, for perfect and imperfect fluids with arbitrary characteristics. We extend the Zel'dovich Approximation to nontrivial theories of gravity, and show how scale dependence implies curved particle paths, even in the entirely linear regime of perturbations. For a viable choice of Effective Field Theory of Modified Gravity, initial conditions set at high redshifts are affected at the level of up to 5% at Mpc scales, which exemplifies the importance of going beyond Λ-Cold Dark Matter initial conditions for modifications of gravity outside of the quasi-static approximation. In addition, we show initial conditions for a simulation where a scalar modification of gravity is modelled in a Lagrangian particle-like description. Our description paves the way for simulations and mock galaxy catalogs under theories of gravity beyond the standard model, crucial for progress towards precision tests of gravity and cosmology

Evolvement simulation of the probability of neutron-initiating persistent fission chain

International Nuclear Information System (INIS)

Wang Zhe; Hong Zhenying

2014-01-01

Background: Probability of neutron-initiating persistent fission chain, which has to be calculated in analysis of critical safety, start-up of reactor, burst waiting time on pulse reactor, bursting time on pulse reactor, etc., is an inherent parameter in a multiplying assembly. Purpose: We aim to derive time-dependent integro-differential equation for such probability in relative velocity space according to the probability conservation, and develop the deterministic code Dynamic Segment Number Probability (DSNP) based on the multi-group S N method. Methods: The reliable convergence of dynamic calculation was analyzed and numerical simulation of the evolvement process of dynamic probability for varying concentration was performed under different initial conditions. Results: On Highly Enriched Uranium (HEU) Bare Spheres, when the time is long enough, the results of dynamic calculation approach to those of static calculation. The most difference of such results between DSNP and Partisn code is less than 2%. On Baker model, over the range of about 1 μs after the first criticality, the most difference between the dynamic and static calculation is about 300%. As for a super critical system, the finite fission chains decrease and the persistent fission chains increase as the reactivity aggrandizes, the dynamic evolvement curve of initiation probability is close to the static curve within the difference of 5% when the K eff is more than 1.2. The cumulative probability curve also indicates that the difference of integral results between the dynamic calculation and the static calculation decreases from 35% to 5% as the K eff increases. This demonstrated that the ability of initiating a self-sustaining fission chain reaction approaches stabilization, while the former difference (35%) showed the important difference of the dynamic results near the first criticality with the static ones. The DSNP code agrees well with Partisn code. Conclusions: There are large numbers of

A Simulation-Based Quality Improvement Initiative Improves Pediatric Readiness in Community Hospitals.

Science.gov (United States)

Whitfill, Travis; Gawel, Marcie; Auerbach, Marc

2017-07-17

The National Pediatric Readiness Project Pediatric Readiness Survey (PRS) measured pediatric readiness in 4149 US emergency departments (EDs) and noted an average score of 69 on a 100-point scale. This readiness score consists of 6 domains: coordination of pediatric patient care (19/100), physician/nurse staffing and training (10/100), quality improvement activities (7/100), patient safety initiatives (14/100), policies and procedures (17/100), and availability of pediatric equipment (33/100). We aimed to assess and improve pediatric emergency readiness scores across Connecticut's hospitals. The aim of this study was to compare the National Pediatric Readiness Project readiness score before and after an in situ simulation-based assessment and quality improvement program in Connecticut hospitals. We leveraged in situ simulations to measure the quality of resuscitative care provided by interprofessional teams to 3 simulated patients (infant septic shock, infant seizure, and child cardiac arrest) presenting to their ED resuscitation bay. Assessments of EDs were made based on a composite quality score that was measured as the sum of 4 distinct domains: (1) adherence to sepsis guidelines, (2) adherence to cardiac arrest guidelines, (3) performance on seizure resuscitation, and (4) teamwork. After the simulation, a detailed report with scores, comparisons to other EDs, and a gap analysis were provided to sites. Based on this report, a regional children's hospital team worked collaboratively with each ED to develop action items and a timeline for improvements. The National Pediatric Readiness Project PRS scores, the primary outcome of this study, were measured before and after participation. Twelve community EDs in Connecticut participated in this project. The PRS scores were assessed before and after the intervention (simulation-based assessment and gap analysis/report-out). The average time between PRS assessments was 21 months. The PRS scores significantly improved 12

High-Resolution Mesoscale Simulations of the 6-7 May 2000 Missouri Flash Flood: Impact of Model Initialization and Land Surface Treatment

Science.gov (United States)

Baker, R. David; Wang, Yansen; Tao, Wei-Kuo; Wetzel, Peter; Belcher, Larry R.

2004-01-01

High-resolution mesoscale model simulations of the 6-7 May 2000 Missouri flash flood event were performed to test the impact of model initialization and land surface treatment on timing, intensity, and location of extreme precipitation. In this flash flood event, a mesoscale convective system (MCS) produced over 340 mm of rain in roughly 9 hours in some locations. Two different types of model initialization were employed: 1) NCEP global reanalysis with 2.5-degree grid spacing and 12-hour temporal resolution, and 2) Eta reanalysis with 40- km grid spacing and $hour temporal resolution. In addition, two different land surface treatments were considered. A simple land scheme. (SLAB) keeps soil moisture fixed at initial values throughout the simulation, while a more sophisticated land model (PLACE) allows for r interactive feedback. Simulations with high-resolution Eta model initialization show considerable improvement in the intensity of precipitation due to the presence in the initialization of a residual mesoscale convective vortex (hlCV) from a previous MCS. Simulations with the PLACE land model show improved location of heavy precipitation. Since soil moisture can vary over time in the PLACE model, surface energy fluxes exhibit strong spatial gradients. These surface energy flux gradients help produce a strong low-level jet (LLJ) in the correct location. The LLJ then interacts with the cold outflow boundary of the MCS to produce new convective cells. The simulation with both high-resolution model initialization and time-varying soil moisture test reproduces the intensity and location of observed rainfall.

Simulation of surface crack initiation induced by slip localization and point defects kinetics

International Nuclear Information System (INIS)

Sauzay, Maxime; Liu, Jia; Rachdi, Fatima

2014-01-01

Crack initiation along surface persistent slip bands (PSBs) has been widely observed and modelled. Nevertheless, from our knowledge, no physically-based fracture modelling has been proposed and validated with respect to the numerous recent experimental data showing the strong relationship between extrusion and microcrack initiation. The whole FE modelling accounts for: - localized plastic slip in PSBs; - production and annihilation of vacancies induced by cyclic slip. If temperature is high enough, point defects may diffuse in the surrounding matrix due to large concentration gradients, allowing continuous extrusion growth in agreement with Polak's model. At each cycle, the additional atoms diffusing from the matrix are taken into account by imposing an incremental free dilatation; - brittle fracture at the interfaces between PSBs and their surrounding matrix which is simulated using cohesive zone modelling. Any inverse fitting of parameter is avoided. Only experimental single crystal data are used such as hysteresis loops and resistivity values. Two fracture parameters are required: the {111} surface energy which depends on environment and the cleavage stress which is predicted by the universal binding energy relationship. The predicted extrusion growth curves agree rather well with the experimental data published for copper and the 316L steel. A linear dependence with respect to PSB length, thickness and slip plane angle is predicted in agreement with recent AFM measurement results. Crack initiation simulations predict fairly well the effects of PSB length and environment for copper single and poly-crystals. (authors)

High-resolution simulations of cylindrical void collapse in energetic materials: Effect of primary and secondary collapse on initiation thresholds

Science.gov (United States)

Rai, Nirmal Kumar; Schmidt, Martin J.; Udaykumar, H. S.

2017-04-01

Void collapse in energetic materials leads to hot spot formation and enhanced sensitivity. Much recent work has been directed towards simulation of collapse-generated reactive hot spots. The resolution of voids in calculations to date has varied as have the resulting predictions of hot spot intensity. Here we determine the required resolution for reliable cylindrical void collapse calculations leading to initiation of chemical reactions. High-resolution simulations of collapse provide new insights into the mechanism of hot spot generation. It is found that initiation can occur in two different modes depending on the loading intensity: Either the initiation occurs due to jet impact at the first collapse instant or it can occur at secondary lobes at the periphery of the collapsed void. A key observation is that secondary lobe collapse leads to large local temperatures that initiate reactions. This is due to a combination of a strong blast wave from the site of primary void collapse and strong colliding jets and vortical flows generated during the collapse of the secondary lobes. The secondary lobe collapse results in a significant lowering of the predicted threshold for ignition of the energetic material. The results suggest that mesoscale simulations of void fields may suffer from significant uncertainty in threshold predictions because unresolved calculations cannot capture the secondary lobe collapse phenomenon. The implications of this uncertainty for mesoscale simulations are discussed in this paper.

Large-scale tropospheric transport in the Chemistry-Climate Model Initiative (CCMI) simulations

Science.gov (United States)

Orbe, Clara; Yang, Huang; Waugh, Darryn W.; Zeng, Guang; Morgenstern, Olaf; Kinnison, Douglas E.; Lamarque, Jean-Francois; Tilmes, Simone; Plummer, David A.; Scinocca, John F.; Josse, Beatrice; Marecal, Virginie; Jöckel, Patrick; Oman, Luke D.; Strahan, Susan E.; Deushi, Makoto; Tanaka, Taichu Y.; Yoshida, Kohei; Akiyoshi, Hideharu; Yamashita, Yousuke; Stenke, Andreas; Revell, Laura; Sukhodolov, Timofei; Rozanov, Eugene; Pitari, Giovanni; Visioni, Daniele; Stone, Kane A.; Schofield, Robyn; Banerjee, Antara

2018-05-01

Understanding and modeling the large-scale transport of trace gases and aerosols is important for interpreting past (and projecting future) changes in atmospheric composition. Here we show that there are large differences in the global-scale atmospheric transport properties among the models participating in the IGAC SPARC Chemistry-Climate Model Initiative (CCMI). Specifically, we find up to 40 % differences in the transport timescales connecting the Northern Hemisphere (NH) midlatitude surface to the Arctic and to Southern Hemisphere high latitudes, where the mean age ranges between 1.7 and 2.6 years. We show that these differences are related to large differences in vertical transport among the simulations, in particular to differences in parameterized convection over the oceans. While stronger convection over NH midlatitudes is associated with slower transport to the Arctic, stronger convection in the tropics and subtropics is associated with faster interhemispheric transport. We also show that the differences among simulations constrained with fields derived from the same reanalysis products are as large as (and in some cases larger than) the differences among free-running simulations, most likely due to larger differences in parameterized convection. Our results indicate that care must be taken when using simulations constrained with analyzed winds to interpret the influence of meteorology on tropospheric composition.

Large-scale tropospheric transport in the Chemistry–Climate Model Initiative (CCMI simulations

Directory of Open Access Journals (Sweden)

C. Orbe

2018-05-01

Full Text Available Understanding and modeling the large-scale transport of trace gases and aerosols is important for interpreting past (and projecting future changes in atmospheric composition. Here we show that there are large differences in the global-scale atmospheric transport properties among the models participating in the IGAC SPARC Chemistry–Climate Model Initiative (CCMI. Specifically, we find up to 40 % differences in the transport timescales connecting the Northern Hemisphere (NH midlatitude surface to the Arctic and to Southern Hemisphere high latitudes, where the mean age ranges between 1.7 and 2.6 years. We show that these differences are related to large differences in vertical transport among the simulations, in particular to differences in parameterized convection over the oceans. While stronger convection over NH midlatitudes is associated with slower transport to the Arctic, stronger convection in the tropics and subtropics is associated with faster interhemispheric transport. We also show that the differences among simulations constrained with fields derived from the same reanalysis products are as large as (and in some cases larger than the differences among free-running simulations, most likely due to larger differences in parameterized convection. Our results indicate that care must be taken when using simulations constrained with analyzed winds to interpret the influence of meteorology on tropospheric composition.

Modeling, simulation, and optimal initiation planning for needle insertion into the liver.

Science.gov (United States)

Sharifi Sedeh, R; Ahmadian, M T; Janabi-Sharifi, F

2010-04-01

Needle insertion simulation and planning systems (SPSs) will play an important role in diminishing inappropriate insertions into soft tissues and resultant complications. Difficulties in SPS development are due in large part to the computational requirements of the extensive calculations in finite element (FE) models of tissue. For clinical feasibility, the computational speed of SPSs must be improved. At the same time, a realistic model of tissue properties that reflects large and velocity-dependent deformations must be employed. The purpose of this study is to address the aforementioned difficulties by presenting a cost-effective SPS platform for needle insertions into the liver. The study was constrained to planar (2D) cases, but can be extended to 3D insertions. To accommodate large and velocity-dependent deformations, a hyperviscoelastic model was devised to produce an FE model of liver tissue. Material constants were identified by a genetic algorithm applied to the experimental results of unconfined compressions of bovine liver. The approach for SPS involves B-spline interpolations of sample data generated from the FE model of liver. Two interpolation-based models are introduced to approximate puncture times and to approximate the coordinates of FE model nodes interacting with the needle tip as a function of the needle initiation pose; the latter was also a function of postpuncture time. A real-time simulation framework is provided, and its computational benefit is highlighted by comparing its performance with the FE method. A planning algorithm for optimal needle initiation was designed, and its effectiveness was evaluated by analyzing its accuracy in reaching a random set of targets at different resolutions of sampled data using the FE model. The proposed simulation framework can easily surpass haptic rates (>500 Hz), even with a high pose resolution level ( approximately 30). The computational time required to update the coordinates of the node at the

The halo bispectrum in N-body simulations with non-Gaussian initial conditions

Science.gov (United States)

Sefusatti, E.; Crocce, M.; Desjacques, V.

2012-10-01

We present measurements of the bispectrum of dark matter haloes in numerical simulations with non-Gaussian initial conditions of local type. We show, in the first place, that the overall effect of primordial non-Gaussianity on the halo bispectrum is larger than on the halo power spectrum when all measurable configurations are taken into account. We then compare our measurements with a tree-level perturbative prediction, finding good agreement at large scales when the constant Gaussian bias parameter, both linear and quadratic, and their constant non-Gaussian corrections are fitted for. The best-fitting values of the Gaussian bias factors and their non-Gaussian, scale-independent corrections are in qualitative agreement with the peak-background split expectations. In particular, we show that the effect of non-Gaussian initial conditions on squeezed configurations is fairly large (up to 30 per cent for fNL = 100 at redshift z = 0.5) and results from contributions of similar amplitude induced by the initial matter bispectrum, scale-dependent bias corrections as well as from non-linear matter bispectrum corrections. We show, in addition, that effects at second order in fNL are irrelevant for the range of values allowed by cosmic microwave background and galaxy power spectrum measurements, at least on the scales probed by our simulations (k > 0.01 h Mpc-1). Finally, we present a Fisher matrix analysis to assess the possibility of constraining primordial non-Gaussianity with future measurements of the galaxy bispectrum. We find that a survey with a volume of about 10 h-3 Gpc3 at mean redshift z ≃ 1 could provide an error on fNL of the order of a few. This shows the relevance of a joint analysis of galaxy power spectrum and bispectrum in future redshift surveys.

On the importance of an accurate representation of the initial state of the system in classical dynamics simulations

Science.gov (United States)

García-Vela, A.

2000-05-01

A definition of a quantum-type phase-space distribution is proposed in order to represent the initial state of the system in a classical dynamics simulation. The central idea is to define an initial quantum phase-space state of the system as the direct product of the coordinate and momentum representations of the quantum initial state. The phase-space distribution is then obtained as the square modulus of this phase-space state. The resulting phase-space distribution closely resembles the quantum nature of the system initial state. The initial conditions are sampled with the distribution, using a grid technique in phase space. With this type of sampling the distribution of initial conditions reproduces more faithfully the shape of the original phase-space distribution. The method is applied to generate initial conditions describing the three-dimensional state of the Ar-HCl cluster prepared by ultraviolet excitation. The photodissociation dynamics is simulated by classical trajectories, and the results are compared with those of a wave packet calculation. The classical and quantum descriptions are found in good agreement for those dynamical events less subject to quantum effects. The classical result fails to reproduce the quantum mechanical one for the more strongly quantum features of the dynamics. The properties and applicability of the phase-space distribution and the sampling technique proposed are discussed.

Fluids density functional theory and initializing molecular dynamics simulations of block copolymers

Science.gov (United States)

Brown, Jonathan R.; Seo, Youngmi; Maula, Tiara Ann D.; Hall, Lisa M.

2016-03-01

Classical, fluids density functional theory (fDFT), which can predict the equilibrium density profiles of polymeric systems, and coarse-grained molecular dynamics (MD) simulations, which are often used to show both structure and dynamics of soft materials, can be implemented using very similar bead-based polymer models. We aim to use fDFT and MD in tandem to examine the same system from these two points of view and take advantage of the different features of each methodology. Additionally, the density profiles resulting from fDFT calculations can be used to initialize the MD simulations in a close to equilibrated structure, speeding up the simulations. Here, we show how this method can be applied to study microphase separated states of both typical diblock and tapered diblock copolymers in which there is a region with a gradient in composition placed between the pure blocks. Both methods, applied at constant pressure, predict a decrease in total density as segregation strength or the length of the tapered region is increased. The predictions for the density profiles from fDFT and MD are similar across materials with a wide range of interfacial widths.

Simulation of the induction of oxidation of low-density lipoprotein by high copper concentrations: evidence for a nonconstant rate of initiation.

Science.gov (United States)

Abuja, P M; Albertini, R; Esterbauer, H

1997-06-01

Kinetic simulation can help obtain deeper insight into the molecular mechanisms of complex processes, such as lipid peroxidation (LPO) in low-density lipoprotein (LDL). We have previously set up a single-compartment model of this process, initiating with radicals generated externally at a constant rate to show the interplay of radical scavenging and chain propagation. Here we focus on the initiating events, substituting constant rate of initiation (Ri) by redox cycling of Cu2+ and Cu+. Our simulation reveals that early events in copper-mediated LDL oxidation include (1) the reduction of Cu2+ by tocopherol (TocOH) which generates tocopheroxyl radical (TocO.), (2) the fate of TocO. which either is recycled or recombines with lipid peroxyl radical (LOO.), and (3) the reoxidation of Cu+ by lipid hydroperoxide which results in alkoxyl radical (LO.) formation. So TocO., LOO., and LO. can be regarded as primordial radicals, and the sum of their formation rates is the total rate of initiation, Ri. As experimental information of these initiating events cannot be obtained experimentally, the whole model was validated experimentally by comparison of LDL oxidation in the presence and absence of bathocuproine as predicted by simulation. Simulation predicts that Ri decreases by 2 orders of magnitude during lag time. This has important consequences for the estimation of oxidation resistance in copper-mediated LDL oxidation: after consumption of tocopherol, even small amounts of antioxidants may prolong the lag phase for a considerable time.

Lattice Boltzmann simulation of shear-induced particle migration in plane Couette-Poiseuille flow: Local ordering of suspension

Science.gov (United States)

Chun, Byoungjin; Kwon, Ilyoung; Jung, Hyun Wook; Hyun, Jae Chun

2017-12-01

The shear-induced migration of concentrated non-Brownian monodisperse suspensions in combined plane Couette-Poiseuille (C-P) flows is studied using a lattice Boltzmann simulation. The simulations are mainly performed for a particle volume fraction of ϕbulk = 0.4 and H/a = 44.3, 23.3, where H and a denote the channel height and radius of suspended particles, respectively. The simulation method is validated in two simple flows, plane Poiseuille and plane Couette flows. In the Poiseuille flow, particles migrate to the mid-plane of the channel where the local concentration is close to the limit of random-close-packing, and a random structure is also observed at the plane. In the Couette flow, the particle distribution remains in the initial uniform distribution. In the combined C-P flows, the behaviors of migration are categorized into three groups, namely, Poiseuille-dominant, Couette-dominant, and intermediate regimes, based on the value of a characteristic force, G, where G denotes the relative magnitude of the body force (P) against the wall-driving force (C). With respect to the Poiseuille-dominant regime, the location of the maximum concentration is shifted from the mid-plane to the lower wall moving in the same direction as the external body force, when G decreases. With respect to the Couette-dominant regime, the behavior is similar to that of a simple shear flow with the exception that a slightly higher concentration of particles is observed near the lower wall. However, with respect to the intermediate value of G, several layers of highly ordered particles are unexpectedly observed near the lower wall where the plane of maximum concentration is located. The locally ordered structure is mainly due to the lateral migration of particles and wall confinement. The suspended particles migrate toward a vanishingly small shear rate at the wall, and they are consequently layered into highly ordered two-dimensional structures at the high local volume fraction.

Initial condition effects on large scale structure in numerical simulations of plane mixing layers

Science.gov (United States)

McMullan, W. A.; Garrett, S. J.

2016-01-01

In this paper, Large Eddy Simulations are performed on the spatially developing plane turbulent mixing layer. The simulated mixing layers originate from initially laminar conditions. The focus of this research is on the effect of the nature of the imposed fluctuations on the large-scale spanwise and streamwise structures in the flow. Two simulations are performed; one with low-level three-dimensional inflow fluctuations obtained from pseudo-random numbers, the other with physically correlated fluctuations of the same magnitude obtained from an inflow generation technique. Where white-noise fluctuations provide the inflow disturbances, no spatially stationary streamwise vortex structure is observed, and the large-scale spanwise turbulent vortical structures grow continuously and linearly. These structures are observed to have a three-dimensional internal geometry with branches and dislocations. Where physically correlated provide the inflow disturbances a "streaky" streamwise structure that is spatially stationary is observed, with the large-scale turbulent vortical structures growing with the square-root of time. These large-scale structures are quasi-two-dimensional, on top of which the secondary structure rides. The simulation results are discussed in the context of the varying interpretations of mixing layer growth that have been postulated. Recommendations are made concerning the data required from experiments in order to produce accurate numerical simulation recreations of real flows.

A reappraisal of drug release laws using Monte Carlo simulations: the prevalence of the Weibull function.

Science.gov (United States)

Kosmidis, Kosmas; Argyrakis, Panos; Macheras, Panos

2003-07-01

To verify the Higuchi law and study the drug release from cylindrical and spherical matrices by means of Monte Carlo computer simulation. A one-dimensional matrix, based on the theoretical assumptions of the derivation of the Higuchi law, was simulated and its time evolution was monitored. Cylindrical and spherical three-dimensional lattices were simulated with sites at the boundary of the lattice having been denoted as leak sites. Particles were allowed to move inside it using the random walk model. Excluded volume interactions between the particles was assumed. We have monitored the system time evolution for different lattice sizes and different initial particle concentrations. The Higuchi law was verified using the Monte Carlo technique in a one-dimensional lattice. It was found that Fickian drug release from cylindrical matrices can be approximated nicely with the Weibull function. A simple linear relation between the Weibull function parameters and the specific surface of the system was found. Drug release from a matrix, as a result of a diffusion process assuming excluded volume interactions between the drug molecules, can be described using a Weibull function. This model, although approximate and semiempirical, has the benefit of providing a simple physical connection between the model parameters and the system geometry, which was something missing from other semiempirical models.

Molecular dynamics simulations of the diffusion and coalescence of helium in tungsten

Energy Technology Data Exchange (ETDEWEB)

Zhou, Y.L. [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Department of Physics, Guangxi University, Nanning 530004 (China); Wang, J. [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Hou, Q., E-mail: qhou@scu.edu.cn [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Deng, A.H. [Department of Physics, Sichuan University, Chengdu 610064 (China)

2014-03-15

Molecular dynamics (MD) simulations are performed on the diffusion and coalescence of helium in tungsten. A new method for determining the effective capture radii (ECRs) and the dissociation energies of helium-related defects is proposed in this work. It is observed that the ECR of an interstitial helium atom trapping helium interstitials (denoted as He–He{sub n}, n = 1–3) decreases with increasing temperature, except for He–He{sub 2} at T < 400 K. The traditional view that the ECR is approximately equal to the lattice constant, which has been widely used in kinetic Monte Carlo (KMC) and rate theory (RT) models, is only valid in some cases. However, the ECR between an interstitial helium atom and a substitutional helium atom (denoted as He–HeV) always approximates the third nearest-neighbor tetrahedral positions of the HeV. The diffusion coefficients D{sub n} for helium clusters are also investigated. He{sub 2} migrates more quickly than a single He atom does at T < 400 K, whereas the diffusion path of He{sub 2} changes at higher temperatures. Another counterintuitive observation is that D{sub 5} > D{sub 3} > D{sub 4} at T < 500 K, which can be attributed to the disordered structure of He{sub 5}. The Arrhenius relation describes the diffusion of He{sub n} well in the temperature range from 300 K to 550 K, whereas the diffusion is not a standard thermally activated process at higher temperatures. Taken together, these results help elucidate the initial stage of helium bubble formation in tungsten as well as the requirements of long-term evolution methods such as KMC or RT models.

The Ozone Budget in the Upper Troposphere from Global Modeling Initiative (GMI)Simulations

Science.gov (United States)

Rodriquez, J.; Duncan, Bryan N.; Logan, Jennifer A.

2006-01-01

Ozone concentrations in the upper troposphere are influenced by in-situ production, long-range tropospheric transport, and influx of stratospheric ozone, as well as by photochemical removal. Since ozone is an important greenhouse gas in this region, it is particularly important to understand how it will respond to changes in anthropogenic emissions and changes in stratospheric ozone fluxes.. This response will be determined by the relative balance of the different production, loss and transport processes. Ozone concentrations calculated by models will differ depending on the adopted meteorological fields, their chemical scheme, anthropogenic emissions, and treatment of the stratospheric influx. We performed simulations using the chemical-transport model from the Global Modeling Initiative (GMI) with meteorological fields from (It)h e NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), (2) the atmospheric GCM from NASA's Global Modeling and Assimilation Office(GMAO), and (3) assimilated winds from GMAO . These simulations adopt the same chemical mechanism and emissions, and adopt the Synthetic Ozone (SYNOZ) approach for treating the influx of stratospheric ozone -. In addition, we also performed simulations for a coupled troposphere-stratosphere model with a subset of the same winds. Simulations were done for both 4degx5deg and 2degx2.5deg resolution. Model results are being tested through comparison with a suite of atmospheric observations. In this presentation, we diagnose the ozone budget in the upper troposphere utilizing the suite of GMI simulations, to address the sensitivity of this budget to: a) the different meteorological fields used; b) the adoption of the SYNOZ boundary condition versus inclusion of a full stratosphere; c) model horizontal resolution. Model results are compared to observations to determine biases in particular simulations; by examining these comparisons in conjunction with the derived budgets, we may pinpoint

Performance analyses of naval ships based on engineering level of simulation at the initial design stage

Directory of Open Access Journals (Sweden)

Dong-Hoon Jeong

2017-07-01

Full Text Available Naval ships are assigned many and varied missions. Their performance is critical for mission success, and depends on the specifications of the components. This is why performance analyses of naval ships are required at the initial design stage. Since the design and construction of naval ships take a very long time and incurs a huge cost, Modeling and Simulation (M & S is an effective method for performance analyses. Thus in this study, a simulation core is proposed to analyze the performance of naval ships considering their specifications. This simulation core can perform the engineering level of simulations, considering the mathematical models for naval ships, such as maneuvering equations and passive sonar equations. Also, the simulation models of the simulation core follow Discrete EVent system Specification (DEVS and Discrete Time System Specification (DTSS formalisms, so that simulations can progress over discrete events and discrete times. In addition, applying DEVS and DTSS formalisms makes the structure of simulation models flexible and reusable. To verify the applicability of this simulation core, such a simulation core was applied to simulations for the performance analyses of a submarine in an Anti-SUrface Warfare (ASUW mission. These simulations were composed of two scenarios. The first scenario of submarine diving carried out maneuvering performance analysis by analyzing the pitch angle variation and depth variation of the submarine over time. The second scenario of submarine detection carried out detection performance analysis by analyzing how well the sonar of the submarine resolves adjacent targets. The results of these simulations ensure that the simulation core of this study could be applied to the performance analyses of naval ships considering their specifications.

Molecular dynamics simulations of the diffusion and coalescence of helium in tungsten

International Nuclear Information System (INIS)

Zhou, Y.L.; Wang, J.; Hou, Q.; Deng, A.H.

2014-01-01

Molecular dynamics (MD) simulations are performed on the diffusion and coalescence of helium in tungsten. A new method for determining the effective capture radii (ECRs) and the dissociation energies of helium-related defects is proposed in this work. It is observed that the ECR of an interstitial helium atom trapping helium interstitials (denoted as He–He n , n = 1–3) decreases with increasing temperature, except for He–He 2 at T n for helium clusters are also investigated. He 2 migrates more quickly than a single He atom does at T 2 changes at higher temperatures. Another counterintuitive observation is that D 5 > D 3 > D 4 at T 5 . The Arrhenius relation describes the diffusion of He n well in the temperature range from 300 K to 550 K, whereas the diffusion is not a standard thermally activated process at higher temperatures. Taken together, these results help elucidate the initial stage of helium bubble formation in tungsten as well as the requirements of long-term evolution methods such as KMC or RT models

A simulation model to estimate the cost and effectiveness of alternative dialysis initiation strategies.

Science.gov (United States)

Lee, Chris P; Chertow, Glenn M; Zenios, Stefanos A

2006-01-01

Patients with end-stage renal disease (ESRD) require dialysis to maintain survival. The optimal timing of dialysis initiation in terms of cost-effectiveness has not been established. We developed a simulation model of individuals progressing towards ESRD and requiring dialysis. It can be used to analyze dialysis strategies and scenarios. It was embedded in an optimization frame worked to derive improved strategies. Actual (historical) and simulated survival curves and hospitalization rates were virtually indistinguishable. The model overestimated transplantation costs (10%) but it was related to confounding by Medicare coverage. To assess the model's robustness, we examined several dialysis strategies while input parameters were perturbed. Under all 38 scenarios, relative rankings remained unchanged. An improved policy for a hypothetical patient was derived using an optimization algorithm. The model produces reliable results and is robust. It enables the cost-effectiveness analysis of dialysis strategies.

Modeling initial contact dynamics during ambulation with dynamic simulation.

Science.gov (United States)

Meyer, Andrew R; Wang, Mei; Smith, Peter A; Harris, Gerald F

2007-04-01

Ankle-foot orthoses are frequently used interventions to correct pathological gait. Their effects on the kinematics and kinetics of the proximal joints are of great interest when prescribing ankle-foot orthoses to specific patient groups. Mathematical Dynamic Model (MADYMO) is developed to simulate motor vehicle crash situations and analyze tissue injuries of the occupants based multibody dynamic theories. Joint kinetics output from an inverse model were perturbed and input to the forward model to examine the effects of changes in the internal sagittal ankle moment on knee and hip kinematics following heel strike. Increasing the internal ankle moment (augmentation, equivalent to gastroc-soleus contraction) produced less pronounced changes in kinematic results at the hip, knee and ankle than decreasing the moment (attenuation, equivalent to gastroc-soleus relaxation). Altering the internal ankle moment produced two distinctly different kinematic curve morphologies at the hip. Decreased internal ankle moments increased hip flexion, peaking at roughly 8% of the gait cycle. Increasing internal ankle moments decreased hip flexion to a lesser degree, and approached normal at the same point in the gait cycle. Increasing the internal ankle moment produced relatively small, well-behaved extension-biased kinematic results at the knee. Decreasing the internal ankle moment produced more substantial changes in knee kinematics towards flexion that increased with perturbation magnitude. Curve morphologies were similar to those at the hip. Immediately following heel strike, kinematic results at the ankle showed movement in the direction of the internal moment perturbation. Increased internal moments resulted in kinematic patterns that rapidly approach normal after initial differences. When the internal ankle moment was decreased, differences from normal were much greater and did not rapidly decrease. This study shows that MADYMO can be successfully applied to accomplish forward

Simulation of plume dynamics by the Lattice Boltzmann Method

Science.gov (United States)

Mora, Peter; Yuen, David A.

2017-09-01

The Lattice Boltzmann Method (LBM) is a semi-microscopic method to simulate fluid mechanics by modelling distributions of particles moving and colliding on a lattice. We present 2-D simulations using the LBM of a fluid in a rectangular box being heated from below, and cooled from above, with a Rayleigh of Ra = 108, similar to current estimates of the Earth's mantle, and a Prandtl number of 5000. At this Prandtl number, the flow is found to be in the non-inertial regime where the inertial terms denoted I ≪ 1. Hence, the simulations presented lie within the regime of relevance for geodynamical problems. We obtain narrow upwelling plumes with mushroom heads and chutes of downwelling fluid as expected of a flow in the non-inertial regime. The method developed demonstrates that the LBM has great potential for simulating thermal convection and plume dynamics relevant to geodynamics, albeit with some limitations.

Towards Compatible and Interderivable Semantic Specifications for the Scheme Programming Language, Part I: Denotational Semantics, Natural Semantics, and Abstract Machines

DEFF Research Database (Denmark)

Danvy, Olivier

2008-01-01

We derive two big-step abstract machines, a natural semantics, and the valuation function of a denotational semantics based on the small-step abstract machine for Core Scheme presented by Clinger at PLDI'98. Starting from a functional implementation of this small-step abstract machine, (1) we fuse...... its transition function with its driver loop, obtaining the functional implementation of a big-step abstract machine; (2) we adjust this big-step abstract machine so that it is in defunctionalized form, obtaining the functional implementation of a second big-step abstract machine; (3) we...... refunctionalize this adjusted abstract machine, obtaining the functional implementation of a natural semantics in continuation style; and (4) we closure-unconvert this natural semantics, obtaining a compositional continuation-passing evaluation function which we identify as the functional implementation...

Flux-driven simulations of turbulence collapse

Energy Technology Data Exchange (ETDEWEB)

Park, G. Y.; Kim, S. S.; Jhang, Hogun; Rhee, T. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Diamond, P. H. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); CASS and Department of Physics, University of California, San Diego, La Jolla, California 92093-0429 (United States); Xu, X. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2015-03-15

Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.

Investigation of a Unified Chaotic System and Its Synchronization by Simulations

International Nuclear Information System (INIS)

Qing-Chu, Wu; Xin-Chu, Fu; Small, Michael

2010-01-01

We investigate a unified chaotic system and its synchronization including feedback synchronization and adaptive synchronization by numerical simulations. We propose a new dynamical quantity denoted by K, which connects adaptive synchronization and feedback synchronization, to analyze synchronization schemes. We find that K can estimate the smallest coupling strength for a unified chaotic system whether it is complete feedback or one-sided feedback. Based on the previous work, we also give a new dynamical method to compute the leading Lyapunov exponent. (general)

Numerical simulation of electromagnetic wave propagation using time domain meshless method

International Nuclear Information System (INIS)

Ikuno, Soichiro; Fujita, Yoshihisa; Itoh, Taku; Nakata, Susumu; Nakamura, Hiroaki; Kamitani, Atsushi

2012-01-01

The electromagnetic wave propagation in various shaped wave guide is simulated by using meshless time domain method (MTDM). Generally, Finite Differential Time Domain (FDTD) method is applied for electromagnetic wave propagation simulation. However, the numerical domain should be divided into rectangle meshes if FDTD method is applied for the simulation. On the other hand, the node disposition of MTDM can easily describe the structure of arbitrary shaped wave guide. This is the large advantage of the meshless time domain method. The results of computations show that the damping rate is stably calculated in case with R < 0.03, where R denotes a support radius of the weight function for the shape function. And the results indicate that the support radius R of the weight functions should be selected small, and monomials must be used for calculating the shape functions. (author)

Initial conditions for turbulent mixing simulations

Directory of Open Access Journals (Sweden)

T. Kaman

2010-01-01

Full Text Available In the context of the classical Rayleigh-Taylor hydrodynamical instability, we examine the much debated question of models for initial conditions and the possible influence of unrecorded long wave length contributions to the instability growth rate α.

Application of light-initiated explosive for simulating x-ray blowoff impulse effects on a full scale reentry vehicle

International Nuclear Information System (INIS)

Benham, R.A.; Mathews, F.H.; Higgins, P.B.

1976-01-01

Laboratory nuclear effects testing allows the study of reentry vehicle response to simulated exoatmospheric x-ray encounters. Light-initiated explosive produces the nearly simultaneous impulse loading of a structure by using a spray painted coating of explosive which is detonated by an intense flash of light. A lateral impulse test on a full scale reentry vehicle is described which demonstrates that the light-initiated explosive technique can be extended to the lateral loading of very large systems involving load discontinuities. This experiment required the development of a diagnostic method for verifying the applied impulse, and development of a large light source for simultaneously initiating the explosive over the surface of the vehicle. Acceptable comparison between measured strain response and code predictions is obtained. The structural capability and internal response of a vehicle subjected to an x-ray environment was determined from a light-initiated explosive test

Initial Study of An Effective Fast-Time Simulation Platform for Unmanned Aircraft System Traffic Management

Science.gov (United States)

Xue, Min; Rios, Joseph

2017-01-01

Small Unmanned Aerial Vehicles (sUAVs), typically 55 lbs and below, are envisioned to play a major role in surveilling critical assets, collecting important information, and delivering goods. Large scale small UAV operations are expected to happen in low altitude airspace in the near future. Many static and dynamic constraints exist in low altitude airspace because of manned aircraft or helicopter activities, various wind conditions, restricted airspace, terrain and man-made buildings, and conflict-avoidance among sUAVs. High sensitivity and high maneuverability are unique characteristics of sUAVs that bring challenges to effective system evaluations and mandate such a simulation platform different from existing simulations that were built for manned air traffic system and large unmanned fixed aircraft. NASA's Unmanned aircraft system Traffic Management (UTM) research initiative focuses on enabling safe and efficient sUAV operations in the future. In order to help define requirements and policies for a safe and efficient UTM system to accommodate a large amount of sUAV operations, it is necessary to develop a fast-time simulation platform that can effectively evaluate requirements, policies, and concepts in a close-to-reality environment. This work analyzed the impacts of some key factors including aforementioned sUAV's characteristics and demonstrated the importance of these factors in a successful UTM fast-time simulation platform.

Simulation of rod drop experiments in the initial cores of Loviisa and Mochovce

International Nuclear Information System (INIS)

Kaloinen, E.; Kyrki-Rajamaeki, R.; Wasastjerna, F.

1999-01-01

Interpretation of rod drop measurements during startup tests of the Loviisa reactors has earlier been studied with two-dimensional core calculations using a spatial prompt jump approximation. In these calculations the prediction for the reactivity meter reading was lower than the measured values by 25%. Another approach to solve the problem is simulation of the rod drop experiment with dynamic core calculations coupled with out of core calculations to estimate the response of ex-core ionization chambers for the reactivity meter. This report described the calculations performed with the three-dimensional dynamic code HEXTRAN for prediction of the reactivity meter readings in rod drop experiments in initial cores of the WWER-440 reactors. (Authors)

MAGI: many-component galaxy initializer

Science.gov (United States)

Miki, Yohei; Umemura, Masayuki

2018-04-01

Providing initial conditions is an essential procedure for numerical simulations of galaxies. The initial conditions for idealized individual galaxies in N-body simulations should resemble observed galaxies and be dynamically stable for time-scales much longer than their characteristic dynamical times. However, generating a galaxy model ab initio as a system in dynamical equilibrium is a difficult task, since a galaxy contains several components, including a bulge, disc, and halo. Moreover, it is desirable that the initial-condition generator be fast and easy to use. We have now developed an initial-condition generator for galactic N-body simulations that satisfies these requirements. The developed generator adopts a distribution-function-based method, and it supports various kinds of density models, including custom-tabulated inputs and the presence of more than one disc. We tested the dynamical stability of systems generated by our code, representing early- and late-type galaxies, with N = 2097 152 and 8388 608 particles, respectively, and we found that the model galaxies maintain their initial distributions for at least 1 Gyr. The execution times required to generate the two models were 8.5 and 221.7 seconds, respectively, which is negligible compared to typical execution times for N-body simulations. The code is provided as open-source software and is publicly and freely available at https://bitbucket.org/ymiki/magi.

Initial Self-Consistent 3D Electron-Cloud Simulations of the LHC Beam with the Code WARP+POSINST

International Nuclear Information System (INIS)

Vay, J; Furman, M A; Cohen, R H; Friedman, A; Grote, D P

2005-01-01

We present initial results for the self-consistent beam-cloud dynamics simulations for a sample LHC beam, using a newly developed set of modeling capability based on a merge [1] of the three-dimensional parallel Particle-In-Cell (PIC) accelerator code WARP [2] and the electron-cloud code POSINST [3]. Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST [3, 4

Precursor evolution and SCC initiation of cold-worked alloy 690 in simulated PWR primary water

Energy Technology Data Exchange (ETDEWEB)

Zhai, Ziqing; Kruska, Karen; Toloczko, Mychailo B.; Bruemmer, Stephen M.

2017-03-27

Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for the 21% and 31%CW CLT specimens loaded at their yield stress after ~9,220 h, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showed DCPD-indicated crack initiation after 10,400h exposure at constant stress intensity, which resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Interestingly, post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and will discuss their effects on crack initiation in CW alloy 690.

Evaluation of leadership skills during the simulation education course for the initial management of blunt trauma.

Science.gov (United States)

Schott, Eric; Brautigam, Robert T; Smola, Jacqueline; Burns, Karyl J

2012-04-01

Leadership skills of senior residents, trauma fellows, and a nurse practitioner were assessed during simulation training for the initial management of blunt trauma. This was a pilot, observational study, that in addition to skill development and assessment also sought to determine the need for a dedicated leadership training course for surgical residents. The study evaluated the leadership skills and adherence to Advance Trauma Life Support (ATLS) guidelines of the team leaders during simulation training. The team leaders' performances on criteria regarding prearrival planning, critical actions based on ATLS, injury identification, patient management, and communication were evaluated for each of five blunt-trauma scenarios. Although there was a statistically significant increase in leadership skills for performing ATLS critical actions, P skills for team leadership willbe a worthwhile endeavor at our institution.

Probabilistic Simulation of Multi-Scale Composite Behavior

Science.gov (United States)

Chamis, Christos C.

2012-01-01

A methodology is developed to computationally assess the non-deterministic composite response at all composite scales (from micro to structural) due to the uncertainties in the constituent (fiber and matrix) properties, in the fabrication process and in structural variables (primitive variables). The methodology is computationally efficient for simulating the probability distributions of composite behavior, such as material properties, laminate and structural responses. Bi-products of the methodology are probabilistic sensitivities of the composite primitive variables. The methodology has been implemented into the computer codes PICAN (Probabilistic Integrated Composite ANalyzer) and IPACS (Integrated Probabilistic Assessment of Composite Structures). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in composite typical laminates and comparing the results with the Monte Carlo simulation method. Available experimental data of composite laminate behavior at all scales fall within the scatters predicted by PICAN. Multi-scaling is extended to simulate probabilistic thermo-mechanical fatigue and to simulate the probabilistic design of a composite redome in order to illustrate its versatility. Results show that probabilistic fatigue can be simulated for different temperature amplitudes and for different cyclic stress magnitudes. Results also show that laminate configurations can be selected to increase the redome reliability by several orders of magnitude without increasing the laminate thickness--a unique feature of structural composites. The old reference denotes that nothing fundamental has been done since that time.

Initial Development of a Quadcopter Simulation Environment for Auralization

Science.gov (United States)

Christian, Andrew; Lawrence, Joseph

2016-01-01

This paper describes a recently created computer simulation of quadcopter flight dynamics for the NASA DELIVER project. The goal of this effort is to produce a simulation that includes a number of physical effects that are not usually found in other dynamics simulations (e.g., those used for flight controller development). These effects will be shown to have a significant impact on the fidelity of auralizations - entirely synthetic time-domain predictions of sound - based on this simulation when compared to a recording. High-fidelity auralizations are an important precursor to human subject tests that seek to understand the impact of vehicle configurations on noise and annoyance.

TRIB3 protein denotes a good prognosis in breast cancer patients and is associated with hypoxia sensitivity

International Nuclear Information System (INIS)

Wennemers, Marloes; Bussink, Johan; Grebenchtchikov, Nicolai; Sweep, Fred C.G.J.; Span, Paul N.

2011-01-01

Background: Tribbles homolog 3 (TRIB3) is a pseudokinase involved in the regulation of several signaling pathways involved in cell survival and/or cell stress. Here, we determined the correlation between breast cancer prognosis and TRIB3 protein levels and established the role of TRIB3 in cell survival after hypoxia and/or radiotherapy. Material and methods: TRIB3 mRNA and protein were quantified in a new independent breast cancer patient cohort using QPCR and a new specific avian antibody against TRIB3. In addition, we used siRNA-mediated knockdown of TRIB3 in a colony-forming assay after hypoxia and radiotherapy. Results: TRIB3 mRNA and protein levels did not correlate in breast cancer cell lines or human breast cancer material. We validated our earlier finding that high TRIB3 mRNA denotes a poor prognosis, but found that high TRIB3 protein levels were associated with a good prognosis in breast cancer patients. We also show that knockdown of TRIB3 resulted in an increased survival under hypoxic conditions. Conclusion: Whereas mRNA levels of TRIB3 are related with a poor prognosis, TRIB3 protein is associated with a good prognosis in human breast cancer patients, possibly due to the fact that TRIB3 is involved in hypoxia tolerance.

Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels

International Nuclear Information System (INIS)

Mente, Tobias

2015-01-01

Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

Simulating operator decision processes at SRL

International Nuclear Information System (INIS)

Hoecker, D.G.; Benhardt, H.C.; Pople, H.E. Jr.

1991-01-01

Cognitive environment simulation (CES) is both a methodology and an artificial intelligence (AI) tool. As a methodology, it denotes a technique that models human operators' cognitive processes to either (a) aid in designing the interface to a complex system (such as nuclear reactor control room) or (b) assess the cognitive causality that effects the likelihood of human error in specific accident scenarios. As an AI tool, CES is an expert system that models human intention formation and errors in a problem-solving context. The immediate objective of the reported work was to demonstrate the feasibility of applying CES to a new domain - that of the defense production reactors, whose design and operating philosophy differ in key areas from power reactors, where CES has already demonstrated interesting results

Molecular dynamics simulation of graphene growth at initial stage on Ni(100) facet for low flux C energy by CVD

Energy Technology Data Exchange (ETDEWEB)

Syuhada, Ibnu, E-mail: ibnu-syuhada-p3@yahoo.com; Rosikhin, Ahmad, E-mail: aulia-fikri-h@yahoo.co.id; Fikri, Aulia, E-mail: a.rosikhin86@yahoo.co.id; Noor, Fatimah A., E-mail: fatimah@fi.itb.ac.id; Winata, Toto, E-mail: toto@fi.itb.ac.id [Departement of Physics, Institute of Technology Bandung, Tamansari 64 Street, East Java (Indonesia)

2016-02-08

In this study, atomic simulation for graphene growth on Ni (100) at initial stage via chemical vapor deposition method has been developed. The C-C atoms interaction was performed by Terasoff potential mean while Ni-Ni interaction was specified by EAM (Embedded Atom Modified). On the other hand, we used very simple interatomic potential to describe Ni-C interaction during deposition process. From this simulation, it shows that the formation of graphene is not occurs through a combined deposition mechanism on Ni substrate but via C segregation. It means, Ni-C amorphous is source for graphene growth when cooling down of Ni substrate. This result is appropriate with experiments, tight binding and quantum mechanics simulation.

WRF Simulation over the Eastern Africa by use of Land Surface Initialization

Science.gov (United States)

Sakwa, V. N.; Case, J.; Limaye, A. S.; Zavodsky, B.; Kabuchanga, E. S.; Mungai, J.

2014-12-01

to quantify possible improvements in simulated temperature, moisture and precipitation resulting from the experimental land surface initialization. These MET tools enable KMS to monitor model forecast accuracy in near real time. This study highlights verification results of WRF runs over East Africa using the LIS land surface initialization.

Cardiogenic Shock: An Unusual Initial Presentation of Churg-Strauss Syndrome

Directory of Open Access Journals (Sweden)

M. Apirami

2018-01-01

Full Text Available Churg-Strauss syndrome (CSS is a rare autoimmune condition, characterized by necrotizing extravascular eosinophil rich granulomatous inflammation of the tissues and disseminated small-medium sized vessel vasculitis in a patient with bronchial asthma and tissue eosinophilia. Though pulmonary involvement is the predominant feature of CSS, extra pulmonary involvement, in particular, cardiac involvement, denotes an adverse outcome. Here we report a 50-year-old female who presented with cardiogenic shock due to an acute coronary event as the initial manifestation of CSS. A subsequent coronary angiogram revealed normal epicardial coronaries. She was a patient with bronchial asthma and developed vasculitic rash, bilateral sensory motor polyneuropathy, and migratory peripheral lung field shadows in the background of peripheral eosinophilia during the course of the illness. She was diagnosed as having CSS based on ACR criteria and aggressively treated with immunosuppressants according to her Five-Factor Score and has shown prompt response to therapy. This case report adds to the literature another rare initial presentation of CSS to the existing array of its clinical manifestations.

SIMULA - C a simplified PC simulation training fool developed for the initial training of NPP operations personnel

International Nuclear Information System (INIS)

Reuhl, R.

1997-01-01

During initial training of some 50 young reactor operators and shift supervisors in the last 5 years in Biblis it was found that it takes some time before trainees gain a food overview of the most important plant systems and develop a ''feeling'' of the dynamic plant behaviour which is an important prerequisite for the first full-scope simulator training courses. To enhance this, a PC software training tool was developed SIMULA - C. (author)

Simulation study of the initial crystallization processes of poly(3-hexylthiophene) in solution: ordering dynamics of main chains and side chains.

Science.gov (United States)

Takizawa, Yuumi; Shimomura, Takeshi; Miura, Toshiaki

2013-05-23

We study the initial nucleation dynamics of poly(3-hexylthiophene) (P3HT) in solution, focusing on the relationship between the ordering process of main chains and that of side chains. We carried out Langevin dynamics simulation and found that the initial nucleation processes consist of three steps: the ordering of ring orientation, the ordering of main-chain vectors, and the ordering of side chains. At the start, the normal vectors of thiophene rings aligned in a very short time, followed by alignment of main-chain end-to-end vectors. The flexible side-chain ordering took almost 5 times longer than the rigid-main-chain ordering. The simulation results indicated that the ordering of side chains was induced after the formation of the regular stack structure of main chains. This slow ordering dynamics of flexible side chains is one of the factors that cause anisotropic nuclei growth, which would be closely related to the formation of nanofiber structures without external flow field. Our simulation results revealed how the combined structure of the planar and rigid-main-chain backbones and the sparse flexible side chains lead to specific ordering behaviors that are not observed in ordinary linear polymer crystallization processes.

Use of Simulation in Nursing Education: Initial Experiences on a European Union Lifelong Learning Programme--Leonardo Da Vinci Project

Science.gov (United States)

Terzioglu, Fusun; Tuna, Zahide; Duygulu, Sergul; Boztepe, Handan; Kapucu, Sevgisun; Ozdemir, Leyla; Akdemir, Nuran; Kocoglu, Deniz; Alinier, Guillaume; Festini, Filippo

2013-01-01

Aim: The aim of this paper is to share the initial experiences on a European Union (EU) Lifelong Learning Programme Leonardo Da Vinci Transfer of Innovation Project related to the use of simulation-based learning with nursing students from Turkey. The project started at the end of the 2010 involving 7 partners from 3 different countries including…

Low-cost autonomous orbit control about Mars: Initial simulation results

Science.gov (United States)

Dawson, S. D.; Early, L. W.; Potterveld, C. W.; Königsmann, H. J.

1999-11-01

Interest in studying the possibility of extraterrestrial life has led to the re-emergence of the Red Planet as a major target of planetary exploration. Currently proposed missions in the post-2000 period are routinely calling for rendezvous with ascent craft, long-term orbiting of, and sample-return from Mars. Such missions would benefit greatly from autonomous orbit control as a means to reduce operations costs and enable contact with Mars ground stations out of view of the Earth. This paper present results from initial simulations of autonomously controlled orbits around Mars, and points out possible uses of the technology and areas of routine Mars operations where such cost-conscious and robust autonomy could prove most effective. These simulations have validated the approach and control philosophies used in the development of this autonomous orbit controller. Future work will refine the controller, accounting for systematic and random errors in the navigation of the spacecraft from the sensor suite, and will produce prototype flight code for inclusion on future missions. A modified version of Microcosm's commercially available High Precision Orbit Propagator (HPOP) was used in the preparation of these results due to its high accuracy and speed of operation. Control laws were developed to allow an autonomously controlled spacecraft to continuously control to a pre-defined orbit about Mars with near-optimal propellant usage. The control laws were implemented as an adjunct to HPOP. The GSFC-produced 50 × 50 field model of the Martian gravitational potential was used in all simulations. The Martian atmospheric drag was modeled using an exponentially decaying atmosphere based on data from the Mars-GRAM NASA Ames model. It is hoped that the simple atmosphere model that was implemented can be significantly improved in the future so as to approach the fidelity of the Mars-GRAM model in its predictions of atmospheric density at orbital altitudes. Such additional work

Evaluating the Credibility of Transport Processes in Simulations of Ozone Recovery using the Global Modeling Initiative Three-dimensional Model

Science.gov (United States)

Strahan, Susan E.; Douglass, Anne R.

2004-01-01

The Global Modeling Initiative (GMI) has integrated two 36-year simulations of an ozone recovery scenario with an offline chemistry and tra nsport model using two different meteorological inputs. Physically ba sed diagnostics, derived from satellite and aircraft data sets, are d escribed and then used to evaluate the realism of temperature and transport processes in the simulations. Processes evaluated include barri er formation in the subtropics and polar regions, and extratropical w ave-driven transport. Some diagnostics are especially relevant to sim ulation of lower stratospheric ozone, but most are applicable to any stratospheric simulation. The global temperature evaluation, which is relevant to gas phase chemical reactions, showed that both sets of me teorological fields have near climatological values at all latitudes and seasons at 30 hPa and below. Both simulations showed weakness in upper stratospheric wave driving. The simulation using input from a g eneral circulation model (GMI(GCM)) showed a very good residual circulation in the tropics and Northern Hemisphere. The simulation with inp ut from a data assimilation system (GMI(DAS)) performed better in the midlatitudes than it did at high latitudes. Neither simulation forms a realistic barrier at the vortex edge, leading to uncertainty in the fate of ozone-depleted vortex air. Overall, tracer transport in the offline GML(GCM) has greater fidelity throughout the stratosphere tha n it does in the GMI(DAS)

Development and initial validation of a novel smoothed-particle hydrodynamics-based simulation model of trabecular bone penetration by metallic implants.

Science.gov (United States)

Kulper, Sloan A; Fang, Christian X; Ren, Xiaodan; Guo, Margaret; Sze, Kam Y; Leung, Frankie K L; Lu, William W

2018-04-01

A novel computational model of implant migration in trabecular bone was developed using smoothed-particle hydrodynamics (SPH), and an initial validation was performed via correlation with experimental data. Six fresh-frozen human cadaveric specimens measuring 10 × 10 × 20 mm were extracted from the proximal femurs of female donors (mean age of 82 years, range 75-90, BV/TV ratios between 17.88% and 30.49%). These specimens were then penetrated under axial loading to a depth of 10 mm with 5 mm diameter cylindrical indenters bearing either flat or sharp/conical tip designs similar to blunt and self-tapping cancellous screws, assigned in a random manner. SPH models were constructed based on microCT scans (17.33 µm) of the cadaveric specimens. Two initial specimens were used for calibration of material model parameters. The remaining four specimens were then simulated in silico using identical material model parameters. Peak forces varied between 92.0 and 365.0 N in the experiments, and 115.5-352.2 N in the SPH simulations. The concordance correlation coefficient between experimental and simulated pairs was 0.888, with a 95%CI of 0.8832-0.8926, a Pearson ρ (precision) value of 0.9396, and a bias correction factor Cb (accuracy) value of 0.945. Patterns of bone compaction were qualitatively similar; both experimental and simulated flat-tipped indenters produced dense regions of compacted material adjacent to the advancing face of the indenter, while sharp-tipped indenters deposited compacted material along their peripheries. Simulations based on SPH can produce accurate predictions of trabecular bone penetration that are useful for characterizing implant performance under high-strain loading conditions. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1114-1123, 2018. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Environmental fate and transport of chemical signatures from buried landmines -- Screening model formulation and initial simulations

Energy Technology Data Exchange (ETDEWEB)

Phelan, J.M.; Webb, S.W.

1997-06-01

The fate and transport of chemical signature molecules that emanate from buried landmines is strongly influenced by physical chemical properties and by environmental conditions of the specific chemical compounds. Published data have been evaluated as the input parameters that are used in the simulation of the fate and transport processes. A one-dimensional model developed for screening agricultural pesticides was modified and used to simulate the appearance of a surface flux above a buried landmine, estimate the subsurface total concentration, and show the phase specific concentrations at the ground surface. The physical chemical properties of TNT cause a majority of the mass released to the soil system to be bound to the solid phase soil particles. The majority of the transport occurs in the liquid phase with diffusion and evaporation driven advection of soil water as the primary mechanisms for the flux to the ground surface. The simulations provided herein should only be used for initial conceptual designs of chemical pre-concentration subsystems or complete detection systems. The physical processes modeled required necessary simplifying assumptions to allow for analytical solutions. Emerging numerical simulation tools will soon be available that should provide more realistic estimates that can be used to predict the success of landmine chemical detection surveys based on knowledge of the chemical and soil properties, and environmental conditions where the mines are buried. Additional measurements of the chemical properties in soils are also needed before a fully predictive approach can be confidently applied.

A new equilibrium torus solution and GRMHD initial conditions

Science.gov (United States)

Penna, Robert F.; Kulkarni, Akshay; Narayan, Ramesh

2013-11-01

Context. General relativistic magnetohydrodynamic (GRMHD) simulations are providing influential models for black hole spin measurements, gamma ray bursts, and supermassive black hole feedback. Many of these simulations use the same initial condition: a rotating torus of fluid in hydrostatic equilibrium. A persistent concern is that simulation results sometimes depend on arbitrary features of the initial torus. For example, the Bernoulli parameter (which is related to outflows), appears to be controlled by the Bernoulli parameter of the initial torus. Aims: In this paper, we give a new equilibrium torus solution and describe two applications for the future. First, it can be used as a more physical initial condition for GRMHD simulations than earlier torus solutions. Second, it can be used in conjunction with earlier torus solutions to isolate the simulation results that depend on initial conditions. Methods: We assume axisymmetry, an ideal gas equation of state, constant entropy, and ignore self-gravity. We fix an angular momentum distribution and solve the relativistic Euler equations in the Kerr metric. Results: The Bernoulli parameter, rotation rate, and geometrical thickness of the torus can be adjusted independently. Our torus tends to be more bound and have a larger radial extent than earlier torus solutions. Conclusions: While this paper was in preparation, several GRMHD simulations appeared based on our equilibrium torus. We believe it will continue to provide a more realistic starting point for future simulations.

2003 Initial Assessments of Closure for the C Tank Farm Field Investigation Report (FIR):Numerical Simulations

International Nuclear Information System (INIS)

Zhang, Z F.; Freedman, Vicky L.; White, Mark D.

2003-01-01

In support of CH2M HILL Hanford Group, Inc.'s (CHG) preparation of a Field Investigative Report (FIR) for the closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, a set of numerical simulations of flow and solute transport was executed to predict the performance of surface barriers for reducing long-term risks from potential groundwater contamination at the C Farm WMA. This report documents the simulation of 14 cases (and two verification cases) involving two-dimensional cross sections through the C Farm WMA tanks C-103 - C-112. Utilizing a unit release scenario at Tank C-112, four different types of leaks were simulated. These simulations assessed the impact of leakage during retrieval, past leaks, and tank residual wastes and tank ancillary equipment following closure activities. . Two transported solutes were considered: uranium-238 (U-238) and technetium-99 (Tc-99). To evaluate the impact of sorption to the subsurface materials, six different retardation coefficients were simulated for U-238. Overall, simulations results for the C Farm WMA showed that only a small fraction of the U-238 with retardation factors greater than 0.6 migrated from the vadose zone in all of the cases. For the conservative solute, Tc-99, results showed that the simulations investigating leakages during retrieval demonstrated the highest WMA peak concentrations and the earliest arrival times due to the high infiltration rate before the use of surface barriers and the addition of water into the system. Simulations investigating past leaks showed similar peaks and arrival times as the retrieval leak cases. Several different release rates were used to investigate contaminant transport from residual tank wastes. All showed similar peak concentrations and arrival times, except for the lowest initial release rate, which was 1,000 times slower than the highest release rate. Past leaks were also investigated with different release rate models, including

OpenGeoSys: An open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

DEFF Research Database (Denmark)

Kolditz, O.; Bauer, S.; Bilke, L.

In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical processes in porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM...

Using Collaborative Simulation Modeling to Develop a Web-Based Tool to Support Policy-Level Decision Making About Breast Cancer Screening Initiation Age

Directory of Open Access Journals (Sweden)

Elizabeth S. Burnside MD, MPH, MS

2017-07-01

Full Text Available Background: There are no publicly available tools designed specifically to assist policy makers to make informed decisions about the optimal ages of breast cancer screening initiation for different populations of US women. Objective: To use three established simulation models to develop a web-based tool called Mammo OUTPuT. Methods: The simulation models use the 1970 US birth cohort and common parameters for incidence, digital screening performance, and treatment effects. Outcomes include breast cancers diagnosed, breast cancer deaths averted, breast cancer mortality reduction, false-positive mammograms, benign biopsies, and overdiagnosis. The Mammo OUTPuT tool displays these outcomes for combinations of age at screening initiation (every year from 40 to 49, annual versus biennial interval, lifetime versus 10-year horizon, and breast density, compared to waiting to start biennial screening at age 50 and continuing to 74. The tool was piloted by decision makers (n = 16 who completed surveys. Results: The tool demonstrates that benefits in the 40s increase linearly with earlier initiation age, without a specific threshold age. Likewise, the harms of screening increase monotonically with earlier ages of initiation in the 40s. The tool also shows users how the balance of benefits and harms varies with breast density. Surveys revealed that 100% of users (16/16 liked the appearance of the site; 94% (15/16 found the tool helpful; and 94% (15/16 would recommend the tool to a colleague. Conclusions: This tool synthesizes a representative subset of the most current CISNET (Cancer Intervention and Surveillance Modeling Network simulation model outcomes to provide policy makers with quantitative data on the benefits and harms of screening women in the 40s. Ultimate decisions will depend on program goals, the population served, and informed judgments about the weight of benefits and harms.

Simulation of Evacuated Tube Collector and Storage of Hybrid Air-conditioning System

Directory of Open Access Journals (Sweden)

Mustafa Ahmed Abdulhussain

2018-02-01

Full Text Available The CFD transient simulation of superheating the refrigerant R410 through the heat exchange with the evacuated tube water heating system of the hybrid split air conditioner that is subjected to solar radiation of constant intensity with the contribution of fan accelerated air is performed by the ANSYS-CFX code. The comparison with experimental work showed a minimum percentage error 8% of the predicted refrigerant evaporative heat transfer with storage tank horizontal tubing. In addition, the results denoted high absorption rate for the evacuated tubes, reducing highly reversed heat transmission for the circulated water. 

Investigation of the SCS-CN initial abstraction ratio using a Monte Carlo simulation for the derived flood frequency curves

Science.gov (United States)

Caporali, E.; Chiarello, V.; Galeati, G.

2014-12-01

Peak discharges estimates for a given return period are of primary importance in engineering practice for risk assessment and hydraulic structure design. Different statistical methods are chosen here for the assessment of flood frequency curve: one indirect technique based on the extreme rainfall event analysis, the Peak Over Threshold (POT) model and the Annual Maxima approach as direct techniques using river discharge data. In the framework of the indirect method, a Monte Carlo simulation approach is adopted to determine a derived frequency distribution of peak runoff using a probabilistic formulation of the SCS-CN method as stochastic rainfall-runoff model. A Monte Carlo simulation is used to generate a sample of different runoff events from different stochastic combination of rainfall depth, storm duration, and initial loss inputs. The distribution of the rainfall storm events is assumed to follow the GP law whose parameters are estimated through GEV's parameters of annual maximum data. The evaluation of the initial abstraction ratio is investigated since it is one of the most questionable assumption in the SCS-CN model and plays a key role in river basin characterized by high-permeability soils, mainly governed by infiltration excess mechanism. In order to take into account the uncertainty of the model parameters, this modified approach, that is able to revise and re-evaluate the original value of the initial abstraction ratio, is implemented. In the POT model the choice of the threshold has been an essential issue, mainly based on a compromise between bias and variance. The Generalized Extreme Value (GEV) distribution fitted to the annual maxima discharges is therefore compared with the Pareto distributed peaks to check the suitability of the frequency of occurrence representation. The methodology is applied to a large dam in the Serchio river basin, located in the Tuscany Region. The application has shown as Monte Carlo simulation technique can be a useful

Generation of initial geometries for the simulation of the physical system in the DualPHYsics code; Generacion de geometrias iniciales para la simulacion del sistema fisico en el codigo DualSPHysics

Energy Technology Data Exchange (ETDEWEB)

Segura Q, E.

2013-07-01

In the diverse research areas of the Instituto Nacional de Investigaciones Nucleares (ININ) are different activities related to science and technology, one of great interest is the study and treatment of the collection and storage of radioactive waste. Therefore at ININ the draft on the simulation of the pollutants diffusion in the soil through a porous medium (third stage) has this problem inherent aspects, hence a need for such a situation is to generate the initial geometry of the physical system For the realization of the simulation method is implemented smoothed particle hydrodynamics (SPH). This method runs in DualSPHysics code, which has great versatility and ability to simulate phenomena of any physical system where hydrodynamic aspects combine. In order to simulate a physical system DualSPHysics code, you need to preset the initial geometry of the system of interest, then this is included in the input file of the code. The simulation sets the initial geometry through regular geometric bodies positioned at different points in space. This was done through a programming language (Fortran, C + +, Java, etc..). This methodology will provide the basis to simulate more complex geometries future positions and form. (Author)

Voltage equilibration for reactive atomistic simulations of electrochemical processes

International Nuclear Information System (INIS)

Onofrio, Nicolas; Strachan, Alejandro

2015-01-01

We introduce electrochemical dynamics with implicit degrees of freedom (EChemDID), a model to describe electrochemical driving force in reactive molecular dynamics simulations. The method describes the equilibration of external electrochemical potentials (voltage) within metallic structures and their effect on the self-consistent partial atomic charges used in reactive molecular dynamics. An additional variable assigned to each atom denotes the local potential in its vicinity and we use fictitious, but computationally convenient, dynamics to describe its equilibration within connected metallic structures on-the-fly during the molecular dynamics simulation. This local electrostatic potential is used to dynamically modify the atomic electronegativities used to compute partial atomic changes via charge equilibration. Validation tests show that the method provides an accurate description of the electric fields generated by the applied voltage and the driving force for electrochemical reactions. We demonstrate EChemDID via simulations of the operation of electrochemical metallization cells. The simulations predict the switching of the device between a high-resistance to a low-resistance state as a conductive metallic bridge is formed and resistive currents that can be compared with experimental measurements. In addition to applications in nanoelectronics, EChemDID could be useful to model electrochemical energy conversion devices

WE-DE-202-01: Connecting Nanoscale Physics to Initial DNA Damage Through Track Structure Simulations

Energy Technology Data Exchange (ETDEWEB)

Schuemann, J. [Massachusetts General Hospital (United States)

2016-06-15

Radiation therapy for the treatment of cancer has been established as a highly precise and effective way to eradicate a localized region of diseased tissue. To achieve further significant gains in the therapeutic ratio, we need to move towards biologically optimized treatment planning. To achieve this goal, we need to understand how the radiation-type dependent patterns of induced energy depositions within the cell (physics) connect via molecular, cellular and tissue reactions to treatment outcome such as tumor control and undesirable effects on normal tissue. Several computational biology approaches have been developed connecting physics to biology. Monte Carlo simulations are the most accurate method to calculate physical dose distributions at the nanometer scale, however simulations at the DNA scale are slow and repair processes are generally not simulated. Alternative models that rely on the random formation of individual DNA lesions within one or two turns of the DNA have been shown to reproduce the clusters of DNA lesions, including single strand breaks (SSBs), double strand breaks (DSBs) without the need for detailed track structure simulations. Efficient computational simulations of initial DNA damage induction facilitate computational modeling of DNA repair and other molecular and cellular processes. Mechanistic, multiscale models provide a useful conceptual framework to test biological hypotheses and help connect fundamental information about track structure and dosimetry at the sub-cellular level to dose-response effects on larger scales. In this symposium we will learn about the current state of the art of computational approaches estimating radiation damage at the cellular and sub-cellular scale. How can understanding the physics interactions at the DNA level be used to predict biological outcome? We will discuss if and how such calculations are relevant to advance our understanding of radiation damage and its repair, or, if the underlying biological

WE-DE-202-01: Connecting Nanoscale Physics to Initial DNA Damage Through Track Structure Simulations

International Nuclear Information System (INIS)

Schuemann, J.

2016-01-01

Radiation therapy for the treatment of cancer has been established as a highly precise and effective way to eradicate a localized region of diseased tissue. To achieve further significant gains in the therapeutic ratio, we need to move towards biologically optimized treatment planning. To achieve this goal, we need to understand how the radiation-type dependent patterns of induced energy depositions within the cell (physics) connect via molecular, cellular and tissue reactions to treatment outcome such as tumor control and undesirable effects on normal tissue. Several computational biology approaches have been developed connecting physics to biology. Monte Carlo simulations are the most accurate method to calculate physical dose distributions at the nanometer scale, however simulations at the DNA scale are slow and repair processes are generally not simulated. Alternative models that rely on the random formation of individual DNA lesions within one or two turns of the DNA have been shown to reproduce the clusters of DNA lesions, including single strand breaks (SSBs), double strand breaks (DSBs) without the need for detailed track structure simulations. Efficient computational simulations of initial DNA damage induction facilitate computational modeling of DNA repair and other molecular and cellular processes. Mechanistic, multiscale models provide a useful conceptual framework to test biological hypotheses and help connect fundamental information about track structure and dosimetry at the sub-cellular level to dose-response effects on larger scales. In this symposium we will learn about the current state of the art of computational approaches estimating radiation damage at the cellular and sub-cellular scale. How can understanding the physics interactions at the DNA level be used to predict biological outcome? We will discuss if and how such calculations are relevant to advance our understanding of radiation damage and its repair, or, if the underlying biological

Simulation and verification studies of reactivity initiated accident by comparative approach of NK/TH coupling codes and RELAP5 code

Energy Technology Data Exchange (ETDEWEB)

Ud-Din Khan, Salah [Chinese Academy of Sciences, Hefei (China). Inst. of Plasma Physics; King Saud Univ., Riyadh (Saudi Arabia). Sustainable Energy Technologies Center; Peng, Minjun [Harbin Engineering Univ. (China). College of Nuclear Science and Technology; Yuntao, Song; Ud-Din Khan, Shahab [Chinese Academy of Sciences, Hefei (China). Inst. of Plasma Physics; Haider, Sajjad [King Saud Univ., Riyadh (Saudi Arabia). Sustainable Energy Technologies Center

2017-02-15

The objective is to analyze the safety of small modular nuclear reactors of 220 MWe power. Reactivity initiated accidents (RIA) were investigated by neutron kinetic/thermal hydraulic (NK/TH) coupling approach and thermal hydraulic code i.e., RELAP5. The results obtained by these approaches were compared for validation and accuracy of simulation. In the NK/TH coupling technique, three codes (HELIOS, REMARK, THEATRe) were used. These codes calculate different parameters of the reactor core (fission power, reactivity, fuel temperature and inlet/outlet temperatures). The data exchanges between the codes were assessed by running the codes simultaneously. The results obtained from both (NK/TH coupling) and RELAP5 code analyses complement each other, hence confirming the accuracy of simulation.

Fundamental study of crack initiation and propagation

International Nuclear Information System (INIS)

Norris, D.M. Jr.; Reaugh, J.E.; Moran, B.; Quinones, D.F.; Wilkins, M.L.

1977-01-01

Objective is to determine the fracture toughness of A533B-1 steel by computer modeling Charpy V-notch tests. A computer model of ductile fracture was developed that predicts fracture initiation. The model contains a set of material-dependent parameters obtained by computer simulations of small specimen tests. The computer calculations give detailed stress and strain histories up to the time of fracture, which are used to determine the model parameter values. The calibrated fracture model, that correctly predicts fracture initiation (and initiation energy) in the Charpy specimen, may then be used to simulate tests of accepted fracture-toughness specimens and hence obtain fracture toughness. The model parameters were calibrated to predict fracture in four different test specimens: two different notched-tension specimens, a simple tension specimen, and a precracked compact-tension specimen. The model was then used in a computer simulation of the Charpy V-notch specimen to initiate and advance a flat fracture. Results were compared with interrupted Charpy tests. Calibration of the model for two additional heat treatments of A533B-1 steel is in progress

An Innovative Tool for Intraoperative Electron Beam Radiotherapy Simulation and Planning: Description and Initial Evaluation by Radiation Oncologists

Energy Technology Data Exchange (ETDEWEB)

Pascau, Javier, E-mail: jpascau@mce.hggm.es [Unidad de Medicina y Cirugia Experimental, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Departamento de Bioingenieria e Ingenieria Aeroespacial, Universidad Carlos III de Madrid, Madrid (Spain); Santos Miranda, Juan Antonio [Servicio de Oncologia Radioterapica, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Facultad de Medicina, Universidad Complutense de Madrid, Madrid (Spain); Calvo, Felipe A. [Servicio de Oncologia Radioterapica, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Facultad de Medicina, Universidad Complutense de Madrid, Madrid (Spain); Departamento de Oncologia, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Bouche, Ana; Morillo, Virgina [Consorcio Hospitalario Provincial de Castellon, Castellon (Spain); Gonzalez-San Segundo, Carmen [Servicio de Oncologia Radioterapica, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Facultad de Medicina, Universidad Complutense de Madrid, Madrid (Spain); Ferrer, Carlos; Lopez Tarjuelo, Juan [Consorcio Hospitalario Provincial de Castellon, Castellon (Spain); and others

2012-06-01

Purpose: Intraoperative electron beam radiation therapy (IOERT) involves a modified strategy of conventional radiation therapy and surgery. The lack of specific planning tools limits the spread of this technique. The purpose of the present study is to describe a new simulation and planning tool and its initial evaluation by clinical users. Methods and Materials: The tool works on a preoperative computed tomography scan. A physician contours regions to be treated and protected and simulates applicator positioning, calculating isodoses and the corresponding dose-volume histograms depending on the selected electron energy. Three radiation oncologists evaluated data from 15 IOERT patients, including different tumor locations. Segmentation masks, applicator positions, and treatment parameters were compared. Results: High parameter agreement was found in the following cases: three breast and three rectal cancer, retroperitoneal sarcoma, and rectal and ovary monotopic recurrences. All radiation oncologists performed similar segmentations of tumors and high-risk areas. The average applicator position difference was 1.2 {+-} 0.95 cm. The remaining cancer sites showed higher deviations because of differences in the criteria for segmenting high-risk areas (one rectal, one pancreas) and different surgical access simulated (two rectal, one Ewing sarcoma). Conclusions: The results show that this new tool can be used to simulate IOERT cases involving different anatomic locations, and that preplanning has to be carried out with specialized surgical input.

Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels; Numerische Simulation der wasserstoffunterstuetzten Rissbildung in austentisch-ferritischen Duplexstaehlen

Energy Technology Data Exchange (ETDEWEB)

Mente, Tobias

2015-07-01

Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

Quantification of the interception and initial retention of radioactive contaminants deposited on pasture grass by simulated rain

International Nuclear Information System (INIS)

Hoffman, F.O.; Thiessen, K.M.; Frank, M.L.; Blaylock, B.G.

1992-01-01

Simulated rain containing both soluble radionuclides and insoluble particles labeled with radionuclides was applied to pasture-type vegetation under conditions similar to those found during convective storms. The fraction of material in rain intercepted by vegetation and initially retained was determined for three sizes of insoluble polystyrene microspheres, soluble 7 Be 2+ and soluble 131 I as periodate or iodide, over a range of rainfall amounts of both moderate- and high-intensity precipitation. Values for the interception and initial retention by vegetation (interception fractions) for soluble forms of 131 I in simulated rain are much less than those for insoluble particles and the reactive cation 7 Be 2+ . The interception fraction for soluble 131 I is an inverse function of rain amount. The mass interception factor (the interception fraction normalized for biomass) of 131 I is almost solely dependent on the amount of rain. The 131 I vegetation-to-rain concentration ratio is relatively constant at approximately 2.6 ι kg -1 . For 7 Be 2+ and the insoluble particles, the interception fractions range from 0.1 to 0.6 with geometric means of approximately 0.3. For these materials there is a greater dependence on biomass than on rain amount; the geometric means of the mass interception factors for these substances range from 0.99 to 2.4 m 2 kg -1 . These results indicate that anionic 131 I is essentially removed with the water once the vegetation surface becomes saturated and that the 7 Be cation and the insoluble particles are adsorbed to or settle out on the plant surface. (Author)

Sensitivity of a Simulated Derecho Event to Model Initial Conditions

Science.gov (United States)

Wang, Wei

2014-05-01

Since 2003, the MMM division at NCAR has been experimenting cloud-permitting scale weather forecasting using Weather Research and Forecasting (WRF) model. Over the years, we've tested different model physics, and tried different initial and boundary conditions. Not surprisingly, we found that the model's forecasts are more sensitive to the initial conditions than model physics. In 2012 real-time experiment, WRF-DART (Data Assimilation Research Testbed) at 15 km was employed to produce initial conditions for twice-a-day forecast at 3 km. On June 29, this forecast system captured one of the most destructive derecho event on record. In this presentation, we will examine forecast sensitivity to different model initial conditions, and try to understand the important features that may contribute to the success of the forecast.

Virtual reality in urban water management: communicating urban flooding with particle-based CFD simulations.

Science.gov (United States)

Winkler, Daniel; Zischg, Jonatan; Rauch, Wolfgang

2018-01-01

For communicating urban flood risk to authorities and the public, a realistic three-dimensional visual display is frequently more suitable than detailed flood maps. Virtual reality could also serve to plan short-term flooding interventions. We introduce here an alternative approach for simulating three-dimensional flooding dynamics in large- and small-scale urban scenes by reaching out to computer graphics. This approach, denoted 'particle in cell', is a particle-based CFD method that is used to predict physically plausible results instead of accurate flow dynamics. We exemplify the approach for the real flooding event in July 2016 in Innsbruck.

Lightning initiation mechanism based on the development of relativistic runaway electron avalanches triggered by background cosmic radiation: Numerical simulation

International Nuclear Information System (INIS)

Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.

2011-01-01

The mechanism of lightning initiation due to electric field enhancement by the polarization of a conducting channel produced by relativistic runaway electron avalanches triggered by background cosmic radiation has been simulated numerically. It is shown that the fields at which the start of a lightning leader is possible even in the absence of precipitations are locally realized for realistic thundercloud configurations and charges. The computational results agree with the in-situ observations of penetrating radiation enhancement in thunderclouds.

Lightning initiation mechanism based on the development of relativistic runaway electron avalanches triggered by background cosmic radiation: Numerical simulation

Energy Technology Data Exchange (ETDEWEB)

Babich, L. P., E-mail: babich@elph.vniief.ru; Bochkov, E. I.; Kutsyk, I. M. [All-Russian Research Institute of Experimental Physics, Russian Federal Nuclear Center (Russian Federation)

2011-05-15

The mechanism of lightning initiation due to electric field enhancement by the polarization of a conducting channel produced by relativistic runaway electron avalanches triggered by background cosmic radiation has been simulated numerically. It is shown that the fields at which the start of a lightning leader is possible even in the absence of precipitations are locally realized for realistic thundercloud configurations and charges. The computational results agree with the in-situ observations of penetrating radiation enhancement in thunderclouds.

Investigation of roughing machining simulation by using visual basic programming in NX CAM system

Science.gov (United States)

Hafiz Mohamad, Mohamad; Nafis Osman Zahid, Muhammed

2018-03-01

This paper outlines a simulation study to investigate the characteristic of roughing machining simulation in 4th axis milling processes by utilizing visual basic programming in NX CAM systems. The selection and optimization of cutting orientation in rough milling operation is critical in 4th axis machining. The main purpose of roughing operation is to approximately shape the machined parts into finished form by removing the bulk of material from workpieces. In this paper, the simulations are executed by manipulating a set of different cutting orientation to generate estimated volume removed from the machine parts. The cutting orientation with high volume removal is denoted as an optimum value and chosen to execute a roughing operation. In order to run the simulation, customized software is developed to assist the routines. Operations build-up instructions in NX CAM interface are translated into programming codes via advanced tool available in the Visual Basic Studio. The codes is customized and equipped with decision making tools to run and control the simulations. It permits the integration with any independent program files to execute specific operations. This paper aims to discuss about the simulation program and identifies optimum cutting orientations for roughing processes. The output of this study will broaden up the simulation routines performed in NX CAM systems.

Examining the effects of microstructure and loading on the shock initiation of HMX with mesoscale simulations

Science.gov (United States)

Springer, H. Keo; Tarver, Craig; Bastea, Sorin

2015-06-01

We perform reactive mesoscale simulations to study shock initiation in HMX over a range of pore morphologies and sizes, porosities, and loading conditions in order to improve our understanding of structure-performance relationships. These relationships are important because they guide the development of advanced macroscale models incorporating hot spot mechanisms and the optimization of novel energetic material microstructures. Mesoscale simulations are performed using the multiphysics hydrocode, ALE3D. Spherical, elliptical, polygonal, and crack-like pore geometries 0.1, 1, 10, and 100 microns in size and 2, 5, 10, and 14% porosity are explored. Loading conditions are realized with shock pressures of 6, 10, 20, 38, and 50 GPa. A Cheetah-based tabular model, including temperature-dependent heat capacity, is used for the unreacted and the product equation-of-state. Also, in-line Cheetah is used to probe chemical species evolution. The influence of microstructure and shock loading on shock-to-detonation-transition run distance, reaction rate and product gas species evolution are discussed. This work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. This work is funded by the Joint DoD-DOE Munitions Program.

Sandbox Simulations of the Evolution of a Subduction Wedge following Subduction Initiation

Science.gov (United States)

Brandon, M. T.; Ma, K. F.; DeWolf, W.

2012-12-01

Subduction wedges at accreting subduction zones are bounded by a landward dipping pro-shear zone (= subduction thrust) and a seaward-dipping retro-shear zone in the overriding plate. For the Cascadia subduction zone, the surface trace of the retro-shear zone corresponds to the east side of the Coast Ranges of Oregon and Washington and the Insular Mountains of Vancouver Island. This coastal high or forearc high shows clear evidence of long-term uplift and erosion along its entire length, indicating that it is an active part of the Cascadia subduction wedge. The question addressed here is what controls the location of the retro-shear zone? In the popular double-sided wedge model of Willet et al (Geology 1993), the retro-shear zone remains pinned to the S point, which is interpreted to represent where the upper-plate Moho intersects the subduction zone. For this interpretation, the relatively strong mantle is considered to operate as a flat backstop. That model, however. is somewhat artificial in that the two plates collide in a symmetric fashion with equal crustal thicknesses on both sides. Using sandbox experiments, we explore a more realistic configuration where the upper and lower plate are separated by a gentle dipping (10 degree) pro-shear zone, to simulate the initial asymmetric geometry of the subduction thrust immediately after initiation of subduction. The entire lithosphere must fail along some plane for subduction to begin and this failure plane must dip in the direction of subduction. Thus, the initial geometry of the overriding plate is better approximated as a tapered wedge than as a layer of uniform thickness, as represented in the Willett et al models. We demonstrate this model using time-lapse movies of a sand wedge above a mylar subducting plate. We use particle image velocimetry (PIV) to show the evolution of strain and structure within the overriding plate. Material accreted to the tapered end of the overriding plate drives deformation and causes

Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins

Directory of Open Access Journals (Sweden)

A. Voigt

2012-12-01

Full Text Available The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO₂ and a critical sea-ice cover (SI, both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO₂, SI^*, differs greatly among climate models. Here, we study the effect of bare sea-ice albedo, sea-ice dynamics and ocean heat transport on (CO₂, SI^* in the atmosphere–ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma continents and solar insolation (94% of modern. In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO₂, SI^* ≈ (500 ppm, 55%. Replacing the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO₂, SI^* ≈ (204 ppm, 70%. This is consistent with previous work and results from net evaporation and local melting near the sea-ice margin. When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO₂: (CO₂, SI^* ≈ (2 ppm, 85%. Therefore, the simulation of sea-ice dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO₂ for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-ice cover and only slightly decreases the critical CO₂. For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-ice cover therefore is a soft Snowball state rather than a true

Feynman variance for neutrons emitted from photo-fission initiated fission chains - a systematic simulation for selected speacal nuclear materials

Energy Technology Data Exchange (ETDEWEB)

Soltz, R. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Danagoulian, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sheets, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Korbly, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hartouni, E. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2013-05-22

Theoretical calculations indicate that the value of the Feynman variance, Y2F for the emitted distribution of neutrons from ssionable exhibits a strong monotonic de- pendence on a the multiplication, M, of a quantity of special nuclear material. In 2012 we performed a series of measurements at the Passport Inc. facility using a 9- MeV bremsstrahlung CW beam of photons incident on small quantities of uranium with liquid scintillator detectors. For the set of objects studies we observed deviations in the expected monotonic dependence, and these deviations were later con rmed by MCNP simulations. In this report, we modify the theory to account for the contri- bution from the initial photo- ssion and benchmark the new theory with a series of MCNP simulations on DU, LEU, and HEU objects spanning a wide range of masses and multiplication values.

Numerical simulation of laser shock in the presence of the initial state due to welding

International Nuclear Information System (INIS)

Julan, Emricka

2014-01-01

Surface treatments as laser shock peening offer the possibility to reduce tensile stresses or to generate compressive stresses in order to prevent crack initiation or reduce crack growth rate in particular in the areas where tension weld residual stresses are present. Laser shock peening may be applied on different metallic components to prevent stress corrosion cracking of Inconel 600 and high cycle thermal fatigue of austenitic stainless steels. The main aim of the PhD thesis is to develop the numerical simulation of laser peening. In the first section, axisymmetrical and 3D numerical models for one or several pulses have been developed in Code Aster and Europlexus softwares. These models were validated by experimental tests carried out in PIMM-ENSAM laboratory. Parameters identification of Johnson-Cook constitutive law was carried out for Inconel 600 at high strain rates. Moreover a new test was proposed which allowed proving the isotropic behavior of Inconel 600 at high strain rates. A modification of the Johnson-Cook constitutive law was also proposed, to take into account in a new way the sensitivity of the law to high strain rates. The second section of the thesis concerns a study on the effect of an initial state of welding on residual stresses after application of laser peening. We could conclude that this initial state has no strong influence on final residual stresses. Finally, a qualitative study on the effect of strain hardening induced by laser peening on fatigue life of stainless steels was undertaken, which shows the advantage of laser peening on shot peening due to smaller strain hardening created by laser peening. (author)

Plausibility of stromal initiation of epithelial cancers without a mutation in the epithelium: a computer simulation of morphostats

Directory of Open Access Journals (Sweden)

Cappuccio Antonio

2009-03-01

Full Text Available Abstract Background There is experimental evidence from animal models favoring the notion that the disruption of interactions between stroma and epithelium plays an important role in the initiation of carcinogenesis. These disrupted interactions are hypothesized to be mediated by molecules, termed morphostats, which diffuse through the tissue to determine cell phenotype and maintain tissue architecture. Methods We developed a computer simulation based on simple properties of cell renewal and morphostats. Results Under the computer simulation, the disruption of the morphostat gradient in the stroma generated epithelial precursors of cancer without any mutation in the epithelium. Conclusion The model is consistent with the possibility that the accumulation of genetic and epigenetic changes found in tumors could arise after the formation of a founder population of aberrant cells, defined as cells that are created by low or insufficient morphostat levels and that no longer respond to morphostat concentrations. Because the model is biologically plausible, we hope that these results will stimulate further experiments.

Using simulation to educate police about mental illness: A collaborative initiative

Directory of Open Access Journals (Sweden)

Wendy Stanyon

2014-06-01

Full Text Available Mental illness is a major public health concern in Canada and also globally. According to the World Health Organization, five of the top ten disabilities worldwide are mental health disorders. Within Canada, one in five individuals is living with mental illness each year. Currently, there are 6.7 million Canadians living with mental illness and over 1 million Canadian youth living with mental illness. Police are frequently the first responders to situations in the community involving people with mental illness, and police services are increasingly aware of the need to provide officers with additional training and strategies for effectively interacting with these citizens. This study examined the effectiveness of four online, interactive video-based simulations designed to educate police officers about mental illness and strategies for interacting with people with mental illness. The simulations were created through the efforts of a unique partnership involving a police service, a mental health facility and two postsecondary institutions. Frontline police officers from Ontario were divided into one of three groups (simulation, face to face, control. Using a pre- and post-test questionnaire, the groups were compared on their level of knowledge and understanding of mental illness. In addition, focus groups explored the impact of the simulations on officers’ level of confidence in engaging with individuals with mental illness and officers’ perceptions of the simulations’ ease of use and level of realism. The study’s findings determined that the simulations were just as effective as face-to-face learning, and the officers reported the simulations were easy to use and reflected real-life scenarios they had encountered on the job. As mental health continues to be a major public concern, not only in Canada but also globally, interactive simulations may provide an effective and affordable education resource not only for police officers but for

SIMULATION OF CARS ACCUMULATION PROCESSES FOR SOLVING TASKS OF OPERATIONAL PLANNING IN CONDITIONS OF INITIAL INFORMATION UNCERTAINTY

Directory of Open Access Journals (Sweden)

О. A. Tereshchenko

2017-06-01

Full Text Available Purpose. The article highlights development of the methodological basis for simulation the processes of cars accumulation in solving operational planning problems under conditions of initial information uncertainty for assessing the sustainability of the adopted planning scenario and calculating the associated technological risks. Methodology. The solution of the problem under investigation is based on the use of general scientific approaches, the apparatus of probability theory and the theory of fuzzy sets. To achieve this purpose, the factors influencing the entropy of operational plans are systematized. It is established that when planning the operational work of railway stations, sections and nodes, the most significant factors that cause uncertainty in the initial information are: a external conditions with respect to the railway ground in question, expressed by the uncertainty of the timing of cars arrivals; b external, hard-to-identify goals for the functioning of other participants in the logistics chain (primarily customers, expressed by the uncertainty of the completion time with the freight cars. These factors are suggested to be taken into account in automated planning through statistical analysis – the establishment and study of the remaining time (prediction errors. As a result, analytical dependencies are proposed for rational representation of the probability density functions of the time residual distribution in the form of point, piecewise-defined and continuous analytic models. The developed models of cars accumulation, the application of which depends on the identified states of the predicted incoming car flow to the accumulation system, are presented below. In addition, the last proposed model is a general case of models of accumulation processes with an arbitrary level of reliability of the initial information for any structure of the incoming flow of cars. In conclusion, a technique for estimating the results of

Steered molecular dynamics simulations of a type IV pilus probe initial stages of a force-induced conformational transition.

Directory of Open Access Journals (Sweden)

Joseph L Baker

2013-04-01

Full Text Available Type IV pili are long, protein filaments built from a repeating subunit that protrudes from the surface of a wide variety of infectious bacteria. They are implicated in a vast array of functions, ranging from bacterial motility to microcolony formation to infection. One of the most well-studied type IV filaments is the gonococcal type IV pilus (GC-T4P from Neisseria gonorrhoeae, the causative agent of gonorrhea. Cryo-electron microscopy has been used to construct a model of this filament, offering insights into the structure of type IV pili. In addition, experiments have demonstrated that GC-T4P can withstand very large tension forces, and transition to a force-induced conformation. However, the details of force-generation, and the atomic-level characteristics of the force-induced conformation, are unknown. Here, steered molecular dynamics (SMD simulation was used to exert a force in silico on an 18 subunit segment of GC-T4P to address questions regarding the nature of the interactions that lead to the extraordinary strength of bacterial pili. SMD simulations revealed that the buried pilin α1 domains maintain hydrophobic contacts with one another within the core of the filament, leading to GC-T4P's structural stability. At the filament surface, gaps between pilin globular head domains in both the native and pulled states provide water accessible routes between the external environment and the interior of the filament, allowing water to access the pilin α1 domains as reported for VC-T4P in deuterium exchange experiments. Results were also compared to the experimentally observed force-induced conformation. In particular, an exposed amino acid sequence in the experimentally stretched filament was also found to become exposed during the SMD simulations, suggesting that initial stages of the force induced transition are well captured. Furthermore, a second sequence was shown to be initially hidden in the native filament and became exposed upon

Steered molecular dynamics simulations of a type IV pilus probe initial stages of a force-induced conformational transition.

Science.gov (United States)

Baker, Joseph L; Biais, Nicolas; Tama, Florence

2013-04-01

Type IV pili are long, protein filaments built from a repeating subunit that protrudes from the surface of a wide variety of infectious bacteria. They are implicated in a vast array of functions, ranging from bacterial motility to microcolony formation to infection. One of the most well-studied type IV filaments is the gonococcal type IV pilus (GC-T4P) from Neisseria gonorrhoeae, the causative agent of gonorrhea. Cryo-electron microscopy has been used to construct a model of this filament, offering insights into the structure of type IV pili. In addition, experiments have demonstrated that GC-T4P can withstand very large tension forces, and transition to a force-induced conformation. However, the details of force-generation, and the atomic-level characteristics of the force-induced conformation, are unknown. Here, steered molecular dynamics (SMD) simulation was used to exert a force in silico on an 18 subunit segment of GC-T4P to address questions regarding the nature of the interactions that lead to the extraordinary strength of bacterial pili. SMD simulations revealed that the buried pilin α1 domains maintain hydrophobic contacts with one another within the core of the filament, leading to GC-T4P's structural stability. At the filament surface, gaps between pilin globular head domains in both the native and pulled states provide water accessible routes between the external environment and the interior of the filament, allowing water to access the pilin α1 domains as reported for VC-T4P in deuterium exchange experiments. Results were also compared to the experimentally observed force-induced conformation. In particular, an exposed amino acid sequence in the experimentally stretched filament was also found to become exposed during the SMD simulations, suggesting that initial stages of the force induced transition are well captured. Furthermore, a second sequence was shown to be initially hidden in the native filament and became exposed upon stretching.

Mathematical Constraints on the Use of Transmission Line Models for Simulating Initial Breakdown Pulses in Lightning Discharges

Science.gov (United States)

da Silva, C. L.; Merrill, R. A.; Pasko, V. P.

2015-12-01

A significant portion of the in-cloud lightning development is observed as a series of initial breakdown pulses (IBPs) that are characterized by an abrupt change in the electric field at a remote sensor. Recent experimental and theoretical studies have attributed this process to the stepwise elongation of an initial lightning leader inside the thunderstorm [da Silva and Pasko, JGR, 120, 4989-5009, 2015, and references therein]. Attempts to visually observe these events are hampered due to the fact that clouds are opaque to optical radiation. Due to this reason, throughout the last decade, a number of researchers have used the so-called transmission line models (also commonly referred to as engineering models), widely employed for return stroke simulations, to simulate the waveshapes of IBPs, and also of narrow bipolar events. The transmission line (TL) model approach is to prescribe the source current dynamics in a certain manner to match the measured E-field change waveform, with the purpose of retrieving key information about the source, such as its height, peak current, size, speed of charge motion, etc. Although the TL matching method is not necessarily physics-driven, the estimated source characteristics can give insights on the dominant length- and time-scales, as well as, on the energetics of the source. This contributes to better understanding of the environment where the onset and early stages of lightning development takes place.In the present work, we use numerical modeling to constrain the number of source parameters that can be confidently inferred from the observed far-field IBP waveforms. We compare different modified TL models (i.e., with different attenuation behaviors) to show that they tend to produce similar waveforms in conditions where the channel is short. We also demonstrate that it is impossible to simultaneously retrieve the speed of source current propagation and channel length from an observed IBP waveform, in contrast to what has been

Toward verifying fossil fuel CO2 emissions with the CMAQ model: motivation, model description and initial simulation.

Science.gov (United States)

Liu, Zhen; Bambha, Ray P; Pinto, Joseph P; Zeng, Tao; Boylan, Jim; Huang, Maoyi; Lei, Huimin; Zhao, Chun; Liu, Shishi; Mao, Jiafu; Schwalm, Christopher R; Shi, Xiaoying; Wei, Yaxing; Michelsen, Hope A

2014-04-01

Motivated by the question of whether and how a state-of-the-art regional chemical transport model (CTM) can facilitate characterization of CO2 spatiotemporal variability and verify CO2 fossil-fuel emissions, we for the first time applied the Community Multiscale Air Quality (CMAQ) model to simulate CO2. This paper presents methods, input data, and initial results for CO2 simulation using CMAQ over the contiguous United States in October 2007. Modeling experiments have been performed to understand the roles of fossil-fuel emissions, biosphere-atmosphere exchange, and meteorology in regulating the spatial distribution of CO2 near the surface over the contiguous United States. Three sets of net ecosystem exchange (NEE) fluxes were used as input to assess the impact of uncertainty of NEE on CO2 concentrations simulated by CMAQ. Observational data from six tall tower sites across the country were used to evaluate model performance. In particular, at the Boulder Atmospheric Observatory (BAO), a tall tower site that receives urban emissions from Denver CO, the CMAQ model using hourly varying, high-resolution CO2 fossil-fuel emissions from the Vulcan inventory and Carbon Tracker optimized NEE reproduced the observed diurnal profile of CO2 reasonably well but with a low bias in the early morning. The spatial distribution of CO2 was found to correlate with NO(x), SO2, and CO, because of their similar fossil-fuel emission sources and common transport processes. These initial results from CMAQ demonstrate the potential of using a regional CTM to help interpret CO2 observations and understand CO2 variability in space and time. The ability to simulate a full suite of air pollutants in CMAQ will also facilitate investigations of their use as tracers for CO2 source attribution. This work serves as a proof of concept and the foundation for more comprehensive examinations of CO2 spatiotemporal variability and various uncertainties in the future. Atmospheric CO2 has long been modeled

Precursor Evolution and Stress Corrosion Cracking Initiation of Cold-Worked Alloy 690 in Simulated Pressurized Water Reactor Primary Water

Energy Technology Data Exchange (ETDEWEB)

Zhai, Ziqing [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Toloczko, Mychailo [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Kruska, Karen [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Bruemmer, Stephen [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.

2017-05-22

Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 (UNS N06690) materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for either the 21% or 31%CW CLT specimens loaded at their yield stress after ~9,220 hours, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showed DCPD-indicated crack initiation after 10,400 hours of exposure at constant stress intensity, which was resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and discusses their effects on crack initiation in CW alloy 690.

OPM: The Open Porous Media Initiative

Science.gov (United States)

Flemisch, B.; Flornes, K. M.; Lie, K.; Rasmussen, A.

2011-12-01

The principal objective of the Open Porous Media (OPM) initiative is to develop a simulation suite that is capable of modeling industrially and scientifically relevant flow and transport processes in porous media and bridge the gap between the different application areas of porous media modeling, including reservoir mechanics, CO2 sequestration, biological systems, and product development of engineered media. The OPM initiative will provide a long-lasting, efficient, and well-maintained open-source software for flow and transport in porous media built on modern software principles. The suite is released under the GNU General Public License (GPL). Our motivation is to provide a means to unite industry and public research on simulation of flow and transport in porous media. For academic users, we seek to provide a software infrastructure that facilitates testing of new ideas on models with industry-standard complexity, while at the same time giving the researcher control over discretization and solvers. Similarly, we aim to accelerate the technology transfer from academic institutions to professional companies by making new research results available as free software of professional standard. The OPM initiative is currently supported by six research groups in Norway and Germany and funded by existing grants from public research agencies as well as from Statoil Petroleum and Total E&P Norge. However, a full-scale development of the OPM initiative requires substantially more funding and involvement of more research groups and potential end users. In this talk, we will provide an overview of the current activities in the OPM initiative. Special emphasis will be given to the demonstration of the synergies achieved by combining the strengths of individual open-source software components. In particular, a new fully implicit solver developed within the DUNE-based simulator DuMux could be enhanced by the ability to read industry-standard Eclipse input files and to run on

Model simulation studies to clarify the effect on saccadic eye movements of initial condition velocities set by the Vestibular Ocular Reflex (VOR)

Science.gov (United States)

Nam, M. H.; Winters, J. M.; Stark, L.

1981-01-01

Voluntary active head rotations produced vestibulo-ocular reflex eye movements (VOR) with the subject viewing a fixation target. When this target jumped, the size of the refixation saccades were a function of the ongoing initial velocity of the eye. Saccades made against the VOR were larger in magnitude. Simulation of a reciprocally innervated model eye movement provided results comparable to the experimental data. Most of the experimental effect appeared to be due to linear summation for saccades of 5 and 10 degree magnitude. For small saccades of 2.5 degrees, peripheral nonlinear interaction of state variables in the neuromuscular plant also played a role as proven by comparable behavior in the simulated model with known controller signals.

Calculation of free-energy differences from computer simulations of initial and final states

International Nuclear Information System (INIS)

Hummer, G.; Szabo, A.

1996-01-01

A class of simple expressions of increasing accuracy for the free-energy difference between two states is derived based on numerical thermodynamic integration. The implementation of these formulas requires simulations of the initial and final (and possibly a few intermediate) states. They involve higher free-energy derivatives at these states which are related to the moments of the probability distribution of the perturbation. Given a specified number of such derivatives, these integration formulas are optimal in the sense that they are exact to the highest possible order of free-energy perturbation theory. The utility of this approach is illustrated for the hydration free energy of water. This problem provides a quite stringent test because the free energy is a highly nonlinear function of the charge so that even fourth order perturbation theory gives a very poor estimate of the free-energy change. Our results should prove most useful for complex, computationally demanding problems where free-energy differences arise primarily from changes in the electrostatic interactions (e.g., electron transfer, charging of ions, protonation of amino acids in proteins). copyright 1996 American Institute of Physics

Dependence of hotspot initiation on void distribution in high explosive crystals simulated with molecular dynamics

Science.gov (United States)

Herring, Stuart Davis

Microscopic defects may dramatically affect the susceptibility of high explosives to shock initiation. Such defects redirect the shock's energy and become hotspots (concentrations of stress and heat) that can initiate chemical reactions. Sufficiently large or numerous defects may produce a self-sustaining deflagration or even detonation from a shock notably too weak to detonate defect-free samples. The effects of circular or spherical voids on the shock sensitivity of a model (two- or three-dimensional) high explosive crystal are considered. We simulate a piston impact using molecular dynamics with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. In both dimensionalities, the probability of initiating chemical reactions rises more suddenly with increasing piston velocity for larger voids that collapse more deterministically. A void of even 10 nm radius (˜39 interatomic spacings) reduces the minimum initiating velocity by a factor of 4 (8 in 3D). The transition at larger velocities to detonation is studied in micron-long samples with a single void (and its periodic images). Reactions during the shock traversal increase rapidly with velocity, then become a reliable detonation. In 2D, a void of radius 2.5 nm reduces the critical velocity by 10% from the perfect crystal; a Pop plot of the detonation delays at higher velocities shows a characteristic pressure dependence. 3D samples are more likely to react but less to detonate. In square lattices of voids, reducing the (common) void radius or increasing the porosity without changing the other parameter causes the hotspots to consume the material faster and detonation to occur sooner and at lower velocities. Early behavior is seen to follow a very simple ignition and growth model; the pressure exponents are more realistic than with single voids. The hotspots collectively develop a broad pressure wave (a sonic, diffuse deflagration front

GEAN T4 Simulations of Electromagnetic Showers Initiated by 30MeV y-Rays Entering the Atmosphere at Different Altitudes

International Nuclear Information System (INIS)

Akopov, N.; Grigoryan, A.; Karyan, G.

2017-01-01

The aim of this paper is to investigate the GEANT4 simulation for electromagnetic showers initiated by 30 MeV photons entering into the atmosphere at different altitudes (h). Charged and neutral components of the shower have been studied in various radial slices (R) with the detecting level corresponding to the altitude of Aragats mount, where the experimental setups of Cosmic Ray Division (CRD) of Yerevan Physics Institute (YerPhI) are operating. Qualitative observations of the energy spectra, as well as the tabulated parameters describing the fluxes at different values of h and R are used to make a comparison with those from the experimental data. The experimental data on particle fluxes are considered to be correlated with the atmospheric conditions such as pressure, temperature, presence of the charged clouds initiating the lightnings etc. (author)

Out-of pile mechanical test: simulating reactivity initiated accident (RIA) of zircaloy-4 cladding tube

Energy Technology Data Exchange (ETDEWEB)

Lee, Myung Ho; Kim, Jun Hwan; Choi, Byoung Kwon; Jeong, Young Hwan [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2004-07-01

The ejection or drop of a control rod in a reactivity initiated accident (RIA) causes a sudden increase in reactor power and in turn deposits a large amount of energy into the fuel. In a RIA, cladding tubes bear thermal expansion due to sudden reactivity and may fail from the resulting mechanical damage. Thus, RIA can be one of the safety margin reducers because the oxide on the tubes makes their thickness to support the load less as well as hydrides from the corrosion reduce the ductility of the tubes. In a RIA, the peak of reactor power from reactivity change is about 0.1m second and the temperature of the cladding tubes increases up to 1000 .deg. C in several seconds. Although it is hard to fully simulate the situation, several attempts to measure the change of mechanical properties under a RIA situation has done using a reduction coil, ring tension tests with high speed. This research was done to see the effect of oxide on the change of circumferential strength and ductility of Zircaloy-4 tubes in a RIA. The ring stretch tensile tests were performed with the strain rate of 1/sec and 0.01/s to simulate a transient of the cladding tube under a RIA. Since the test results of the ring tensile test are very sensitive to the lubricant, the tests were also carried out to select a suitable lubricant before the test of oxided specimens.

Spatial-temporal-covariance-based modeling, analysis, and simulation of aero-optics wavefront aberrations.

Science.gov (United States)

Vogel, Curtis R; Tyler, Glenn A; Wittich, Donald J

2014-07-01

We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrations that is based on spatial-temporal covariance matrices extracted from wavefront sensor measurements. Within this framework, we present a quasi-homogeneous structure function to analyze nonhomogeneous, mildly anisotropic spatial random processes, and we use this structure function to show that phase aberrations arising in aero-optics are, for an important range of operating parameters, locally Kolmogorov. This strongly suggests that the d5/3 power law for adaptive optics (AO) deformable mirror fitting error, where d denotes actuator separation, holds for certain important aero-optics scenarios. This framework also allows us to compute bounds on AO servo lag error and predictive control error. In addition, it provides us with the means to accurately simulate AO systems for the mitigation of aero-effects, and it may provide insight into underlying physical processes associated with turbulent flow. The techniques introduced here are demonstrated using data obtained from the Airborne Aero-Optics Laboratory.

A molecular fragment cheminformatics roadmap for mesoscopic simulation.

Science.gov (United States)

Truszkowski, Andreas; Daniel, Mirco; Kuhn, Hubert; Neumann, Stefan; Steinbeck, Christoph; Zielesny, Achim; Epple, Matthias

2014-12-01

Mesoscopic simulation studies the structure, dynamics and properties of large molecular ensembles with millions of atoms: Its basic interacting units (beads) are no longer the nuclei and electrons of quantum chemical ab-initio calculations or the atom types of molecular mechanics but molecular fragments, molecules or even larger molecular entities. For its simulation setup and output a mesoscopic simulation kernel software uses abstract matrix (array) representations for bead topology and connectivity. Therefore a pure kernel-based mesoscopic simulation task is a tedious, time-consuming and error-prone venture that limits its practical use and application. A consequent cheminformatics approach tackles these problems and provides solutions for a considerably enhanced accessibility. This study aims at outlining a complete cheminformatics roadmap that frames a mesoscopic Molecular Fragment Dynamics (MFD) simulation kernel to allow its efficient use and practical application. The molecular fragment cheminformatics roadmap consists of four consecutive building blocks: An adequate fragment structure representation (1), defined operations on these fragment structures (2), the description of compartments with defined compositions and structural alignments (3), and the graphical setup and analysis of a whole simulation box (4). The basis of the cheminformatics approach (i.e. building block 1) is a SMILES-like line notation (denoted f SMILES) with connected molecular fragments to represent a molecular structure. The f SMILES notation and the following concepts and methods for building blocks 2-4 are outlined with examples and practical usage scenarios. It is shown that the requirements of the roadmap may be partly covered by already existing open-source cheminformatics software. Mesoscopic simulation techniques like MFD may be considerably alleviated and broadened for practical use with a consequent cheminformatics layer that successfully tackles its setup subtleties and

Evaluation of the effect of initial texture on the development of deformation texture

DEFF Research Database (Denmark)

Leffers, Torben; Juul Jensen, Dorte

1986-01-01

The authors describe a computer procedure which allows them to introduce experimental initial textures as starting conditions for texture simulation (instead of a theoretical random texture). They apply the procedure on two batches of copper with weak initial textures and on fine-grained and coarse......-grained aluminium with moderately strong initial textures. In copper the initial texture turns out to be too weak to have any significant effect. In aluminium the initial texture has a very significant effect on the simulated textures-similar to the effect it has on the experimental textures. However......, there are differences between the simulated and the experimental aluminium textures that can only be explained as a grain-size effect. Possible future applications of the procedure are discussed...

Systemic characterization and evaluation of particle packings as initial sets for discrete element simulations

Science.gov (United States)

Morfa, Carlos Recarey; Cortés, Lucía Argüelles; Farias, Márcio Muniz de; Morales, Irvin Pablo Pérez; Valera, Roberto Roselló; Oñate, Eugenio

2018-07-01

A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension and shape of particles, space occupation, homogeneity, connectivity and isotropy, among others. This classification and integration of several properties allows to carry out a characterization process to systemically evaluate the particle packings in order to guarantee the quality of the initial meshes in discrete element simulations, in both the micro- and the macroscales. Several new properties were created, and improvements in existing ones are presented. Properties from other disciplines were adapted to be used in the evaluation of particle systems. The methodology allows to easily characterize media at the level of the microscale (continuous geometries—steels, rocks microstructures, etc., and discrete geometries) and the macroscale. A global, systemic and integral system for characterizing and evaluating particle sets, based on fuzzy logic, is presented. Such system allows researchers to have a unique evaluation criterion based on the aim of their research. Examples of applications are shown.

Systemic characterization and evaluation of particle packings as initial sets for discrete element simulations

Science.gov (United States)

Morfa, Carlos Recarey; Cortés, Lucía Argüelles; Farias, Márcio Muniz de; Morales, Irvin Pablo Pérez; Valera, Roberto Roselló; Oñate, Eugenio

2017-10-01

A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension and shape of particles, space occupation, homogeneity, connectivity and isotropy, among others. This classification and integration of several properties allows to carry out a characterization process to systemically evaluate the particle packings in order to guarantee the quality of the initial meshes in discrete element simulations, in both the micro- and the macroscales. Several new properties were created, and improvements in existing ones are presented. Properties from other disciplines were adapted to be used in the evaluation of particle systems. The methodology allows to easily characterize media at the level of the microscale (continuous geometries—steels, rocks microstructures, etc., and discrete geometries) and the macroscale. A global, systemic and integral system for characterizing and evaluating particle sets, based on fuzzy logic, is presented. Such system allows researchers to have a unique evaluation criterion based on the aim of their research. Examples of applications are shown.

Tree Simulation Techniques for Integrated Safety Assessment

International Nuclear Information System (INIS)

Melendez Asensio, E.; Izquierdo Rocha, J.M.; Sanchez Perez, M.; Hortal Reymundo, J.; Perez Mulas, A.

1999-01-01

In the development of a PSA a central role is played by the construction of the event trees that, stemming from each initiating event considered, will finally lead to the calculation of the core damage frequency (CDF). This construction is extensively done by means of expert judgement, performing simulation of the sequences only when some doubt arises (typically for small break LOCAs) using integrated codes. Transient analysis done within the framework of the PSA has important simplifications that affect the transient simulation, specially in relation with the control and protection systems, and may not identify complicated sequences. Specialised simulation tools such as RELAP5 have been used only at very specific points of the PSAs due to time and model complexity constraints. On the other hand, a large amount of work and expertise has been laid in the development of simulation tools, independently of the PSA effort. Tools simplified in the phenomena they consider, but complete in the treatment of automatic and manual control and protection systems are now available for automatic generation and testing of the sequences appearing in the Event Trees. Additionally, an increasing effort and interest has been spent in the development of efficient means for the representation of the Emergency Operating Procedures, which, incorporated into the simulating tool would make a more realistic picture of the real plant performance. At present; both types of analyses - transient and probabilistic - can converge to be able to dynamically generate an Event Tree while taking into account the actual performance of the control and protection systems of the plant and the operator actions. Such a tool would allow for an assessment of the Event Trees, and, if fed with probabilistic data, can provide results of the same nature. Key aspects of this approach that imply new theoretical as well as practical developments in addition to those traditionally covered by classical simulation

CAISSON: Interconnect Network Simulator

Science.gov (United States)

Springer, Paul L.

2006-01-01

Cray response to HPCS initiative. Model future petaflop computer interconnect. Parallel discrete event simulation techniques for large scale network simulation. Built on WarpIV engine. Run on laptop and Altix 3000. Can be sized up to 1000 simulated nodes per host node. Good parallel scaling characteristics. Flexible: multiple injectors, arbitration strategies, queue iterators, network topologies.

Validity of spherical approximations of initial charge cloud shape in silicon detectors

International Nuclear Information System (INIS)

Xu Cheng; Danielsson, Mats; Bornefalk, Hans

2011-01-01

Spherical approximation has been used extensively in low-energy X-ray imaging to represent the initial charge cloud produced by photon interactions in silicon detectors, mainly because of its simplicity. However, for high-energy X-rays, where the initial charge distribution is as important as the diffusion process, the spherical approximation will not result in a realistic detector response. In this paper, we present a bubble-line model that simulates the initial charge cloud in silicon detectors for photons in the energy range of medical imaging. An initial charge cloud can be generated by sampling the center of gravity and the track size from statistical distributions derived from Monte Carlo generated tracks and by distributing a certain proportion of photon energy into a bubble (68%) and a line portion uniformly. The simulations of detector response demonstrate that the new model simulates the detector response accurately and corresponds well to Monte Carlo simulation.

Ozone-Initiated Chemistry in an Occupied Simulated Aircraft Cabin

DEFF Research Database (Denmark)

Weschler, Charles J.; Wisthaler, Armin; Cowlin, Shannon

2007-01-01

We have used multiple analytical methods to characterize the gas-phase products formed when ozone was added to cabin air during simulated 4-hour flights that were conducted in a reconstructed section of a B-767 aircraft containing human occupants. Two separate groups of 16 females were each expos...

Optimal timing of viral load monitoring during pregnancy to predict viraemia at delivery in HIV-infected women initiating ART in South Africa: a simulation study.

Science.gov (United States)

Lesosky, Maia; Glass, Tracy; Mukonda, Elton; Hsiao, Nei-Yuan; Abrams, Elaine J; Myer, Landon

2017-11-01

HIV viral load (VL) monitoring is a central tool to evaluate ART effectiveness and transmission risk. There is a global movement to expand VL monitoring following recent recommendations from the World Health Organization (WHO), but there has been little research into VL monitoring in pregnant women. We investigated one important question in this area: when and how frequently VL should be monitored in women initiating ART during pregnancy to predict VL at the time of delivery in a simulated South African population. We developed a mathematical model simulating VL from conception through delivery using VL data from the Maternal and Child Health - Antiretroviral Therapy (MCH-ART) cohort. VL was modelled based on three major compartments: pre-ART VL, viral decay immediately after ART initiation and viral maintenance (including viral suppression and viraemic episodes). Using this simulation, we examined the performance of various VL monitoring schema in predicting elevated VL at delivery. If WHO guidelines for non-pregnant adults were used, the majority of HIV-infected pregnant women (69%) would not receive a VL test during pregnancy. Most models that based VL monitoring in pregnancy on the time elapsed since ART initiation (regardless of gestation) performed poorly (sensitivity pregnancy on the woman's gestation (regardless of time on ART) appeared to perform better overall (sensitivity >60%). Across all permutations, inclusion of pre-ART VL values had a negligible impact on predictive performance (improving test sensitivity and specificity pregnancy, supporting better integration of maternal and HIV health services. Testing turnaround times require careful consideration, and point-of-care VL testing may be the best approach for measuring VL at delivery. Broadening the scope of this simulation model in the light of current scale up of VL monitoring in high burden countries is important. © 2017 The Authors. Journal of the International AIDS Society published by John

Simulation of Fatigue Crack Initiation at Corrosion Pits With EDM Notches

Science.gov (United States)

Smith, Stephen W.; Newman, John A.; Piascik, Robert S.

2003-01-01

Uniaxial fatigue tests were conducted to compare the fatigue life of laboratory produced corrosion pits, similar to those observed in the shuttle main landing gear wheel bolt-hole, and an electro-discharged-machined (EDM) flaw. EDM Jaws are used to simulate corrosion pits during shuttle wheel (dynamometer) testing. The aluminum alloy, (AA 7050) laboratory fatigue tests were conducted to simulate the local stress level contained in the wheel bolt-hole. Under this high local stress condition, the EDM notch produced a fatigue life similar to test specimens containing corrosion pits of similar size. Based on the laboratory fatigue test results, the EDM Jaw (semi-circular disc shaped) produces a local stress state similar to corrosion pits and can be used to simulate a corrosion pit during the shuttle wheel dynamometer tests.

1D numerical simulation of charge trapping in an insulator submitted to an electron beam irradiation. Part I: Computation of the initial secondary electron emission yield

International Nuclear Information System (INIS)

Aoufi, A.; Damamme, G.

2011-01-01

The aim of this work is to study by numerical simulation a mathematical modelling technique describing charge trapping during initial charge injection in an insulator submitted to electron beam irradiation. A two-fluxes method described by a set of two stationary transport equations is used to split the electron current j e (z) into coupled forward j e+ (z) and backward j e (z) currents and such that j e (z) = j e+ (z) - j e- (z). The sparse algebraic linear system, resulting from the vertex-centered finite-volume discretization scheme is solved by an iterative decoupled fixed point method which involves the direct inversion of a bi-diagonal matrix. The sensitivity of the initial secondary electron emission yield with respect to the energy of incident primary electrons beam, that is penetration depth of the incident beam, or electron cross sections (absorption and diffusion) is investigated by numerical simulations. (authors)

Development of simulators for SMRs

International Nuclear Information System (INIS)

Jafri, M.N.; Butt, P.

1998-01-01

The first step towards the introduction of simulator culture in Pakistan Atomic Energy Commission (PAEC) was taken in 1976 when the work on the development of analog computer based Basic Principles Simulator of KANUPP was initiated to test the Modified Real Time Control software. The project was revitalized in 1988 to develop a digital computer model of major KANUPP systems along with real-time simulation executive software and man-machine interface software in FORTRAN-77 on VAX-11/780. This simulator was later ported on microcomputers using C-language with four display units, entitled as KANUPP Test Simulator (KTS), and is presently being employed for training and teaching at KANUPP Inplant Plant Training Center(INPTC) and Institute of Nuclear Power Engineering (KINPOE) respectively. The acquisition of Advanced Process Simulator Software (APROS) in 1991 laid the foundation for establishing an enhanced simulator environment to meet the present day requirements and scope of simulators. The development of APROS based Engineering Analyzer for KANUPP was initiated in 1992. With the contract for 300 MWe two loop PWR nuclear power plant from China the development of Full Scope Training Simulator for CHASNUPP-1 was initiated in 1993, which is scheduled to be completed in end 1997. The process of development of simulators for SMRs provided the opportunities to achieve indigenous capabilities for the design and development of control room with real time I/O interface, real time data communication using RTPs and a general purpose security guarded real-time graphics display system, as well as considerable experience on the design and development of SMRs simulators. This paper presents information on the present state of SMRs simulator development and the achievements made in PAEC. (author)

Primary Connections: Simulating the Classroom in Initial Teacher Education

Science.gov (United States)

Hume, Anne Christine

2012-01-01

The challenge of preparing novice primary teachers for teaching in an educational environment, where science education has low status and many teachers have limited science content knowledge and lack the confidence to teach science, is great. This paper reports on an innovation involving a sustained simulation in an undergraduate science education…

A New Heuristic Providing an Effective Initial Solution for a Simulated Annealing approach to Energy Resource Scheduling in Smart Grids

DEFF Research Database (Denmark)

Sousa, Tiago M; Morais, Hugo; Castro, R.

2014-01-01

scheduling problem. Therefore, the use of metaheuristics is required to obtain good solutions in a reasonable amount of time. This paper proposes two new heuristics, called naive electric vehicles charge and discharge allocation and generation tournament based on cost, developed to obtain an initial solution...... to be used in the energy resource scheduling methodology based on simulated annealing previously developed by the authors. The case study considers two scenarios with 1000 and 2000 electric vehicles connected in a distribution network. The proposed heuristics are compared with a deterministic approach...

Analysis of the Steam Generator Tubes Rupture Initiating Event

International Nuclear Information System (INIS)

Trillo, A.; Minguez, E.; Munoz, R.; Melendez, E.; Sanchez-Perea, M.; Izquierd, J.M.

1998-01-01

In PSA studies, Event Tree-Fault Tree techniques are used to analyse to consequences associated with the evolution of an initiating event. The Event Tree is built in the sequence identification stage, following the expected behaviour of the plant in a qualitative way. Computer simulation of the sequences is performed mainly to determine the allowed time for operator actions, and do not play a central role in ET validation. The simulation of the sequence evolution can instead be performed by using standard tools, helping the analyst obtain a more realistic ET. Long existing methods and tools can be used to automatism the construction of the event tree associated to a given initiator. These methods automatically construct the ET by simulating the plant behaviour following the initiator, allowing some of the systems to fail during the sequence evolution. Then, the sequences with and without the failure are followed. The outcome of all this is a Dynamic Event Tree. The work described here is the application of one such method to the particular case of the SGTR initiating event. The DYLAM scheduler, designed at the Ispra (Italy) JRC of the European Communities, is used to automatically drive the simulation of all the sequences constituting the Event Tree. Similarly to the static Event Tree, each time a system is demanded, two branches are open: one corresponding to the success and the other to the failure of the system. Both branches are followed by the plant simulator until a new system is demanded, and the process repeats. The plant simulation modelling allows the treatment of degraded sequences that enter into the severe accident domain as well as of success sequences in which long-term cooling is started. (Author)

Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: Model development and initial evaluation

International Nuclear Information System (INIS)

Zhang, Xuesong; Izaurralde, R. César; Arnold, Jeffrey G.; Williams, Jimmy R.; Srinivasan, Raghavan

2013-01-01

Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO 2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land–atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land–atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes. - Highlights: • Expanding the SWAT

Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: Model development and initial evaluation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xuesong; Izaurralde, R. César [Joint Global Change Research Institute, Pacific Northwest National Laboratory and University of Maryland, College Park, MD 20740 (United States); Arnold, Jeffrey G. [Grassland, Soil and Water Research Laboratory USDA-ARS, Temple, TX 76502 (United States); Williams, Jimmy R. [Blackland Research and Extension Center, AgriLIFE Research, 720 E. Blackland Road, Temple, TX 76502 (United States); Srinivasan, Raghavan [Spatial Sciences Laboratory in the Department of Ecosystem Science and Management, Texas A and M University, College Stations, TX 77845 (United States)

2013-10-01

Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO{sub 2} emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land–atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land–atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes. - Highlights: • Expanding the

Initial reconstruction results from a simulated adaptive small animal C shaped PET/MR insert

Energy Technology Data Exchange (ETDEWEB)

Efthimiou, Nikos [Technological Educational Institute of Athens (Greece); Kostou, Theodora; Papadimitroulas, Panagiotis [Technological Educational Institute of Athens (Greece); Department of Medical Physics, School of Medicine, University of Patras (Greece); Charalampos, Tsoumpas [Division of Biomedical Imaging, University of Leeds, Leeds (United Kingdom); Loudos, George [Technological Educational Institute of Athens (Greece)

2015-05-18

Traditionally, most clinical and preclinical PET scanners, rely on full cylindrical geometry for whole body as well as dedicated organ scans, which is not optimized with regards to sensitivity and resolution. Several groups proposed the construction of dedicated PET inserts for MR scanners, rather than the construction of new integrated PET/MR scanners. The space inside an MR scanner is a limiting factor which can be reduced further with the use of extra coils, and render the use of non-flexible cylindrical PET scanners difficult if not impossible. The incorporation of small SiPM arrays, can provide the means to design adaptive PET scanners to fit in tight locations, which, makes imaging possible and improve the sensitivity, due to the closer approximation to the organ of interest. In order to assess the performance of such a device we simulated the geometry of a C shaped PET, using GATE. The design of the C-PET was based on a realistic SiPM-BGO scenario. In order reconstruct the simulated data, with STIR, we had to calculate system probability matrix which corresponds to this non standard geometry. For this purpose we developed an efficient multi threaded ray tracing technique to calculate the line integral paths in voxel arrays. One of the major features is the ability to automatically adjust the size of FOV according to the geometry of the detectors. The initial results showed that the sensitivity improved as the angle between the detector arrays increases, thus better angular sampling the scanner's field of view (FOV). The more complete angular coverage helped in improving the shape of the source in the reconstructed images, as well. Furthermore, by adapting the FOV to the closer to the size of the source, the sensitivity per voxel is improved.

Initial reconstruction results from a simulated adaptive small animal C shaped PET/MR insert

International Nuclear Information System (INIS)

Efthimiou, Nikos; Kostou, Theodora; Papadimitroulas, Panagiotis; Charalampos, Tsoumpas; Loudos, George

2015-01-01

Traditionally, most clinical and preclinical PET scanners, rely on full cylindrical geometry for whole body as well as dedicated organ scans, which is not optimized with regards to sensitivity and resolution. Several groups proposed the construction of dedicated PET inserts for MR scanners, rather than the construction of new integrated PET/MR scanners. The space inside an MR scanner is a limiting factor which can be reduced further with the use of extra coils, and render the use of non-flexible cylindrical PET scanners difficult if not impossible. The incorporation of small SiPM arrays, can provide the means to design adaptive PET scanners to fit in tight locations, which, makes imaging possible and improve the sensitivity, due to the closer approximation to the organ of interest. In order to assess the performance of such a device we simulated the geometry of a C shaped PET, using GATE. The design of the C-PET was based on a realistic SiPM-BGO scenario. In order reconstruct the simulated data, with STIR, we had to calculate system probability matrix which corresponds to this non standard geometry. For this purpose we developed an efficient multi threaded ray tracing technique to calculate the line integral paths in voxel arrays. One of the major features is the ability to automatically adjust the size of FOV according to the geometry of the detectors. The initial results showed that the sensitivity improved as the angle between the detector arrays increases, thus better angular sampling the scanner's field of view (FOV). The more complete angular coverage helped in improving the shape of the source in the reconstructed images, as well. Furthermore, by adapting the FOV to the closer to the size of the source, the sensitivity per voxel is improved.

Simulating large-scale spiking neuronal networks with NEST

OpenAIRE

Schücker, Jannis; Eppler, Jochen Martin

2014-01-01

The Neural Simulation Tool NEST [1, www.nest-simulator.org] is the simulator for spiking neural networkmodels of the HBP that focuses on the dynamics, size and structure of neural systems rather than on theexact morphology of individual neurons. Its simulation kernel is written in C++ and it runs on computinghardware ranging from simple laptops to clusters and supercomputers with thousands of processor cores.The development of NEST is coordinated by the NEST Initiative [www.nest-initiative.or...

Simulating Shopper Behavior using Fuzzy Logic in Shopping Center Simulation

Directory of Open Access Journals (Sweden)

Jason Christian

2016-12-01

Full Text Available To simulate real-world phenomena, a computer tool can be used to run a simulation and provide a detailed report. By using a computer-aided simulation tool, we can retrieve information relevant to the simulated subject in a relatively short time. This study is an extended and complete version of an initial research done by Christian and Hansun and presents a prototype of a multi-agent shopping center simulation tool along with a fuzzy logic algorithm implemented in the system. Shopping centers and all their components are represented in a simulated 3D environment. The simulation tool was created using the Unity3D engine to build the 3D environment and to run the simulation. To model and simulate the behavior of agents inside the simulation, a fuzzy logic algorithm that uses the agents’ basic knowledge as input was built to determine the agents’ behavior inside the system and to simulate human behaviors as realistically as possible.

Neutronics and thermal-hydraulics coupling: some contributions toward an improved methodology to simulate the initiating phase of a severe accident in a sodium fast reactor

International Nuclear Information System (INIS)

Guyot, Maxime

2014-01-01

This project is dedicated to the analysis and the quantification of bias corresponding to the computational methodology for simulating the initiating phase of severe accidents on Sodium Fast Reactors. A deterministic approach is carried out to assess the consequences of a severe accident by adopting best estimate design evaluations. An objective of this deterministic approach is to provide guidance to mitigate severe accident developments and re-criticalities through the implementation of adequate design measures. These studies are generally based on modern simulation techniques to test and verify a given design. The new approach developed in this project aims to improve the safety assessment of Sodium Fast Reactors by decreasing the bias related to the deterministic analysis of severe accident scenarios. During the initiating phase, the subassembly wrapper tubes keep their mechanical integrity. Material disruption and dispersal is primarily one-dimensional. For this reason, evaluation methodology for the initiating phase relies on a multiple-channel approach. Typically a channel represents an average pin in a subassembly or a group of similar subassemblies. In the multiple-channel approach, the core thermal-hydraulics model is composed of 1 or 2 D channels. The thermal-hydraulics model is coupled to a neutronics module to provide an estimate of the reactor power level. In this project, a new computational model has been developed to extend the initiating phase modeling. This new model is based on a multi-physics coupling. This model has been applied to obtain information unavailable up to now in regards to neutronics and thermal-hydraulics models and their coupling. (author) [fr

Development of a MELCOR self-initialization algorithm for boiling water reactors

International Nuclear Information System (INIS)

Chien, C.S.; Wang, S.J.; Cheng, S.K.

1996-01-01

The MELCOR code, developed by Sandia National Laboratories, is suitable for calculating source terms and simulating severe accident phenomena of nuclear power plants. Prior to simulating a severe accident transient with MELCOR, the initial steady-state conditions must be generated in advance. The current MELCOR users' manuals do not provide a self-initialization procedure; this is the reason users have to adjust the initial conditions by themselves through a trial-and-error approach. A MELCOR self-initialization algorithm for boiling water reactor plants has been developed, which eliminates the tedious trial-and-error procedures and improves the simulation accuracy. This algorithm adjusts the important plant variable such as the dome pressure, downcomer level, and core flow rate to the desired conditions automatically. It is implemented through input with control functions provided in MELCOR. The reactor power and feedwater temperature are fed as input data. The initialization work of full-power conditions of the Kuosheng nuclear power station is cited as an example. These initial conditions are generated successfully with the developed algorithm. The generated initial conditions can be stored in a restart file and used for transient analysis. The methodology in this study improves the accuracy and consistency of transient calculations. Meanwhile, the algorithm provides all MELCOR users an easy and correct method for establishing the initial conditions

Numerical simulation of a possible counterexample to cosmic censorship

International Nuclear Information System (INIS)

Garfinkle, David

2004-01-01

A numerical simulation is presented here of the evolution of initial data of the kind that was conjectured by Hertog, Horowitz, and Maeda to be a violation of cosmic censorship. Those initial data are essentially a thick domain wall connecting two regions of anti-de Sitter space. The initial data have a free parameter that is the initial size of the wall. The simulation shows no violation of cosmic censorship, but rather the formation of a small black hole. The simulation described here is for a moderate wall size and leaves open the possibility that cosmic censorship might be violated for larger walls

On the System of Person-Denoting Signs in Estonian Sign Language: Estonian Name Signs

Science.gov (United States)

Paales, Liina

2010-01-01

This article discusses Estonian personal name signs. According to study there are four personal name sign categories in Estonian Sign Language: (1) arbitrary name signs; (2) descriptive name signs; (3) initialized-descriptive name signs; (4) loan/borrowed name signs. Mostly there are represented descriptive and borrowed personal name signs among…

Impact of Soil Moisture Initialization on Seasonal Weather Prediction

Science.gov (United States)

Koster, Randal D.; Suarez, Max J.; Houser, Paul (Technical Monitor)

2002-01-01

The potential role of soil moisture initialization in seasonal forecasting is illustrated through ensembles of simulations with the NASA Seasonal-to-Interannual Prediction Project (NSIPP) model. For each boreal summer during 1997-2001, we generated two 16-member ensembles of 3-month simulations. The first, "AMIP-style" ensemble establishes the degree to which a perfect prediction of SSTs would contribute to the seasonal prediction of precipitation and temperature over continents. The second ensemble is identical to the first, except that the land surface is also initialized with "realistic" soil moisture contents through the continuous prior application (within GCM simulations leading up to the start of the forecast period) of a daily observational precipitation data set and the associated avoidance of model drift through the scaling of all surface prognostic variables. A comparison of the two ensembles shows that soil moisture initialization has a statistically significant impact on summertime precipitation and temperature over only a handful of continental regions. These regions agree, to first order, with regions that satisfy three conditions: (1) a tendency toward large initial soil moisture anomalies, (2) a strong sensitivity of evaporation to soil moisture, and (3) a strong sensitivity of precipitation to evaporation. The degree to which the initialization improves forecasts relative to observations is mixed, reflecting a critical need for the continued development of model parameterizations and data analysis strategies.

Simulation-Based Training for Thoracoscopy

DEFF Research Database (Denmark)

Bjurström, Johanna Margareta; Konge, Lars; Lehnert, Per

2013-01-01

An increasing proportion of thoracic procedures are performed using video-assisted thoracic surgery. This minimally invasive technique places special demands on the surgeons. Using simulation-based training on artificial models or animals has been proposed to overcome the initial part of the lear......An increasing proportion of thoracic procedures are performed using video-assisted thoracic surgery. This minimally invasive technique places special demands on the surgeons. Using simulation-based training on artificial models or animals has been proposed to overcome the initial part...... of the learning curve. This study aimed to investigate the effect of simulation-based training and to compare self-guided and educator-guided training....

Multi-scale modelling of fatigue microcrack initiation

International Nuclear Information System (INIS)

Liu, Jia

2013-01-01

The thesis aims to improve the understanding and simulation of microcrack initiation induced by thermal fatigue and the induced crack network formation. The polycrystalline simulations allow the prediction of both macroscopic cyclic behavior and mean grain distributions of stress, plastic strain and number of cycles to microcrack initiation. Various aggregate meshes have been used, from the simplest ones using cubic grains up to a real 3D aggregate built thanks to many re-polishing and EBSD measurement sequences (Institut P', Poitiers). Tension-compression, cyclic shear and equi-biaxial loadings, with and without mean strain, have been considered. All the predictions are in qualitative agreement with many experimental observations obtained at various scales. The single crystal simulations allow us to predict the effect of slip localization in thin persistent slip bands (PSBs). Inside PSBs, vacancies are produced and annihilated because of cyclic dislocation interactions and may diffuse towards the surrounding matrix. This induces extrusion growth at the free surface of PSBs. Microcracking is modelled by cohesive zones located along the PSB - matrix interfaces. The predicted extrusion rates and numbers of cycles to microcrack initiation are in fair agreement with numerous experimental data concerning single and polycrystals, copper and 316L(N), under either air or inert environment. (author) [fr

Star formation in mergers with comologically motivated initial conditions

NARCIS (Netherlands)

Karman, Wouter; Macciò, Andrea V.; Kannan, Rahul; Moster, Benjamin P.; Somerville, Rachel S.

2015-01-01

We use semi-analytic models and cosmological merger trees to provide the initial conditions for multimerger numerical hydrodynamic simulations, and exploit these simulations to explore the effect of galaxy interaction and merging on star formation (SF). We compute numerical realizations of 12 merger

Initial state with shear in peripheral heavy ion collisions

Science.gov (United States)

Magas, V. K.; Gordillo, J.; Strottman, D.; Xie, Y. L.; Csernai, L. P.

2018-06-01

In the present work we propose a new way of constructing the initial state for further hydrodynamic simulation of relativistic heavy ion collisions based on Bjorken-like solution applied streak by streak in the transverse plane. Previous fluid dynamical calculations in Cartesian coordinates with an initial state based on a streak by streak Yang-Mills field led for peripheral higher energy collisions to large angular momentum, initial shear flow and significant local vorticity. Recent experiments verified the existence of this vorticity via the resulting polarization of emitted Λ and Λ ¯ particles. At the same time parton cascade models indicated the existence of more compact initial state configurations, which we are going to simulate in our approach. The proposed model satisfies all the conservation laws, including conservation of a strong initial angular momentum, which is present in noncentral collisions. As a consequence of this large initial angular momentum we observe the rotation of the whole system as well as the fluid shear in the initial state, which leads to large flow vorticity. Another advantage of the proposed model is that the initial state can be given in both [t,x,y,z] and [τ ,x ,y ,η ] coordinates and thus can be tested by all 3+1D hydrodynamical codes which exist in the field.

An introduction to LIME 1.0 and its use in coupling codes for multiphysics simulations.

Energy Technology Data Exchange (ETDEWEB)

Belcourt, Noel; Pawlowski, Roger Patrick; Schmidt, Rodney Cannon; Hooper, Russell Warren

2011-11-01

LIME is a small software package for creating multiphysics simulation codes. The name was formed as an acronym denoting 'Lightweight Integrating Multiphysics Environment for coupling codes.' LIME is intended to be especially useful when separate computer codes (which may be written in any standard computer language) already exist to solve different parts of a multiphysics problem. LIME provides the key high-level software (written in C++), a well defined approach (with example templates), and interface requirements to enable the assembly of multiple physics codes into a single coupled-multiphysics simulation code. In this report we introduce important software design characteristics of LIME, describe key components of a typical multiphysics application that might be created using LIME, and provide basic examples of its use - including the customized software that must be written by a user. We also describe the types of modifications that may be needed to individual physics codes in order for them to be incorporated into a LIME-based multiphysics application.

Reactor Subsystem Simulation for Nuclear Hybrid Energy Systems

Energy Technology Data Exchange (ETDEWEB)

Shannon Bragg-Sitton; J. Michael Doster; Alan Rominger

2012-09-01

Preliminary system models have been developed by Idaho National Laboratory researchers and are currently being enhanced to assess integrated system performance given multiple sources (e.g., nuclear + wind) and multiple applications (i.e., electricity + process heat). Initial efforts to integrate a Fortran-based simulation of a small modular reactor (SMR) with the balance of plant model have been completed in FY12. This initial effort takes advantage of an existing SMR model developed at North Carolina State University to provide initial integrated system simulation for a relatively low cost. The SMR subsystem simulation details are discussed in this report.

Superlubricity mechanism of diamond-like carbon with glycerol. Coupling of experimental and simulation studies

International Nuclear Information System (INIS)

Bouchet, M I De Barros; Matta, C; Le-Mogne, Th; Martin, J Michel; Zhang, Q; III, W Goddard; Kano, M; Mabuchi, Y; Ye, J

2007-01-01

We report a unique tribological system that produces superlubricity under boundary lubrication conditions with extremely little wear. This system is a thin coating of hydrogen-free amorphous Diamond-Like-Carbon (denoted as ta-C) at 353 K in a ta-C/ta-C friction pair lubricated with pure glycerol. To understand the mechanism of friction vanishing we performed ToF-SIMS experiments using deuterated glycerol and 13 C glycerol. This was complemented by first-principles-based computer simulations using the ReaxFF reactive force field to create an atomistic model of ta-C. These simulations show that DLC with the experimental density of 3.24 g/cc leads to an atomistic structure consisting of a 3D percolating network of tetrahedral (sp 3 ) carbons accounting for 71.5% of the total, in excellent agreement with the 70% deduced from our Auger spectroscopy and XANES experiments. The simulations show that the remaining carbons (with sp 2 and sp 1 character) attach in short chains of length 1 to 7. In sliding simulations including glycerol molecules, the surface atoms react readily to form a very smooth carbon surface containing OH-terminated groups. This agrees with our SIMS experiments. The simulations find that the OH atoms are mostly bound to surface sp 1 atoms leading to very flexible elastic response to sliding. Both simulations and experiments suggest that the origin of the superlubricity arises from the formation of this OH-terminated surface

Simulation Activity in Otolaryngology Residencies.

Science.gov (United States)

Deutsch, Ellen S; Wiet, Gregory J; Seidman, Michael; Hussey, Heather M; Malekzadeh, Sonya; Fried, Marvin P

2015-08-01

Simulation has become a valuable tool in medical education, and several specialties accept or require simulation as a resource for resident training or assessment as well as for board certification or maintenance of certification. This study investigates current simulation resources and activities in US otolaryngology residency programs and examines interest in advancing simulation training and assessment within the specialty. Web-based survey. US otolaryngology residency training programs. An electronic web-based survey was disseminated to all US otolaryngology program directors to determine their respective institutional and departmental simulation resources, existing simulation activities, and interest in further simulation initiatives. Descriptive results are reported. Responses were received from 43 of 104 (43%) residency programs. Simulation capabilities and resources are available in most respondents' institutions (78.6% report onsite resources; 73.8% report availability of models, manikins, and devices). Most respondents (61%) report limited simulation activity within otolaryngology. Areas of simulation are broad, addressing technical and nontechnical skills related to clinical training (94%). Simulation is infrequently used for research, credentialing, or systems improvement. The majority of respondents (83.8%) expressed interest in participating in multicenter trials of simulation initiatives. Most respondents from otolaryngology residency programs have incorporated some simulation into their curriculum. Interest among program directors to participate in future multicenter trials appears high. Future research efforts in this area should aim to determine optimal simulators and simulation activities for training and assessment as well as how to best incorporate simulation into otolaryngology residency training programs. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2015.

現象學取向的磨課師教學經驗隱含之意義 Denotations Pertaining to Teaching Experiences of Massive Open Online Courses on the Basis of the Phenomenological Perspective

Directory of Open Access Journals (Sweden)

汪耀華 Yao-Hua Wang

2018-03-01

Full Text Available 本研究旨在探討磨課師（MOOCs）教學經驗隱含之意義。以現象學的深度訪談與資料分析步驟，從受訪教師內隱的心理體驗歷程，歸納屬於人們共通性現象的經驗之意義，可分五大項陳述：傳達以學生為中心的訊息、編導故事情境的教學影片、增加多元學習經驗比小知識重要、放下名利得失心、創新教學的熱情與執行力。綜合上述描述，發現MOOCs授課教師具備五項教學經驗的意義：一、轉化專業實務經驗：將實務歷練注入教材製作，不同於學校課程所教授的內容與型態，讓學生感知有用及興趣。二、善用多媒體建構教材：教師構思教學劇本架構，編導影片或動畫，與生活面連結讓學生易於理解，引導學生想像空間預見未來。三、增加多元學習經驗：引用多元資源教學，安排實務專家參與課程，擴增學生視野及知識。四、精進數位教學知能：放下個人名利心，體驗MOOCs教學，獲得磨練及反思。五、做中學的精神：懷抱創新教學的熱情，勇於嘗試執行。最後，從反思MOOCs授課教師教學經驗的意 義，得到啟示並提出建議。 This study analyzes the denotations pertaining to instructors’ teaching experiences of Massive Open Online Courses (MOOCs. By conducting a detailed phenomenological interview and data analysis, the study provides the denotations pertaining to common human phenomena through intrinsic psychological processes experienced by the instructors. The denotations were described on the basis of five perspectives—Delivering a learner-centered message, editing a teaching video with a story scenario, valuing the diversity of the learning experience over the acquisition of basic knowledge, setting aside fame and profit during teaching, and displaying the power of enthusiastic innovative teaching. On the basis of the five aforementioned descriptions, five

Hysteresis in simulations of malaria transmission

Science.gov (United States)

Yamana, Teresa K.; Qiu, Xin; Eltahir, Elfatih A. B.

2017-10-01

Malaria transmission is a complex system and in many parts of the world is closely related to climate conditions. However, studies on environmental determinants of malaria generally consider only concurrent climate conditions and ignore the historical or initial conditions of the system. Here, we demonstrate the concept of hysteresis in malaria transmission, defined as non-uniqueness of the relationship between malaria prevalence and concurrent climate conditions. We show the dependence of simulated malaria transmission on initial prevalence and the initial level of human immunity in the population. Using realistic time series of environmental variables, we quantify the effect of hysteresis in a modeled population. In a set of numerical experiments using HYDREMATS, a field-tested mechanistic model of malaria transmission, the simulated maximum malaria prevalence depends on both the initial prevalence and the initial level of human immunity in the population. We found the effects of initial conditions to be of comparable magnitude to the effects of interannual variability in environmental conditions in determining malaria prevalence. The memory associated with this hysteresis effect is longer in high transmission settings than in low transmission settings. Our results show that efforts to simulate and forecast malaria transmission must consider the exposure history of a location as well as the concurrent environmental drivers.

Study on the fatigue crack initiation life under spherical contact

Energy Technology Data Exchange (ETDEWEB)

Cho, Yong Joo; Kim, Tae Wan [Busan National Univ., Busan (Korea, Republic of); Lee, Mun Ju [Samsung Electronics Co., Ltd., Suwon (Korea, Republic of)

2001-08-01

In case of contact fatigue, the accurate calculation of surface tractions and subsurface stress is essential to the prediction of crack initiation life. Surface tractions influencing shear stress amplitude have been obtained by contact analysis based on influence function. Subsurface stress has been obtained by using rectangular patch solutions. In this study, to simulate asperity contact under sliding condition, the tip of asperity was simulated by sphere and to calculate crack initiation life in the substrate, dislocation pileup theory was used.

Study on the fatigue crack initiation life under spherical contact

International Nuclear Information System (INIS)

Cho, Yong Joo; Kim, Tae Wan; Lee, Mun Ju

2001-01-01

In case of contact fatigue, the accurate calculation of surface tractions and subsurface stress is essential to the prediction of crack initiation life. Surface tractions influencing shear stress amplitude have been obtained by contact analysis based on influence function. Subsurface stress has been obtained by using rectangular patch solutions. In this study, to simulate asperity contact under sliding condition, the tip of asperity was simulated by sphere and to calculate crack initiation life in the substrate, dislocation pileup theory was used

Should tsunami models use a nonzero initial condition for horizontal velocity?

Science.gov (United States)

Nava, G.; Lotto, G. C.; Dunham, E. M.

2017-12-01

Tsunami propagation in the open ocean is most commonly modeled by solving the shallow water wave equations. These equations require two initial conditions: one on sea surface height and another on depth-averaged horizontal particle velocity or, equivalently, horizontal momentum. While most modelers assume that initial velocity is zero, Y.T. Song and collaborators have argued for nonzero initial velocity, claiming that horizontal displacement of a sloping seafloor imparts significant horizontal momentum to the ocean. They show examples in which this effect increases the resulting tsunami height by a factor of two or more relative to models in which initial velocity is zero. We test this claim with a "full-physics" integrated dynamic rupture and tsunami model that couples the elastic response of the Earth to the linearized acoustic-gravitational response of a compressible ocean with gravity; the model self-consistently accounts for seismic waves in the solid Earth, acoustic waves in the ocean, and tsunamis (with dispersion at short wavelengths). We run several full-physics simulations of subduction zone megathrust ruptures and tsunamis in geometries with a sloping seafloor, using both idealized structures and a more realistic Tohoku structure. Substantial horizontal momentum is imparted to the ocean, but almost all momentum is carried away in the form of ocean acoustic waves. We compare tsunami propagation in each full-physics simulation to that predicted by an equivalent shallow water wave simulation with varying assumptions regarding initial conditions. We find that the initial horizontal velocity conditions proposed by Song and collaborators consistently overestimate the tsunami amplitude and predict an inconsistent wave profile. Finally, we determine tsunami initial conditions that are rigorously consistent with our full-physics simulations by isolating the tsunami waves (from ocean acoustic and seismic waves) at some final time, and backpropagating the tsunami

Effect of temperature on crack initiation in gas formed structures

Energy Technology Data Exchange (ETDEWEB)

Gohari, S.; Vrcelj, Z.; Sharifi, S.; Sharifishourabi, G.; Abadi, R. [Universiti Teknlogi Malaysia, Skudai (Malaysia)

2013-12-15

In the gas forming process, the work piece is formed by applying gas pressure. However, the gas pressure and the accompanying gas temperature can result in crack initiation and unstable crack growth. Thus, it is vital to determine the critical values of applied gas pressure and temperature to avoid crack and fracture failure. We studied the mechanism of fracture using an experimental approach and finite element simulations of a perfect aluminum sheet containing no inclusions and voids. The definition of crack was based on ductile damage mechanics. For inspection of initiation of crack and rupture in gas-metal forming, the ABAQUS/EXPLICIT simulation was used. In gas forming, the applied load is the pressure applied rather than the punching force. The results obtained from both the experimental approach and finite element simulations were compared. The effects of various parameters, such as temperature and gas pressure value on crack initiation, were taken into account.

Reliance on Simulation in Initial Entry Rifle Marksmanship Training and Future Directions for Simulation

Science.gov (United States)

2016-11-01

drills has direct and valuable application to training marksmanship skills, for the novice firers in the assessment, more attention was needed to insure... training in a simulator at real time, actual flight seemed to take place at a much faster time frame. However, pilots reported that after practicing in...who used the EST 2000 (Scholtes & Stapp, 1994), where a concern was raised about less attention paid to weapon safety during EST training than on

Effect of initial perturbation amplitude on Richtmyer-Meshkov flows induced by strong shocks

Energy Technology Data Exchange (ETDEWEB)

Dell, Z.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com, E-mail: sabarji@andrew.cmu.edu [Mellon College of Science and Carnegie Mellon University – Qatar, Carnegie Mellon University, Pittsburgh, Pennsylvania 15231 (United States); Stellingwerf, R. F. [Stellingwerf Consulting, Huntsville, Alabama 35803 (United States)

2015-09-15

We systematically study the effect of the initial perturbation on Richtmyer-Meshkov (RM) flows induced by strong shocks in fluids with contrasting densities. Smooth Particle Hydrodynamics simulations are employed. A broad range of shock strengths and density ratios is considered. The amplitude of the initial single mode sinusoidal perturbation of the interface varies from 0% to 100% of its wavelength. The simulations results are compared, wherever possible, with four rigorous theories, and with other experiments and simulations, achieving good quantitative and qualitative agreement. Our study is focused on early time dynamics of the Richtmyer-Meshkov instability (RMI). We analyze the initial growth-rate of RMI immediately after the shock passage, when the perturbation amplitude increases linearly with time. For the first time, to the authors' knowledge, we find that the initial growth-rate of RMI is a non-monotone function of the initial perturbation amplitude, thus restraining the amount of energy that can be deposited by the shock at the interface. The maximum value of the initial growth-rate depends on the shock strength and the density ratio, whereas the corresponding value of the initial perturbation amplitude depends only slightly on the shock strength and density ratio.

Persistence of Initial Conditions in Continental Scale Air Quality Simulations

Data.gov (United States)

U.S. Environmental Protection Agency — This dataset contains the data used in Figures 1 – 6 and Table 2 of the technical note "Persistence of Initial Conditions in Continental Scale Air Quality...

Products of Ozone-Initiated Chemistry in a Simulated Aircraft Environment

DEFF Research Database (Denmark)

Wisthaler, Armin; Tamás, Gyöngyi; Wyon, David P.

2005-01-01

We used proton-transfer-reaction mass spectrometry (PTR-MS) to examine the products formed when ozone reacted with the materials in a simulated aircraft cabin, including a loaded high-efficiency particulate air (HEPA) filter in the return air system. Four conditions were examined: cabin (baseline...

Sustained qualification process for full scope nuclear power plant simulators

International Nuclear Information System (INIS)

Pirson, J.; Stubbe, E.; Vanhoenacker, L.

1994-01-01

In the past decade, simulator training for all nuclear power plant operators has evolved into a vital requirement. To assure a correct training, the simulator qualification process is an important issue not only for the initial validation but also following major simulator updates, which are necessary during the lifetime of the simulator. In order to avoid degradation of the simulator validated software, the modifications have to be introduced according to a rigorous methodology and a practical requalification process has to be applied. Such methodology has to be enforced at every phase of the simulator construction or updating process from plant data package constitution, over simulator software development to simulator response qualification. The initial qualification and requalification process is based on the 3 levels identified by the ANSI/ANS 3-5 standard for steady-state, operational transients and accident conditions. For the initial certification of the full scope simulators in Belgium, a practical qualification methodology has been applied, which has been adapted into a set of non regression tests for the requalification after major simulator updates. (orig.) (4 refs., 3 figs.)

The Use of Indirect Estimates of Soil Moisture to Initialize Coupled Models and its Impact on Short-Term and Seasonal Simulations

Science.gov (United States)

Lapenta, William M.; Crosson, William; Dembek, Scott; Lakhtakia, Mercedes

1998-01-01

It is well known that soil moisture is a characteristic of the land surface that strongly affects the partitioning of outgoing radiation into sensible and latent heat which significantly impacts both weather and climate. Detailed land surface schemes are now being coupled to mesoscale atmospheric models in order to represent the effect of soil moisture upon atmospheric simulations. However, there is little direct soil moisture data available to initialize these models on regional to continental scales. As a result, a Soil Hydrology Model (SHM) is currently being used to generate an indirect estimate of the soil moisture conditions over the continental United States at a grid resolution of 36 Km on a daily basis since 8 May 1995. The SHM is forced by analyses of atmospheric observations including precipitation and contains detailed information on slope soil and landcover characteristics.The purpose of this paper is to evaluate the utility of initializing a detailed coupled model with the soil moisture data produced by SHM.

Grounding by Attention Simulation in Peripersonal Space: Pupils Dilate to Pinch Grip But Not Big Size Nominal Classifier.

Science.gov (United States)

Lobben, Marit; Bochynska, Agata

2018-03-01

Grammatical categories represent implicit knowledge, and it is not known if such abstract linguistic knowledge can be continuously grounded in real-life experiences, nor is it known what types of mental states can be simulated. A former study showed that attention bias in peripersonal space (PPS) affects reaction times in grammatical congruency judgments of nominal classifiers, suggesting that simulated semantics may include reenactment of attention. In this study, we contrasted a Chinese nominal classifier used with nouns denoting pinch grip objects with a classifier for nouns with big object referents in a pupil dilation experiment. Twenty Chinese native speakers read grammatical and ungrammatical classifier-noun combinations and made grammaticality judgment while their pupillary responses were measured. It was found that their pupils dilated significantly more to the pinch grip classifier than to the big object classifier, indicating attention simulation in PPS. Pupil dilations were also significantly larger with congruent trials on the whole than in incongruent trials, but crucially, congruency and classifier semantics were independent of each other. No such effects were found in controls. Copyright © 2017 Cognitive Science Society, Inc.

Tsunami simulation method initiated from waveforms observed by ocean bottom pressure sensors for real-time tsunami forecast; Applied for 2011 Tohoku Tsunami

Science.gov (United States)

Tanioka, Yuichiro

2017-04-01

After tsunami disaster due to the 2011 Tohoku-oki great earthquake, improvement of the tsunami forecast has been an urgent issue in Japan. National Institute of Disaster Prevention is installing a cable network system of earthquake and tsunami observation (S-NET) at the ocean bottom along the Japan and Kurile trench. This cable system includes 125 pressure sensors (tsunami meters) which are separated by 30 km. Along the Nankai trough, JAMSTEC already installed and operated the cable network system of seismometers and pressure sensors (DONET and DONET2). Those systems are the most dense observation network systems on top of source areas of great underthrust earthquakes in the world. Real-time tsunami forecast has depended on estimation of earthquake parameters, such as epicenter, depth, and magnitude of earthquakes. Recently, tsunami forecast method has been developed using the estimation of tsunami source from tsunami waveforms observed at the ocean bottom pressure sensors. However, when we have many pressure sensors separated by 30km on top of the source area, we do not need to estimate the tsunami source or earthquake source to compute tsunami. Instead, we can initiate a tsunami simulation from those dense tsunami observed data. Observed tsunami height differences with a time interval at the ocean bottom pressure sensors separated by 30 km were used to estimate tsunami height distribution at a particular time. In our new method, tsunami numerical simulation was initiated from those estimated tsunami height distribution. In this paper, the above method is improved and applied for the tsunami generated by the 2011 Tohoku-oki great earthquake. Tsunami source model of the 2011 Tohoku-oki great earthquake estimated using observed tsunami waveforms, coseimic deformation observed by GPS and ocean bottom sensors by Gusman et al. (2012) is used in this study. The ocean surface deformation is computed from the source model and used as an initial condition of tsunami

The MIMIC Method with Scale Purification for Detecting Differential Item Functioning

Science.gov (United States)

Wang, Wen-Chung; Shih, Ching-Lin; Yang, Chih-Chien

2009-01-01

This study implements a scale purification procedure onto the standard MIMIC method for differential item functioning (DIF) detection and assesses its performance through a series of simulations. It is found that the MIMIC method with scale purification (denoted as M-SP) outperforms the standard MIMIC method (denoted as M-ST) in controlling…

Impacts of model initialization on an integrated surface water - groundwater model

KAUST Repository

Ajami, Hoori

2015-04-01

Integrated hydrologic models characterize catchment responses by coupling the subsurface flow with land surface processes. One of the major areas of uncertainty in such models is the specification of the initial condition and its influence on subsequent simulations. A key challenge in model initialization is that it requires spatially distributed information on model states, groundwater levels and soil moisture, even when such data are not routinely available. Here, the impact of uncertainty in initial condition was explored across a 208 km2 catchment in Denmark using the ParFlow.CLM model. The initialization impact was assessed under two meteorological conditions (wet vs dry) using five depth to water table and soil moisture distributions obtained from various equilibrium states (thermal, root zone, discharge, saturated and unsaturated zone equilibrium) during the model spin-up. Each of these equilibrium states correspond to varying computation times to achieve stability in a particular aspect of the system state. Results identified particular sensitivity in modelled recharge and stream flow to the different initializations, but reduced sensitivity in modelled energy fluxes. Analysis also suggests that to simulate a year that is wetter than the spin-up period, an initialization based on discharge equilibrium is adequate to capture the direction and magnitude of surface water–groundwater exchanges. For a drier or hydrologically similar year to the spin-up period, an initialization based on groundwater equilibrium is required. Variability of monthly subsurface storage changes and discharge bias at the scale of a hydrological event show that the initialization impacts do not diminish as the simulations progress, highlighting the importance of robust and accurate initialization in capturing surface water–groundwater dynamics.

Materials Genome Initiative

Science.gov (United States)

Vickers, John

2015-01-01

The Materials Genome Initiative (MGI) project element is a cross-Center effort that is focused on the integration of computational tools to simulate manufacturing processes and materials behavior. These computational simulations will be utilized to gain understanding of processes and materials behavior to accelerate process development and certification to more efficiently integrate new materials in existing NASA projects and to lead to the design of new materials for improved performance. This NASA effort looks to collaborate with efforts at other government agencies and universities working under the national MGI. MGI plans to develop integrated computational/experimental/ processing methodologies for accelerating discovery and insertion of materials to satisfy NASA's unique mission demands. The challenges include validated design tools that incorporate materials properties, processes, and design requirements; and materials process control to rapidly mature emerging manufacturing methods and develop certified manufacturing processes

Modeling of laser damage initiated by surface contamination

International Nuclear Information System (INIS)

Feit, M.D.; Rubenchik, A.M.; Faux, D.R.; Riddle, R.A.; Shapiro, A.; Eder, D.C.; Penetrante, B.M.; Milam, D.; Genin, F.Y.; Kozlowski, M.R.

1996-11-01

The authors are engaged in a comprehensive effort to understand and model the initiation and growth of laser damage initiated by surface contaminants. This includes, for example, the initial absorption by the contaminant, heating and plasma generation, pressure and thermal loading of the transparent substrate, and subsequent shockwave propagation, 'splashing' of molten material and possible spallation, optical propagation and scattering, and treatment of material fracture. The integration use of large radiation hydrodynamics codes, optical propagation codes and material strength codes enables a comprehensive view of the damage process The following picture of surface contaminant initiated laser damage is emerging from our simulations

Criteria for initiation of tokamak disruptions

International Nuclear Information System (INIS)

Hopcraft, K.I.; Turner, M.F.

1986-01-01

The process by which a tokamak plasma evolves from an equilibrium state containing a saturated magnetic island to one which is disruptively unstable is discussed and illustrated by numerical simulation of a resistive magnetoplasma. Those elements which are required to initiate a disruption are delineated

Influence of local crystallographic configuration on microcrack initiation in fatigued 316LN stainless steel: Experiments and crystal plasticity finite elements simulations

Energy Technology Data Exchange (ETDEWEB)

Signor, L., E-mail: loic.signor@ensma.fr [Institut Pprime (UPR3346) CNRS/ISAE-ENSMA/Poitiers University (France); Villechaise, P.; Ghidossi, T.; Lacoste, E.; Gueguen, M. [Institut Pprime (UPR3346) CNRS/ISAE-ENSMA/Poitiers University (France); Courtin, S. [AREVA NP (France)

2016-01-01

Local crystallographic configurations (also referred to as local micro-texture) which promote transgranular micro-crack initiation in 316LN stainless steel in low cycle fatigue are studied. Specimens were subjected to tension-compression with constant plastic strain amplitude, in air, at room temperature, during 5000 cycles (i.e. about 20% of the fatigue life). The first part of this work is devoted to a statistical analysis of slip marks and cracks observed at surface of one fatigued specimen using scanning electron microscope (SEM), in a region composed of about 1000 grains. 95 micro-cracks initiated along persistent slip markings detected in this region are analyzed with respect to different characteristics of grains, especially crystallographic orientation, measured using electron backscatter diffraction (EBSD). From the detailed analysis of the numerous data derived from these observations and measurements performed only at surface, the two main significant factors which are found to favour crack formation are the grain size and the orientation of the activated slip system with respect to the surface. Indeed, the mean size of grains which contain cracks is almost twice the one of the remaining grains. Moreover, for most grains in which cracks are observed, the angle between the normal to the surface and the activated Burgers vector (resp. the normal to the activated slip plane) lies in the range [30°, 50°] (resp. [55°, 70°]). No other characteristic was found to provide significant and direct information in order to identify initiation sites. Thus, in the second part of this work, the analysis of initiation sites is performed using additional information relative to three-dimensional (3D) aspects of the microstructure. 3D characterisation of the polycrystalline microstructure and some cracks in one fatigued specimen was achieved using serial-sectioning technique combined with SEM and EBSD. As an example, the study of one specific crack and its surrounding

IPCC AR4 Simulations

Indian Academy of Sciences (India)

Future climate simulations (initial conditions from end of the 20th Century simulation):. “Committed Climate Change”: hold concentrations at year 2000; SRES A2 to 2100; SRES A1B to 2100 then fix concentrations (~720 ppm) for an additional century (with one realization extended to 2300); As above but with SRES B1 ...

Initial Conditions Corresponding to Optimal Ion Acceleration in the VINCY Cyclotron

International Nuclear Information System (INIS)

Ilic, A. Z.; Ristic-Djurovic, J. L.; Cirkovic, S. T.

2007-01-01

The quality of a beam in a cyclotron depends a lot on the choice of initial conditions for acceleration. The criteria defining optimal acceleration as well as the choice of the corresponding initial conditions have been outlined. The results of beam dynamics simulations with optimal and non-optimal initial conditions are compared. (author)

Initial conditions of radiative shock experiments

International Nuclear Information System (INIS)

Kuranz, C. C.; Drake, R. P.; Krauland, C. M.; Marion, D. C.; Grosskopf, M. J.; Rutter, E.; Torralva, B.; Holloway, J. P.; Bingham, D.; Goh, J.; Boehly, T. R.; Sorce, A. T.

2013-01-01

We performed experiments at the Omega Laser Facility to characterize the initial, laser-driven state of a radiative shock experiment. These experiments aimed to measure the shock breakout time from a thin, laser-irradiated Be disk. The data are then used to inform a range of valid model parameters, such as electron flux limiter and polytropic γ, used when simulating radiative shock experiments using radiation hydrodynamics codes. The characterization experiment and the radiative shock experiment use a laser irradiance of ∼7 × 10 14 W cm −2 to launch a shock in the Be disk. A velocity interferometer and a streaked optical pyrometer were used to infer the amount of time for the shock to move through the Be disk. The experimental results were compared with simulation results from the Hyades code, which can be used to model the initial conditions of a radiative shock system using the CRASH code

Simulation and initial experiments of a high power pulsed TEA CO2 laser

Science.gov (United States)

Torabi, R.; Saghafifar, H.; Koushki, A. M.; Ganjovi, A. A.

2016-01-01

In this paper, the output characteristics of a UV pin array pre-ionized TEA CO2 laser have been simulated and compared with the associated experimental data. In our simulation, a new theoretical model has been improved for transient behavior analysis of the discharge current pulse. The laser discharge tube was modeled by a nonlinear RLC electric circuit as a real model for electron density calculation. This model was coupled with a six-temperature model (6TM) in order to simulation dynamic emission processes of the TEA CO2 laser. The equations were solved numerically by the fourth order Runge-Kutta numerical method and some important variables such as current and voltage of the main discharge, resistance of the plasma column and electron density in the main discharge region, were calculated as functions of time. The effects of non-dissociation factor, rotational quantum number and output coupler reflectivity were also studied theoretically. The experimental and simulation results are in good agreement.

Utilization of NPP Krsko plant specific simulator

International Nuclear Information System (INIS)

Fifnja, I.; Pribozic, F.; Krajnc, J.

2002-01-01

NPP Krsko started with licensed operator training using its own plant-specific full scope simulator in April 2000. Today, two years after simulator was completed, the benefits of simulator use are visible in various fields. The simulator was effectively used to conduct licensed operator continuing training and practical examinations. Two-year continuous training program was designed to help maintain and improve operator performance. The simulator was also used to provide just-in-time training prior to plant evolutions. Together with licensed operators the non-licensed operators are also included into simulator training to provide affective team training opportunity and to foster good communication and increase scenario realism. Now, the first group of initial licensed operator training using plant-specific simulator is also almost completed. It is the first time that NPP Krsko training department conducted complete initial training and this will represent the great experience for future training. Besides training, the simulator was also utilized for procedure development and validation, operating standards development, testing of plant modifications and other activities, like emergency preparedness procedures validation and training exercises.(author)

OISI dynamic end-to-end modeling tool

Science.gov (United States)

Kersten, Michael; Weidler, Alexander; Wilhelm, Rainer; Johann, Ulrich A.; Szerdahelyi, Laszlo

2000-07-01

The OISI Dynamic end-to-end modeling tool is tailored to end-to-end modeling and dynamic simulation of Earth- and space-based actively controlled optical instruments such as e.g. optical stellar interferometers. `End-to-end modeling' is meant to denote the feature that the overall model comprises besides optical sub-models also structural, sensor, actuator, controller and disturbance sub-models influencing the optical transmission, so that the system- level instrument performance due to disturbances and active optics can be simulated. This tool has been developed to support performance analysis and prediction as well as control loop design and fine-tuning for OISI, Germany's preparatory program for optical/infrared spaceborne interferometry initiated in 1994 by Dornier Satellitensysteme GmbH in Friedrichshafen.

The Initial Conditions of Fractional Calculus

International Nuclear Information System (INIS)

Trigeassou, J. C.; Maamri, N.

2011-01-01

During the past fifty years , Fractional Calculus has become an original and renowned mathematical tool for the modelling of diffusion Partial Differential Equations and the design of robust control algorithms. However, in spite of these celebrated results, some theoretical problems have not yet received a satisfying solution. The mastery of initial conditions, either for Fractional Differential Equations (FDEs) or for the Caputo and Riemann-Liouville fractional derivatives, remains an open research domain. The solution of this fundamental problem, also related to the long range memory property, is certainly the necessary prerequisite for a satisfying approach to modelling and control applications. The fractional integrator and its continuously frequency distributed differential model is a valuable tool for the simulation of fractional systems and the solution of initial condition problems. Indeed, the infinite dimensional state vector of fractional integrators allows the direct generalization to fractional calculus of the theoretical results of integer order systems. After a reminder of definitions and properties related to fractional derivatives and systems, this presentation is intended to show, based on the results of two recent publications [1,2], how the fractional integrator provides the solution of the initial condition problem of FDEs and of Caputo and Riemann-Liouville fractional derivatives. Numerical simulation examples illustrate and validate these new theoretical concepts.

Research on Initiation Sensitivity of Solid Explosive and Planer Initiation System

Directory of Open Access Journals (Sweden)

N Matsuo

2016-09-01

Full Text Available Firstly, recently, there are a lot of techniques being demanded for complex process, various explosive initiation method and highly accurate control of detonation are needed. In this research, the metal foil explosion using high current is focused attention on the method to obtain linear or planate initiation easily, and the main evaluation of metal foil explosion to initiate explosive was conducted. The explosion power was evaluated by observing optically the underwater shock wave generated from the metal foil explosion. Secondly, in high energy explosive processing, there are several applications, such as shock compaction, explosive welding, food processing and explosive forming. In these explosive applications, a high sensitive explosive has been mainly used. The high sensitive explosive is so dangerous, since it can lead to explosion suddenly. So, for developing explosives, the safety is the most important thing as well as low manufacturing cost and explosive characteristics. In this work, we have focused on the initiation sensitivity of a solid explosive and performed numerical analysis of sympathetic detonation. The numerical analysis is calculated by LS-DYNA 3D (commercial code. To understand the initiation reaction of an explosive, Lee-Tarver equation was used and impact detonation process was analyzed by ALE code. Configuration of simulation model is a quarter of circular cylinder. The donor type of explosive (SEP was used as initiation explosive. When the donor explosive is exploded, a shock wave is generated and it propagates into PMMA, air and metallic layers in order. During passing through the layers, the shock wave is attenuated and finally, it has influence on the acceptor explosive, Comp. B. Here, we evaluate the initiation of acceptor explosive and discuss about detonation pressure, reactive rate of acceptor explosive and attenuation of impact pressure.

The morphological evolution and internal convection of ExB-drifting plasma clouds: Theory, dielectric-in-cell simulations, and N-body dielectric simulations

International Nuclear Information System (INIS)

Borovsky, J.E.; Hansen, P.J.

1998-01-01

The evolution of ExB-drifting plasma clouds is investigated with the aid of a computational technique denoted here as open-quotes dielectric-in-cell.close quotes Many of the familiar phenomena associated with clouds of collisionless plasma are seen and explained and less-well-known phenomena associated with convection patterns, with the stripping of cloud material, and with the evolution of plasma clouds composed of differing ion species are investigated. The effects of spatially uniform diffusion are studied with the dielectric-in-cell technique and with another computational technique denoted as open-quotes N-body dielectric;close quotes the suppression of convection, the suppression of structure growth, the increase in material stripping, and the evolution of cloud anisotropy are examined. copyright 1998 American Institute of Physics

Impacts of initial convective structure on subsequent squall line evolution

Science.gov (United States)

Varble, A.; Morrison, H.; Zipser, E. J.

2017-12-01

A Weather Research and Forecasting simulation of the 20 May 2011 MC3E squall line using 750-m horizontal grid spacing produces wide convective regions with strongly upshear tilted convective updrafts and mesoscale bowing segments that are not produced in radar observations. Similar features occur across several different bulk microphysics schemes, despite surface observations exhibiting cold pool equivalent potential temperature drops that are similar to and pressure rises that are greater than those in the simulation. Observed rear inflow remains more elevated than simulated, partly counteracting the cold pool circulation, whereas the simulated rear inflow descends to low levels, maintaining its strength and reinforcing the cold pool circulation that overpowers the pre-squall line low level vertical wind shear. The descent and strength of the simulated rear inflow is fueled by strong latent cooling caused by large ice water contents detrained from upshear tilted convective cores that accumulate at the rear of the stratiform region. This simulated squall evolution is sensitive to model resolution, which is too coarse to resolve individual convective drafts. Nesting a 250-m horizontal grid spacing domain into the 750-m domain substantially alters the initial convective cells with reduced latent cooling, weaker convective downdrafts, and a weaker initial cold pool. As the initial convective cells develop into a squall line, the rear inflow remains more elevated in the 250-m domain with a cold pool that eventually develops to be just as strong and deeper than the one in the 750-m run. Despite this, the convective cores remain more upright in the 250-m run with the rear inflow partly counteracting the cold pool circulation, whereas the 750-m rear inflow near the surface reinforces the shallower cold pool and causes bowing in the squall line. The different structure in the 750-m run produces excessive mid-level front-to-rear detrainment that widens the convective region

Initial porosity of random packing : Computer simulation of grain rearrangement

NARCIS (Netherlands)

Alberts, L.J.H.

2005-01-01

The initial porosity of clastic sediments is poorly defined. In spite of this, it is an important parameter in many models that describe the diagenetic processes taking place during the burial of sediments and which are responsible for the transition from sand to sandstone. Diagenetic models are of

Assigning Robust Default Values in Building Performance Simulation Software for Improved Decision-Making in the Initial Stages of Building Design.

Science.gov (United States)

Hiyama, Kyosuke

2015-01-01

Applying data mining techniques on a database of BIM models could provide valuable insights in key design patterns implicitly present in these BIM models. The architectural designer would then be able to use previous data from existing building projects as default values in building performance simulation software for the early phases of building design. The author has proposed the method to minimize the magnitude of the variation in these default values in subsequent design stages. This approach maintains the accuracy of the simulation results in the initial stages of building design. In this study, a more convincing argument is presented to demonstrate the significance of the new method. The variation in the ideal default values for different building design conditions is assessed first. Next, the influence of each condition on these variations is investigated. The space depth is found to have a large impact on the ideal default value of the window to wall ratio. In addition, the presence or absence of lighting control and natural ventilation has a significant influence on the ideal default value. These effects can be used to identify the types of building conditions that should be considered to determine the ideal default values.

Parameter estimation of a three-axis spacecraft simulator using recursive least-squares approach with tracking differentiator and Extended Kalman Filter

Science.gov (United States)

Xu, Zheyao; Qi, Naiming; Chen, Yukun

2015-12-01

Spacecraft simulators are widely used to study the dynamics, guidance, navigation, and control of a spacecraft on the ground. A spacecraft simulator can have three rotational degrees of freedom by using a spherical air-bearing to simulate a frictionless and micro-gravity space environment. The moment of inertia and center of mass are essential for control system design of ground-based three-axis spacecraft simulators. Unfortunately, they cannot be known precisely. This paper presents two approaches, i.e. a recursive least-squares (RLS) approach with tracking differentiator (TD) and Extended Kalman Filter (EKF) method, to estimate inertia parameters. The tracking differentiator (TD) filter the noise coupled with the measured signals and generate derivate of the measured signals. Combination of two TD filters in series obtains the angular accelerations that are required in RLS (TD-TD-RLS). Another method that does not need to estimate the angular accelerations is using the integrated form of dynamics equation. An extended TD (ETD) filter which can also generate the integration of the function of signals is presented for RLS (denoted as ETD-RLS). States and inertia parameters are estimated simultaneously using EKF. The observability is analyzed. All proposed methods are illustrated by simulations and experiments.

Aerodynamic Simulation of Indoor Flight

Science.gov (United States)

De Leon, Nelson; De Leon, Matthew N.

2007-01-01

We develop a two-dimensional flight simulator for lightweight (less than 10 g) indoor planes. The simulator consists of four coupled time differential equations describing the plane CG, plane pitch and motor. The equations are integrated numerically with appropriate parameters and initial conditions for two planes: (1) Science Olympiad and (2)…

Magnetohydrodynamic Modeling of Solar Coronal Dynamics with an Initial Non-force-free Magnetic Field

Energy Technology Data Exchange (ETDEWEB)

Prasad, A.; Bhattacharyya, R.; Kumar, Sanjay [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)

2017-05-01

The magnetic fields in the solar corona are generally neither force-free nor axisymmetric and have complex dynamics that are difficult to characterize. Here we simulate the topological evolution of solar coronal magnetic field lines (MFLs) using a magnetohydrodynamic model. The simulation is initialized with a non-axisymmetric non-force-free magnetic field that best correlates with the observed vector magnetograms of solar active regions (ARs). To focus on these ideas, simulations are performed for the flaring AR 11283 noted for its complexity and well-documented dynamics. The simulated dynamics develops as the initial Lorentz force pushes the plasma and facilitates successive magnetic reconnections at the two X-type null lines present in the initial field. Importantly, the simulation allows for the spontaneous development of mass flow, unique among contemporary works, that preferentially reconnects field lines at one of the X-type null lines. Consequently, a flux rope consisting of low-lying twisted MFLs, which approximately traces the major polarity inversion line, undergoes an asymmetric monotonic rise. The rise is attributed to a reduction in the magnetic tension force at the region overlying the rope, resulting from the reconnection. A monotonic rise of the rope is in conformity with the standard scenario of flares. Importantly, the simulated dynamics leads to bifurcations of the flux rope, which, being akin to the observed filament bifurcation in AR 11283, establishes the appropriateness of the initial field in describing ARs.

Initially curved microplates under electrostatic actuation: theory and experiment

KAUST Repository

Saghir, Shahid

2016-07-01

Microplates are the building blocks of many micro-electro-mechanical systems. It is common for them to experience initial curvature imperfection due to residual stresses caused by the micro fabrication process. Such plates are essentially different from perfectly flat ones and cannot be modeled using flat plate models. In this paper, we adopt a dynamic analog of the von Karman governing equations of imperfect plates. These equations are then used to develop a reduced order model based on the Galerkin procedure, to simulate the static and dynamic behavior of the microplate under electrostatic actuation. To validate the simulation results, an initially curved imperfect microplate made of silicon nitride is fabricated and tested. The static behaviour of the microplate is investigated when applying a DC voltage Vdc. Then, the dynamic behaviour of the microplate is examined under the application of a harmonic AC voltage, Vac, superimposed to Vdc. The simulation results show good agreement with the experimentally measured responses. © 2016 IOP Publishing Ltd.

Electron and ion heating by whistler turbulence: Three-dimensional particle-in-cell simulations

International Nuclear Information System (INIS)

Hughes, R. Scott; Gary, S. Peter; Wang, Joseph

2014-01-01

Three-dimensional particle-in-cell simulations of decaying whistler turbulence are carried out on a collisionless, homogeneous, magnetized, electron-ion plasma model. In addition, the simulations use an initial ensemble of relatively long wavelength whistler modes with a broad range of initial propagation directions with an initial electron beta β e = 0.05. The computations follow the temporal evolution of the fluctuations as they cascade into broadband turbulent spectra at shorter wavelengths. Three simulations correspond to successively larger simulation boxes and successively longer wavelengths of the initial fluctuations. The computations confirm previous results showing electron heating is preferentially parallel to the background magnetic field B o , and ion heating is preferentially perpendicular to B o . The new results here are that larger simulation boxes and longer initial whistler wavelengths yield weaker overall dissipation, consistent with linear dispersion theory predictions of decreased damping, stronger ion heating, consistent with a stronger ion Landau resonance, and weaker electron heating

Analysis of Customer Behaviour and Online Retailers Strategies Using the Agent-Based Simulation

Directory of Open Access Journals (Sweden)

Sava Čavoški

2015-02-01

Full Text Available This paper discusses the application of ABMS – agent-based modelling and simulation in the analysis of customer behaviour on B2C e-commerce websites as well as in the analysis of various business decisions upon the effects of on-line sales. By linking the areas of modelling based on agents and electronic commerce, this paper addresses the new opportunities for a quality assessment of consumer behaviour and reasons explaining this behaviour in e-commerce. The interactions of agents that make up this model are sublimated in the utility function that provides the basis for decision-making in the model. The rules of behaviour and interactions, included in the model through the utility function, denote the complexity of the decision-making process which occurs in evaluation and purchase of products in the part of B2C e-commerce. The simulation model implemented in the software NetLogo enables the monitoring of all interactions between the consumers (ConsumerAgents, seller-Internet sites (SellerAgents and advertisement agents (BannerAgents by generating the indicators of B2C site business performance.

[Simulation as possible training for palliative emergencies: prospective initial data analysis of participants from two simulation training sessions].

Science.gov (United States)

Wiese, C H R; Bosse, G; Schröder, T; Lassen, C L; Bundscherer, A C; Graf, B M; Zausig, Y A

2015-01-01

Palliative emergencies describe an acute situation in patients with a life-limiting illness. At present defined curricula for prehospital emergency physician training for palliative emergencies are limited. Simulation-based training (SBT) for such palliative emergency situations is an exception both nationally and internationally. This article presents the preparation of recommendations in the training and development of palliative care emergency situations. A selected literature search was performed using PubMed, EMBASE, Medline and the Cochrane database (1990-2013). Reference lists of included articles were checked by two reviewers. Data of the included articles were extracted, evaluated und summarized. In the second phase the participants of two simulated scenarios of palliative emergencies were asked to complete an anonymous 15-item questionnaire. The results of the literature search and the questionnaire-based investigation were compared and recommendations were formulated based on the results. Altogether 30 eligible national and international articles were included. Overall, training curricula in palliative emergencies are currently being developed nationally and internationally but are not yet widely integrated into emergency medical training and education. In the second part of the investigation, 25 participants (9 male, 16 female, 20 physicians and 5 nurses) were included in 4 multiprofessional emergency medical simulation training sessions. The most important interests of the participants were the problems for training and further education concerning palliative emergencies described in the national and international literature. The literature review and the expectations of the participants underlined that the development and characteristics of palliative emergencies will become increasingly more important in outpatient emergency medicine. All participants considered palliative care to be very important concerning the competency for end-of-life decisions

The validity of multiphase DNS initialized on the basis of single--point statistics

Science.gov (United States)

Subramaniam, Shankar

1999-11-01

A study of the point--process statistical representation of a spray reveals that single--point statistical information contained in the droplet distribution function (ddf) is related to a sequence of single surrogate--droplet pdf's, which are in general different from the physical single--droplet pdf's. The results of this study have important consequences for the initialization and evolution of direct numerical simulations (DNS) of multiphase flows, which are usually initialized on the basis of single--point statistics such as the average number density in physical space. If multiphase DNS are initialized in this way, this implies that even the initial representation contains certain implicit assumptions concerning the complete ensemble of realizations, which are invalid for general multiphase flows. Also the evolution of a DNS initialized in this manner is shown to be valid only if an as yet unproven commutation hypothesis holds true. Therefore, it is questionable to what extent DNS that are initialized in this manner constitute a direct simulation of the physical droplets.

Truncated Conjugate Gradient: An Optimal Strategy for the Analytical Evaluation of the Many-Body Polarization Energy and Forces in Molecular Simulations.

Science.gov (United States)

Aviat, Félix; Levitt, Antoine; Stamm, Benjamin; Maday, Yvon; Ren, Pengyu; Ponder, Jay W; Lagardère, Louis; Piquemal, Jean-Philip

2017-01-10

We introduce a new class of methods, denoted as Truncated Conjugate Gradient(TCG), to solve the many-body polarization energy and its associated forces in molecular simulations (i.e. molecular dynamics (MD) and Monte Carlo). The method consists in a fixed number of Conjugate Gradient (CG) iterations. TCG approaches provide a scalable solution to the polarization problem at a user-chosen cost and a corresponding optimal accuracy. The optimality of the CG-method guarantees that the number of the required matrix-vector products are reduced to a minimum compared to other iterative methods. This family of methods is non-empirical, fully adaptive, and provides analytical gradients, avoiding therefore any energy drift in MD as compared to popular iterative solvers. Besides speed, one great advantage of this class of approximate methods is that their accuracy is systematically improvable. Indeed, as the CG-method is a Krylov subspace method, the associated error is monotonically reduced at each iteration. On top of that, two improvements can be proposed at virtually no cost: (i) the use of preconditioners can be employed, which leads to the Truncated Preconditioned Conjugate Gradient (TPCG); (ii) since the residual of the final step of the CG-method is available, one additional Picard fixed point iteration ("peek"), equivalent to one step of Jacobi Over Relaxation (JOR) with relaxation parameter ω, can be made at almost no cost. This method is denoted by TCG-n(ω). Black-box adaptive methods to find good choices of ω are provided and discussed. Results show that TPCG-3(ω) is converged to high accuracy (a few kcal/mol) for various types of systems including proteins and highly charged systems at the fixed cost of four matrix-vector products: three CG iterations plus the initial CG descent direction. Alternatively, T(P)CG-2(ω) provides robust results at a reduced cost (three matrix-vector products) and offers new perspectives for long polarizable MD as a production

An Initial Implementation of Multiagent Simulation of Travel Behavior for a Medium-Sized City in China

Directory of Open Access Journals (Sweden)

Chengxiang Zhuge

2014-01-01

Full Text Available Since the traditional four-step model is so simple that it cannot solve complex modern transportation problems, microsimulation is gradually applied for transportation planning and some researches indicate that it is more compatible and realistic. In this paper, a framework of agent-based simulation of travel behavior is proposed, which is realized by MATSim, a simulation tool developed for large-scale agent-based simulation. MATSim is currently developed and some of its models are under training, so a detailed introduction of simulation structure and preparation of input data will be presented. In practice, the preparation process differs from one to another in different simulation projects because the available data for simulation is various. Thus, a simulation of travel behavior under a condition of limited available survey data will be studied based on MATSim; furthermore, a medium-sized city in China will be taken as an example to check whether agent-based simulation of travel behavior can be successfully applied in China.

Elliptic flow from non-equilibrium initial condition with a saturation scale

International Nuclear Information System (INIS)

Ruggieri, M.; Scardina, F.; Plumari, S.; Greco, V.

2013-01-01

A current goal of relativistic heavy-ion collisions experiments is the search for a Color Glass Condensate (CGC) as the limiting state of QCD matter at very high density. In viscous hydrodynamics simulations, a standard Glauber initial condition leads to estimate 4πη/s∼1, while employing the Kharzeev–Levin–Nardi (KLN) modeling of the glasma leads to at least a factor of 2 larger η/s. Within a kinetic theory approach based on a relativistic Boltzmann-like transport simulation, our main result is that the out-of-equilibrium initial distribution reduces the efficiency in building-up the elliptic flow. At RHIC energy we find the available data on v 2 are in agreement with a 4πη/s∼1 also for KLN initial conditions. More generally, our study shows that the initial non-equilibrium in p-space can have a significant impact on the build-up of anisotropic flow

Factors controlling the initiation of Snowball Earth events

Science.gov (United States)

Voigt, A.

2012-12-01

During the Neoproterozoic glaciations tropical continents were covered by active glaciers that extended down to sea level. To explain these glaciers, the Snowball Earth hypothesis assumes that oceans were completely sea-ice covered during these glaciation, but there is an ongoing debate whether or not some regions of the tropical oceans remained open. In this talk, I will describe past and ongoing climate modelling activities with the comprehensive coupled climate model ECHAM5/MPI-OM that identify and compare factors that control the initiation of Snowball Earth events. I first show that shifting the continents from their present-day location to their Marinoan (635 My BP) low-latitude location increases the planetary albedo, cools the climate, and thereby allows Snowball Earth initiation at higher levels of total solar irradiance and atmospheric CO2. I then present simulations with successively lowered bare sea-ice albedo, disabled sea-ice dynamics, and switched-off ocean heat transport. These simulations show that both lowering the bare sea-ice albedo and disabling sea-ice dynamics increase the critical sea-ice cover in ECHAM5/MPI-OM, but sea-ice dynamics due to strong equatorward sea-ice transport have a much larger influence on the critical CO2. Disabling sea-ice transport allows a state with sea-ice margin at 10 deg latitude by virtue of the Jormungand mechanism. The accumulation of snow on land, in combination with tropical land temperatures below or close to freezing, suggests that tropical land glaciers could easily form in such a state. However, in contrast to aquaplanet simulations without ocean heat transport, there is no sign of a Jormungand hysteresis in the coupled simulations. Ocean heat transport is not responsible for the lack of a Jormungand hysteresis in the coupled simulations. By relating the above findings to previous studies, I will outline promising future avenues of research on the initiation of Snowball Earth events. In particular, an

Assigning Robust Default Values in Building Performance Simulation Software for Improved Decision-Making in the Initial Stages of Building Design

Directory of Open Access Journals (Sweden)

Kyosuke Hiyama

2015-01-01

Full Text Available Applying data mining techniques on a database of BIM models could provide valuable insights in key design patterns implicitly present in these BIM models. The architectural designer would then be able to use previous data from existing building projects as default values in building performance simulation software for the early phases of building design. The author has proposed the method to minimize the magnitude of the variation in these default values in subsequent design stages. This approach maintains the accuracy of the simulation results in the initial stages of building design. In this study, a more convincing argument is presented to demonstrate the significance of the new method. The variation in the ideal default values for different building design conditions is assessed first. Next, the influence of each condition on these variations is investigated. The space depth is found to have a large impact on the ideal default value of the window to wall ratio. In addition, the presence or absence of lighting control and natural ventilation has a significant influence on the ideal default value. These effects can be used to identify the types of building conditions that should be considered to determine the ideal default values.

Microbial Enhanced Oil Recovery - Advanced Reservoir Simulation

DEFF Research Database (Denmark)

Nielsen, Sidsel Marie

the water phase. The biofilm formation implies that the concentration of bacteria near the inlet increases. In combination with surfactant production, the biofilm results in a higher surfactant concentration in the initial part of the reservoir. The oil that is initially bypassed in connection...... simulator. In the streamline simulator, the effect of gravity is introduced using an operator splitting technique. The gravity effect stabilizes oil displacement causing markedly improvement of the oil recovery, when the oil density becomes relatively low. The general characteristics found for MEOR in one......-dimensional simulations are also demonstrated both in two and three dimensions. Overall, this MEOR process conducted in a heterogeneous reservoir also produces more oil compared to waterflooding, when the simulations are run in multiple dimensions. The work presented in this thesis has resulted in two publications so far....

Program of in-pile IASCC testing under the simulated actual plant condition. Development of technique for in-pile IASCC initiation test in JMTR

International Nuclear Information System (INIS)

Ugachi, Hirokazu; Tsukada, Takashi; Kaji, Yoshiyuki; Nagata, Nobuaki; Dozaki, Koji; Takiguchi, Hideki

2003-01-01

Irradiation assisted stress corrosion cracking (IASCC) is caused by the synergistic effects of neutron irradiation, stress and corrosion by high temperature water. It is, therefore, essential to perform in-pile SCC tests, which are material tests under the conditions simulating those of actual LWR operation, in order to clarify the precise mechanism of the phenomenon, though mainly out-of-pile SCC tests for irradiated materials have been carried out in this research field. There are, however, many difficulties to perform in-pile SCC tests. Performing in-pile SCC tests, essential key techniques must be developed. Hence as a part of development of the key techniques for in-pile SCC tests, we have embarked on development of the test technique which enables us to obtain the information concerning the effect of such parameters as applied stress level, water chemistry, irradiation conditions, etc. on the crack initiation behavior. Although it is difficult to detect the crack initiation in in-pile SCC tests, the crack initiation can be evaluated by the detection of specimen rupture if the cross section area of the specimen is small enough. Therefore, we adopted the uniaxial constant loading (UCL) test with small tensile specimens. This paper will describe the current status of the development of several techniques for in-pile SCC initiation tests in JMTR and the results of the performance tests of the designed testing unit using the out-of-pile loop facility. (author)

Simulation model of an electrohydraulic-actuated double-clutch transmission vehicle: modelling and system design

Science.gov (United States)

Schoeftner, J.; Ebner, W.

2017-12-01

Automated and manual transmissions are the main link between engine and powertrain. The technical term when the transmission provides the desired torque during all possible driving conditions is denoted as powertrain matching. Recent developments in the last years show that double-clutch-transmissions (DCTs) are a reasonable compromise in terms of production costs, shifting quality, drivability and fuel efficiency. They have several advantages compared to other automatic transmissions (AT). Most DCTs nowadays consist of a hydraulic actuation control unit, which controls the clutches of the gearbox in order to induce a desired drivetrain torque into the driveline. The main functions of hydraulic systems are manifold: they initiate gear shifts, they provide sufficient oil for lubrication and they control the shift quality by suitably providing a desired oil flow or pressure for the clutch actuation. In this paper, a mathematical model of a passenger car equipped with a DCT is presented. The objective of this contribution is to get an increased understanding for the dynamics of the hydraulic circuit and its coupling to the vehicle drivetrain. The simulation model consists of a hydraulic and a mechanical domain: the hydraulic actuation circuit is described by nonlinear differential equations and includes the dynamics of the line pressure and the proportional valve, as well as the influence of the pressure reducing valve, pipe resistances and accumulator dynamics. The drivetrain with its gear ratios, moments of inertia, torsional stiffness of the rotating shafts and a simple longitudinal vehicle model represent the mechanical domain. The link between hydraulic and mechanical domain is given by the clutch, which combines hydraulic equations and Newton's laws. The presented mathematical model may not only be used as a simulation model for developing the transmission control software, it may also serve as a virtual layout for the design process phase. At the end of this

Equilibrium initial data for moving puncture simulations: the stationary 1 + log slicing

International Nuclear Information System (INIS)

Baumgarte, T W; Matera, K; Etienne, Z B; Liu, Y T; Shapiro, S L; Taniguchi, K; Murchadha, N O

2009-01-01

We discuss a 'stationary 1 + log' slicing condition for the construction of solutions to Einstein's constraint equations. For stationary spacetimes, these initial data give a stationary foliation when evolved with 'moving puncture' gauge conditions that are often used in black hole evolutions. The resulting slicing is time independent and agrees with the slicing generated by being dragged along a timelike Killing vector of the spacetime. When these initial data are evolved with moving puncture gauge conditions, numerical errors arising from coordinate evolution should be minimized. While these properties appear very promising, suggesting that this slicing condition should be an attractive alternative to, for example, maximal slicing, we demonstrate in this paper that solutions can be constructed only for a small class of problems. For binary black hole initial data, in particular, it is often assumed that there exists an approximate helical Killing vector that generates the binary's orbit. We show that 1 + log slices that are stationary with respect to such a helical Killing vector cannot be asymptotically flat, unless the spacetime possesses an additional axial Killing vector.

Closing Symposium of the German Research Initiative ComFliTe

CERN Document Server

Radespiel, Rolf; Burg, Jan; Sørensen, Kaare

2013-01-01

This book reports on the German research initiative ComFliTe (Computational Flight Testing), the main goal of which was to enhance the capabilities of and tools for numerical simulation in flight physics to support future aircraft design and development. The initiative was coordinated by the German Aerospace Center (DLR) and promoted collaboration between the aircraft industry and academia. Activities focused on improving physical modeling for separated flows, developing advanced numerical algorithms for series computations and sensitivity predictions, as well as surrogate and reduced order modeling for aero data production and developing robust fluid-, structure- and flight mechanics coupling procedures. Further topics included more efficient handling of aircraft control surfaces and improving simulation methods for maneuvers, such as gust encounter. The important results of this three-year initiative were presented during the ComFliTe closing symposium, which took place at the DLR in Braunschweig, Germany, ...

Reaction-diffusion fronts with inhomogeneous initial conditions

Energy Technology Data Exchange (ETDEWEB)

Bena, I [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Droz, M [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Martens, K [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Racz, Z [Institute for Theoretical Physics, Eoetvoes University, 1117 Budapest (Hungary)

2007-02-14

Properties of reaction zones resulting from A+B {yields} C type reaction-diffusion processes are investigated by analytical and numerical methods. The reagents A and B are separated initially and, in addition, there is an initial macroscopic inhomogeneity in the distribution of the B species. For simple two-dimensional geometries, exact analytical results are presented for the time evolution of the geometric shape of the front. We also show using cellular automata simulations that the fluctuations can be neglected both in the shape and in the width of the front.

Simulation of aperiodic bipedal sprinting.

Science.gov (United States)

Celik, Huseyin; Piazza, Stephen J

2013-08-01

Synthesis of legged locomotion through dynamic simulation is useful for exploration of the mechanical and control variables that contribute to efficient gait. Most previous simulations have made use of periodicity constraints, a sensible choice for investigations of steady-state walking or running. Sprinting from rest, however, is aperiodic by nature and this aperiodicity is central to the goal of the movement, as performance is determined in large part by a rapid acceleration phase early in the race. The purpose of this study was to create a novel simulation of aperiodic sprinting using a modified spring-loaded inverted pendulum (SLIP) biped model. The optimal control problem was to find the set of controls that minimized the time for the model to run 20 m, and this problem was solved using a direct multiple shooting algorithm that converts the original continuous time problem into piecewise discrete subproblems. The resulting nonlinear programming problem was solved iteratively using a sequential quadratic programming method. The starting point for the optimizer was an initial guess simulation that was a slow alternating-gait "jogging" simulation developed using proportional-derivative feedback to control trunk attitude, swing leg angle, and leg retraction and extension. The optimized aperiodic sprint simulation solution yielded a substantial improvement in locomotion time over the initial guess (2.79 s versus 6.64 s). Following optimization, the model produced forward impulses at the start of the sprint that were four times greater than those of the initial guess simulation, producing more rapid acceleration. Several gait features demonstrated in the optimized sprint simulation correspond to behaviors of human sprinters: forward trunk lean at the start; straightening of the trunk during acceleration; and a dive at the finish. Optimization resulted in reduced foot contact times (0.065 s versus 0.210 s), but contact times early in the optimized

Real time simulation techniques in Taiwan - Maanshan compact simulator

International Nuclear Information System (INIS)

Liang, K.-S.; Chuang, Y.-M.; Ko, H.-T.

2004-01-01

Recognizing the demand and potential market of simulators in various industries, a special project for real time simulation technology transfer was initiated in Taiwan in 1991. In this technology transfer program, the most advanced real-time dynamic modules for nuclear power simulation were introduced. Those modules can be divided into two categories; one is modeling related to catch dynamic response of each system, and the other is computer related to provide special real time computing environment and man-machine interface. The modeling related modules consist of the thermodynamic module, the three-dimensional core neutronics module and the advanced balance of plant module. As planned in the project, the technology transfer team should build a compact simulator for the Maanshan power plant before the end of the project to demonstrate the success of the technology transfer program. The compact simulator was designed to support the training from the regular full scope simulator which was already equipped in the Maanshan plant. The feature of this compact simulator focused on providing know-why training by the enhanced graphic display. The potential users were identified as senior operators, instructors and nuclear engineers. Total about 13 important systems were covered in the scope of the compact simulator, and multi-graphic displays from three color monitors mounted on the 10 feet compact panel were facilitated to help the user visualize detailed phenomena under scenarios of interest. (author)

HuPSON: the human physiology simulation ontology.

Science.gov (United States)

Gündel, Michaela; Younesi, Erfan; Malhotra, Ashutosh; Wang, Jiali; Li, Hui; Zhang, Bijun; de Bono, Bernard; Mevissen, Heinz-Theodor; Hofmann-Apitius, Martin

2013-11-22

Large biomedical simulation initiatives, such as the Virtual Physiological Human (VPH), are substantially dependent on controlled vocabularies to facilitate the exchange of information, of data and of models. Hindering these initiatives is a lack of a comprehensive ontology that covers the essential concepts of the simulation domain. We propose a first version of a newly constructed ontology, HuPSON, as a basis for shared semantics and interoperability of simulations, of models, of algorithms and of other resources in this domain. The ontology is based on the Basic Formal Ontology, and adheres to the MIREOT principles; the constructed ontology has been evaluated via structural features, competency questions and use case scenarios.The ontology is freely available at: http://www.scai.fraunhofer.de/en/business-research-areas/bioinformatics/downloads.html (owl files) and http://bishop.scai.fraunhofer.de/scaiview/ (browser). HuPSON provides a framework for a) annotating simulation experiments, b) retrieving relevant information that are required for modelling, c) enabling interoperability of algorithmic approaches used in biomedical simulation, d) comparing simulation results and e) linking knowledge-based approaches to simulation-based approaches. It is meant to foster a more rapid uptake of semantic technologies in the modelling and simulation domain, with particular focus on the VPH domain.

Lasertron performance simulation

International Nuclear Information System (INIS)

Dubrovin, A.; Coulon, J.P.

1987-05-01

This report presents a comparative simulation study of the Lasertron at different frequency and emission conditions, in view to establish choice criteria for future experiments. The RING program for these simulations is an improved version of the one presented in an other report. The self-consistent treatment of the R.F. extraction zone is added to it, together with the possibility to vary initial conditions to better describe the laser illumination and the electron extraction from cathode. Plane or curved cathodes are used [fr

Conservative Initial Mapping For Multidimensional Simulations of Stellar Explosions

International Nuclear Information System (INIS)

Chen, Ke-Jung; Heger, Alexander; Almgren, Ann

2012-01-01

Mapping one-dimensional stellar profiles onto multidimensional grids as initial conditions for hydrodynamics calculations can lead to numerical artifacts, one of the most severe of which is the violation of conservation laws for physical quantities such as energy and mass. Here we introduce a numerical scheme for mapping one-dimensional spherically-symmetric data onto multidimensional meshes so that these physical quantities are conserved. We validate our scheme by porting a realistic 1D Lagrangian stellar profile to the new multidimensional Eulerian hydro code CASTRO. Our results show that all important features in the profiles are reproduced on the new grid and that conservation laws are enforced at all resolutions after mapping.

The performance of the ATLAS initial detector layout for B-physics channels

International Nuclear Information System (INIS)

Epp, B.; Ghete, V.M.; Kuhn, D.; Zhang, Y.J.

2004-01-01

At the start-up of LHC one expects parts of the ATLAS detector to be missing. This layout is called initial layout, whereas the fully staged detector is called complete layout. B-physics channels were simulated, reconstructed and analyzed using the software tools of ATLAS data challenge-1 (DC1). The performance of the detector with respect to quantities relevant to the analysis of the B s → D s π channel and the validation of the full chain generation-simulation-reconstruction-analysis were evaluated for the initial and complete layout. (author)

Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

Science.gov (United States)

Diama, A.; Matthies, B.; Herwig, K. W.; Hansen, F. Y.; Criswell, L.; Mo, H.; Bai, M.; Taub, H.

2009-08-01

We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C24H50 denoted as C24) and dotriacontane (n-C32H66 denoted as C32) adsorbed on a graphite basal-plane surface. Our measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows of molecules in their all-trans conformation aligned with their long axis parallel to the surface and forming so-called lamellas of width approximately equal to the all-trans length of the molecule. The RC structure is uniaxially commensurate with the graphite surface in its [110] direction such that the distance between molecular rows in a lamella is 4.26 Å=√3 ag, where ag=2.46 Å is the lattice constant of the graphite basal plane. Molecules in adjacent rows of a lamella alternate in orientation between the carbon skeletal plane being parallel and perpendicular to the graphite surface. Upon heating, the crystalline monolayers transform to a "smectic" phase in which the inter-row spacing within a lamella expands by ˜10% and the molecules are predominantly oriented with the carbon skeletal plane parallel to the graphite surface. In the smectic phase, the MD simulations show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously.

Computer simulation of thermal plant operations

CERN Document Server

O'Kelly, Peter

2012-01-01

This book describes thermal plant simulation, that is, dynamic simulation of plants which produce, exchange and otherwise utilize heat as their working medium. Directed at chemical, mechanical and control engineers involved with operations, control and optimization and operator training, the book gives the mathematical formulation and use of simulation models of the equipment and systems typically found in these industries. The author has adopted a fundamental approach to the subject. The initial chapters provide an overview of simulation concepts and describe a suitable computer environment.

Simulation of reactivity-initiated accident transients on UO2-M5® fuel rods with ALCYONE V1.4 fuel performance code

Directory of Open Access Journals (Sweden)

Isabelle Guénot-Delahaie

2018-03-01

Full Text Available The ALCYONE multidimensional fuel performance code codeveloped by the CEA, EDF, and AREVA NP within the PLEIADES software environment models the behavior of fuel rods during irradiation in commercial pressurized water reactors (PWRs, power ramps in experimental reactors, or accidental conditions such as loss of coolant accidents or reactivity-initiated accidents (RIAs. As regards the latter case of transient in particular, ALCYONE is intended to predictively simulate the response of a fuel rod by taking account of mechanisms in a way that models the physics as closely as possible, encompassing all possible stages of the transient as well as various fuel/cladding material types and irradiation conditions of interest. On the way to complying with these objectives, ALCYONE development and validation shall include tests on PWR-UO2 fuel rods with advanced claddings such as M5® under “low pressure–low temperature” or “high pressure–high temperature” water coolant conditions.This article first presents ALCYONE V1.4 RIA-related features and modeling. It especially focuses on recent developments dedicated on the one hand to nonsteady water heat and mass transport and on the other hand to the modeling of grain boundary cracking-induced fission gas release and swelling. This article then compares some simulations of RIA transients performed on UO2-M5® fuel rods in flowing sodium or stagnant water coolant conditions to the relevant experimental results gained from tests performed in either the French CABRI or the Japanese NSRR nuclear transient reactor facilities. It shows in particular to what extent ALCYONE—starting from base irradiation conditions it itself computes—is currently able to handle both the first stage of the transient, namely the pellet-cladding mechanical interaction phase, and the second stage of the transient, should a boiling crisis occur.Areas of improvement are finally discussed with a view to simulating and

Effect of Initial Hydraulic Conditions on Capillary Rise in a Porous Medium: Pore-Network Modeling

KAUST Repository

Joekar-Niasar, V.

2012-01-01

The dynamics of capillary rise in a porous medium have been mostly studied in initially dry systems. As initial saturation and initial hydraulic conditions in many natural and industrial porous media can be variable, it is important to investigate the influence of initial conditions on the dynamics of the process. In this study, using dynamic pore-network modeling, we simulated capillary rise in a porous medium for different initial saturations (and consequently initial capillary pressures). Furthermore, the effect of hydraulic connectivity of the wetting phase in corners on the height and velocity of the wetting front was studied. Our simulation results show that there is a trade-off between capillary forces and trapping due to snap-off, which leads to a nonlinear dependence of wetting front velocity on initial saturation at the pore scale. This analysis may provide a possible answer to the experimental observations in the literature showing a non-monotonic dependency between initial saturation and the macroscopic front velocity. © Soil Science Society of America.

Role of the atmospheric mean state on the initiation of the Madden-Julian oscillation in a tropical channel model

Energy Technology Data Exchange (ETDEWEB)

Ray, Pallav; Zhang, Chidong [University of Miami, RSMAS/MPO, Miami, FL (United States); Moncrieff, Mitchell W.; Dudhia, Jim; Caron, Julie M.; Bruyere, Cindy [National Center for Atmospheric Research, Boulder, CO (United States); Ruby Leung, L. [Pacific Northwest National Laboratory, Richland, WA (United States)

2011-01-15

Tropical channel models, defined as models that are global in the zonal direction but bounded in the meridional direction, are particularly useful for simulating the Madden-Julian oscillation (MJO) and understanding its physical and dynamical basis. Influences from the extratropics through the lateral boundaries have been found to be essential to the reproduction of the initiation of certain MJO events. This led to a hypothesis that multi-year simulations using a tropical channel model would reproduce reasonable MJO statistics under the influence of prescribed lateral boundary conditions derived from global reanalyses. Interestingly, the MJO statistics in such a multi-year simulation by a high-resolution tropical channel model are not better than those from global climate models. The error in the atmospheric mean state is found to be a possible reason for the poor MJO statistics in the simulation. Nevertheless, even with a large error in the mean state, the multi-year simulation captures two MJO events previously found to be initiated by extratropical influences. However, the model does not reproduce a third event, whose initiation is not directly influenced by the extratropics. This implies that in the absence of dynamical interactions between the MJO and the lateral boundary conditions, the error in the mean state could be sufficient to prevent the MJO initiation. To explore this third MJO event further, a series of sensitivity tests are conducted. These tests show that the simulation of this event is neither critically influenced by the cumulus parameterization employed, nor the initial conditions when the model is integrated 2 weeks prior to the MJO initiation. The model captures this event when the MJO signal is already present in the initial conditions. The use of high-resolution sea surface temperature does not improve the simulation of the third MJO event. A higher-resolution nested domain covering the Indo-Pacific warm pool region and including a cloud

Initial-state parton shower kinematics for NLO event generators

International Nuclear Information System (INIS)

Odaka, Shigeru; Kurihara, Yoshimasa

2007-01-01

We are developing a consistent method to combine tree-level event generators for hadron collision interactions with those including one additional QCD radiation from the initial-state partons, based on the limited leading-log (LLL) subtraction method, aiming at an application to NLO event generators. In this method, a boundary between non-radiative and radiative processes necessarily appears at the factorization scale (μ F ). The radiation effects are simulated using a parton shower (PS) in non-radiative processes. It is therefore crucial in our method to apply a PS which well reproduces the radiation activities evaluated from the matrix-element (ME) calculations for radiative processes. The PS activity depends on the applied kinematics model. In this paper we introduce two models for our simple initial-state leading-log PS: a model similar to the 'old' PYTHIA-PS and a p T -prefixed model motivated by ME calculations. PS simulations employing these models are tested using W-boson production at LHC as an example. Both simulations show a smooth matching to the LLL subtracted W+1 jet simulation in the p T distribution of W bosons, and the summed p T spectra are stable against a variation of μ F , despite that the p T -prefixed PS results in an apparently harder p T spectrum. (orig.)

Euler-Lagrange Simulations of Shock Wave-Particle Cloud Interaction

Science.gov (United States)

Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Park, Chanyoung; Balachandar, S.

2017-11-01

Numerical experiments of shock interacting with an evolving and fixed cloud of particles are performed. In these simulations we use Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. As validation, we use Sandia Multiphase Shock Tube experiments and particle-resolved simulations. The particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In the simulations evolving the particle cloud, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. Measurements of particle dispersion are made at different initial volume fractions. A detailed analysis of the influence of initial conditions on the evolution of the particle cloudis presented. The early time behavior of the models is studied in the fixed bed simulations at varying volume fractions and shock Mach numbers.The mean gas quantities are measured in the context of 1-way and 2-way coupled simulations. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.

Moving State Marine SINS Initial Alignment Based on High Degree CKF

Directory of Open Access Journals (Sweden)

Yong-Gang Zhang

2014-01-01

Full Text Available A new moving state marine initial alignment method of strap-down inertial navigation system (SINS is proposed based on high-degree cubature Kalman filter (CKF, which can capture higher order Taylor expansion terms of nonlinear alignment model than the existing third-degree CKF, unscented Kalman filter and central difference Kalman filter, and improve the accuracy of initial alignment under large heading misalignment angle condition. Simulation results show the efficiency and advantage of the proposed initial alignment method as compared with existing initial alignment methods for the moving state SINS initial alignment with large heading misalignment angle.

Simulation of the collapse and dissipation of Langmuir wave packets

International Nuclear Information System (INIS)

Newman, D.L.; Winglee, R.M.; Robinson, P.A.; Glanz, J.; Goldman, M.V.

1990-01-01

The collapse of isolated Langmuir wave packets is studied numerically in two dimensions using both particle-in-cell (PIC) simulations and by integrating the Zakharov partial differential equations (PDE's). The initial state consists of a localized Langmuir wave packet in an ion background that either is uniform or has a profile representative of the density wells in which wave packets form during strong plasma turbulence. Collapse thresholds are determined numerically and compared to analytical estimates. A model in which Langmuir damping is significantly stronger than Landau damping is constructed which, when included in the PDE simulations, yields good agreement with the collapse dynamics observed in PIC simulations for wave packets with initial wave energy densities small compared to the thermal level. For more intense initial Langmuir fields, collapse is arrested in PIC simulations at lower field strengths than in PDE simulations. Neither nonlinear saturation of the density perturbation nor fluid electron nonlinearities can account for the difference between simulation methods in this regime. However, at these wave levels inhomogeneous electron heating and coherent jets of transit-time accelerated electrons in phase space are observed, resulting in further enhancement of wave damping and the consequent reduction of fields in the PIC simulations

Simulating video-assisted thoracoscopic lobectomy: a virtual reality cognitive task simulation.

Science.gov (United States)

Solomon, Brian; Bizekis, Costas; Dellis, Sophia L; Donington, Jessica S; Oliker, Aaron; Balsam, Leora B; Zervos, Michael; Galloway, Aubrey C; Pass, Harvey; Grossi, Eugene A

2011-01-01

Current video-assisted thoracoscopic surgery training models rely on animals or mannequins to teach procedural skills. These approaches lack inherent teaching/testing capability and are limited by cost, anatomic variations, and single use. In response, we hypothesized that video-assisted thoracoscopic surgery right upper lobe resection could be simulated in a virtual reality environment with commercial software. An anatomy explorer (Maya [Autodesk Inc, San Rafael, Calif] models of the chest and hilar structures) and simulation engine were adapted. Design goals included freedom of port placement, incorporation of well-known anatomic variants, teaching and testing modes, haptic feedback for the dissection, ability to perform the anatomic divisions, and a portable platform. Preexisting commercial models did not provide sufficient surgical detail, and extensive modeling modifications were required. Video-assisted thoracoscopic surgery right upper lobe resection simulation is initiated with a random vein and artery variation. The trainee proceeds in a teaching or testing mode. A knowledge database currently includes 13 anatomic identifications and 20 high-yield lung cancer learning points. The "patient" is presented in the left lateral decubitus position. After initial camera port placement, the endoscopic view is displayed and the thoracoscope is manipulated via the haptic device. The thoracoscope port can be relocated; additional ports are placed using an external "operating room" view. Unrestricted endoscopic exploration of the thorax is allowed. An endo-dissector tool allows for hilar dissection, and a virtual stapling device divides structures. The trainee's performance is reported. A virtual reality cognitive task simulation can overcome the deficiencies of existing training models. Performance scoring is being validated as we assess this simulator for cognitive and technical surgical education. Copyright © 2011. Published by Mosby, Inc.

Molecular dynamics simulations indicate that deoxyhemoglobin, oxyhemoglobin, carboxyhemoglobin, and glycated hemoglobin under compression and shear exhibit an anisotropic mechanical behavior.

Science.gov (United States)

Yesudasan, Sumith; Wang, Xianqiao; Averett, Rodney D

2018-05-01

We developed a new mechanical model for determining the compression and shear mechanical behavior of four different hemoglobin structures. Previous studies on hemoglobin structures have focused primarily on overall mechanical behavior; however, this study investigates the mechanical behavior of hemoglobin, a major constituent of red blood cells, using steered molecular dynamics (SMD) simulations to obtain anisotropic mechanical behavior under compression and shear loading conditions. Four different configurations of hemoglobin molecules were considered: deoxyhemoglobin (deoxyHb), oxyhemoglobin (HbO 2 ), carboxyhemoglobin (HbCO), and glycated hemoglobin (HbA 1C ). The SMD simulations were performed on the hemoglobin variants to estimate their unidirectional stiffness and shear stiffness. Although hemoglobin is structurally denoted as a globular protein due to its spherical shape and secondary structure, our simulation results show a significant variation in the mechanical strength in different directions (anisotropy) and also a strength variation among the four different hemoglobin configurations studied. The glycated hemoglobin molecule possesses an overall higher compressive mechanical stiffness and shear stiffness when compared to deoxyhemoglobin, oxyhemoglobin, and carboxyhemoglobin molecules. Further results from the models indicate that the hemoglobin structures studied possess a soft outer shell and a stiff core based on stiffness.

Stochastic modeling of pitting corrosion: A new model for initiation and growth of multiple corrosion pits

International Nuclear Information System (INIS)

Valor, A.; Caleyo, F.; Alfonso, L.; Rivas, D.; Hallen, J.M.

2007-01-01

In this work, a new stochastic model capable of simulating pitting corrosion is developed and validated. Pitting corrosion is modeled as the combination of two stochastic processes: pit initiation and pit growth. Pit generation is modeled as a nonhomogeneous Poisson process, in which induction time for pit initiation is simulated as the realization of a Weibull process. In this way, the exponential and Weibull distributions can be considered as the possible distributions for pit initiation time. Pit growth is simulated using a nonhomogeneous Markov process. Extreme value statistics is used to find the distribution of maximum pit depths resulting from the combination of the initiation and growth processes for multiple pits. The proposed model is validated using several published experiments on pitting corrosion. It is capable of reproducing the experimental observations with higher quality than the stochastic models available in the literature for pitting corrosion

Stochastic modeling of pitting corrosion: A new model for initiation and growth of multiple corrosion pits

Energy Technology Data Exchange (ETDEWEB)

Valor, A. [Facultad de Fisica, Universidad de La Habana, San Lazaro y L, Vedado, 10400 Havana (Cuba); Caleyo, F. [Departamento de Ingenieria, Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico)]. E-mail: fcaleyo@gmail.com; Alfonso, L. [Departamento de Ingenieria, Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico); Rivas, D. [Departamento de Ingenieria, Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico); Hallen, J.M. [Departamento de Ingenieria, Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico)

2007-02-15

In this work, a new stochastic model capable of simulating pitting corrosion is developed and validated. Pitting corrosion is modeled as the combination of two stochastic processes: pit initiation and pit growth. Pit generation is modeled as a nonhomogeneous Poisson process, in which induction time for pit initiation is simulated as the realization of a Weibull process. In this way, the exponential and Weibull distributions can be considered as the possible distributions for pit initiation time. Pit growth is simulated using a nonhomogeneous Markov process. Extreme value statistics is used to find the distribution of maximum pit depths resulting from the combination of the initiation and growth processes for multiple pits. The proposed model is validated using several published experiments on pitting corrosion. It is capable of reproducing the experimental observations with higher quality than the stochastic models available in the literature for pitting corrosion.

NU-IN: Nucleotide evolution and input module for the EvolSimulator genome simulation platform

Directory of Open Access Journals (Sweden)

Barker Michael S

2010-08-01

Full Text Available Abstract Background There is increasing demand to test hypotheses that contrast the evolution of genes and gene families among genomes, using simulations that work across these levels of organization. The EvolSimulator program was developed recently to provide a highly flexible platform for forward simulations of amino acid evolution in multiple related lineages of haploid genomes, permitting copy number variation and lateral gene transfer. Synonymous nucleotide evolution is not currently supported, however, and would be highly advantageous for comparisons to full genome, transcriptome, and single nucleotide polymorphism (SNP datasets. In addition, EvolSimulator creates new genomes for each simulation, and does not allow the input of user-specified sequences and gene family information, limiting the incorporation of further biological realism and/or user manipulations of the data. Findings We present modified C++ source code for the EvolSimulator platform, which we provide as the extension module NU-IN. With NU-IN, synonymous and non-synonymous nucleotide evolution is fully implemented, and the user has the ability to use real or previously-simulated sequence data to initiate a simulation of one or more lineages. Gene family membership can be optionally specified, as well as gene retention probabilities that model biased gene retention. We provide PERL scripts to assist the user in deriving this information from previous simulations. We demonstrate the features of NU-IN by simulating genome duplication (polyploidy in the presence of ongoing copy number variation in an evolving lineage. This example is initiated with real genomic data, and produces output that we analyse directly with existing bioinformatic pipelines. Conclusions The NU-IN extension module is a publicly available open source software (GNU GPLv3 license extension to EvolSimulator. With the NU-IN module, users are now able to simulate both drift and selection at the nucleotide

Initiation Processes of the Tropical Intraseasonal Variability Simulated in an Aqua-Planet Experiment: What is the Intrinsic Mechanism for MJO Onset?

Science.gov (United States)

Takasuka, Daisuke; Satoh, Masaki; Miyakawa, Tomoki; Miura, Hiroaki

2018-04-01

To understand the intrinsic onset mechanism of the Madden-Julian Oscillation (MJO), we simulated a set of initiation processes of MJO-like disturbances in 10 year aqua-planet experiments using a global atmospheric model with a 56 km horizontal mesh and an explicit cloud scheme. Under a condition with a zonally nonuniform sea surface temperature (SST) in the tropics, we reproduced MJO-like disturbances over the western warm pool region. The lagged-composite analysis of detected MJO-like disturbances clarifies the time sequence of three-dimensional dynamic and moisture fields prior to the onset. We found that midtropospheric moistening, a condition that is favorable for deep convection, is particularly obvious in the initiation region 5-9 days before onset. The moistening is caused by two-dimensional horizontal advection due to cross-equatorial shallow circulations associated with mixed Rossby-gravity waves, as well as anomalous poleward flows of a negative Rossby response to suppressed convection. When the midtroposphere is sufficiently moistened, lower tropospheric signals of circumnavigating Kelvin waves trigger active convection. The surface latent heat flux (LHF) feedback contributes to the initial stages of convective organization, while the cloud-radiation feedback contributes to later stages. Sensitivity experiments suggest that circumnavigating Kelvin waves regulate the period of MJO-like disturbances because of efficient convective triggering and that the LHF feedback contributes to rapid convective organization. However, the experiments also reveal that both conditions are not necessary for the existence of MJO-like disturbances. Implications for the relevance of these mechanisms for MJO onset are also discussed.

Empowering stakeholders through simulation in water resources planning

International Nuclear Information System (INIS)

Palmer, R.N.; Keyes, A.M.; Fisher, S.

1993-01-01

During the past two years, researchers at the University of Washington (UW) have had the unique opportunity to facilitate and observe the development of drought planning activities associated with the National Drought Study (NDS) and its Drought Preparedness Studies (DPS) sites as sponsored by the Institute of Water Resources of the US Army Corps of Engineers. Each of the DPS sites is unique, with different study objectives and institutional constraints. However, one uniform requirement of the study is to develop tactical and strategic drought plans that can be successfully implemented within the study region. At the onset of the study, it was recognized that successful implementation is directly related to the active involvement of affected parties and agencies (denoted as stakeholders) and the degree to which they support the plan's conclusions. Their involvement is also necessary because the problems addressed by the DPS's require the experience and knowledge of a variety of water resource interests in order to arrive at effective alternatives. Their support of the plan conclusions enables regional implementation. Several techniques were used to encourage stakeholder participation in the planning process. Individuals representing the stakeholders had a wide range of professional backgrounds. This paper concentrates on one specific approach found useful in encouraging comprehensive and meaningful participation by a wide range of stakeholders; the development of object-oriented simulation models for the water resource systems under study. Simulation models were to develop tactical and strategic drought plans and to ensure the acceptance of the plans by building consensus among the stakeholders. The remainder of this paper describes: how simulation models became a part of the National Drought Study, procedures used to develop the DPS models, and how the model empowered stakeholders

NPP Krsko simulator training for operations personnel

International Nuclear Information System (INIS)

Pribozic, F.; Krajnc, J.

2000-01-01

Acquisition of a full scope replica simulator represents an important achievement for Nuclear power Plant Krsko. Operating nuclear power plant systems is definitely a set of demanding and complex tasks. The most important element in the goal of assuring capabilities for handling such tasks is efficient training of operations personnel who manipulate controls in the main control room. Use of a simulator during the training process is essential and can not be substituted by other techniques. This article gives an overview of NPP Krsko licensed personnel training historical background, current experience and plans for future training activities. Reactor operator initial training lasts approximately two and a half years. Training is divided into several phases, consisting of theoretical and practical segments, including simulator training. In the past, simulator initial training and annual simulator retraining was contracted, thus operators were trained on non-specific full scope simulators. Use of our own plant specific simulator and associated infrastructure will have a significant effect on the operations personnel training process and, in addition, will also support secondary uses, with the common goal to improve safe and reliable plant operation. A regular annual retraining program has successfully started. Use of the plant specific simulator assures consistent training and good management oversight, enhances conformity of operational practices and supports optimization of operating procedures. (author)

The Sustainable Leadership Simulator (SLS)

DEFF Research Database (Denmark)

Kjærgaard, Thomas; Edgeman, Rick; Grewatsch, Sylvia

Some businesses and some industries are demonstrating leadership on sustainability issues through cross-organizational collaboration and innovation, but the diffusion and scaling up of the sustainability solutions often termed Best Practices has been identified as a key challenge for future...... sustainable development by the UN (Leisinger and Bakker, 2013). Over a little more than a decade global initiatives like the Global Reporting Initiative (GRI) and the UN Global Compact (UNGC) has demonstrated leadership by addressing these issues through voluntary commitment from thousands of corporations...... by the systematic application of more innovative governance mechanisms. This article currently conceptualizes the UN PRME-endorsed (Haertle, 2013) Sustainability Leadership Simulator (SLS), which at a minimum level of operationalization will be an open source based and hence impactful online training simulator...

A study on the thermal expansion characteristics of simulated spent fuel and simulated DUPIC fuel

International Nuclear Information System (INIS)

Kang, Kweon Ho; Ryu, H. J.; Kim, H. S.; Song, K. C.; Yang, M. S.

2001-10-01

Thermal expansions of simulated spent PWR fuel and simulated DUPIC fuel were studied using a dilatometer in the temperature range from 298 to 1900 K. The densities of simulated spent PWR fuel and simulated DUPIC fuel used in the measurement were 10.28 g/cm3 (95.35 % of TD) and 10.26 g/cm3 (95.14 % of TD), respectively. Their linear thermal expansions of simulated fuels are higher than that of UO2, and the difference between these fuels and UO2 increases progressively as temperature increases. However, the difference between simulated spent PWR fuel and simulated DUPIC fuel can hardly be observed. For the temperature range from 298 to 1900 K, the values of the average linear thermal expansion coefficients for simulated spent PWR fuel and simulated DUPIC fuel are 1.391 10-5 and 1.393 10-5 K-1, respectively. As temperature increases to 1900 K, the relative densities of simulated spent PWR fuel and simulated DUPIC fuel decrease to 93.81 and 93.76 % of initial densities at 298 K, respectively

Initiation of Gaseous Detonation by Conical Projectiles

Science.gov (United States)

Verreault, Jimmy

qualitatively well with the experimental results for relatively blunt projectiles (cone half-angle larger than 35°) and low mixture pressures (lower than 100 kPa). The trend of the critical Damköhler number calculated along the projectile cone surface was similar to that of the experimental results for slender cones (cone half-angles lower 35°) and high mixture pressures (higher than 100 kPa). Steady 2D simulations of reacting flows over finite wedges using the method of characteristics with a one-step Arrhenius chemical reaction model reproduced the three regimes observed for direct initiation of a detonation: the subcritical, critical and supercritical regimes. It is shown that in order for a 2D wedge to be equivalent to the problem of blast initiation of a detonation (which is the essence of the Lee-Vasiljev model), the Mach number normal to the oblique shock needs to be greater than 50 and the wedge angle has to be smaller than 30°. Simulations of reacting flows over semi-infinite wedges and cones were validated with CFD results. Excellent agreement was reached between the angle of overdriven oblique detonations obtained from the simulations and those from a polar analysis. For wedge or cone angles equal or lower than the minimum angle for which an oblique detonation is attached (according to the polar analysis), a Chapman-Jouguet oblique detonation was initiated. In the conical configuration, the curvature around the cone axis allowed an oblique detonation to be self-sustained at an angle less than without the curvature effect. At larger activation energies, the initiation process of an oblique detonation wave at the tip of a semi-infinite wedge or cone was identified. Unsteady 2D computational simulations were also conducted and showed the cellular structure of an oblique detonation wave. Instabilities in the form of transverse shock waves along the oblique detonation front arise for large activation energies.

US Air Force 1989 Research Initiation Program. Volume 2.

Science.gov (United States)

1992-06-25

Since acpwc is constant with height, (26) can be rewritten as + a ! t - Ecrit ) - - • (27) In the above, following Hack etai. (1984), we are using a to...zt Mp(zm) - Jacpa(q - Ecrit )dz, Zm where Mp(zm) denotes the vertical large-scale flux of precipitation falling through the level z - zm; and the...of the basic problems associated with monitoring a comprehensive nuclear test ban treaty is that of discriminating between small explosions and

Fast core prediction simulator for load follow control

International Nuclear Information System (INIS)

Yim, Man Sung; Lee, Sang Hoon; Lee, Un Chul

1990-01-01

An operator-assisting system for the reactor core control under power changing operating condition was developed. The system is consisted of core simulator routine and Xenon and Iodine initial condition generation routine. The initial condition generation routine, without exactly knowing the core status, is capable of providing accurate number densities and axial offset conditions of Xenon and Iodine after several hours of predictor- corrector calculations using the plant instrumentation signals of power level and power axial offset. The core simulator routine, even with the two node core model, gives equivalently accurate results as the one-dimensional model for the core behaviour simulation under power changing condition and can provide proper control strategies for load follow operation. The core simulator can also be used by the operator to develop remedial actions to restore the distorted power distribution by using its prediction capability

Disruption simulation for the EAST plasma

International Nuclear Information System (INIS)

Niu Xingping; Wu Bin

2007-01-01

The disruptions due to vertical displacement event for the EAST plasma are simulated in this article by using the TSC program. Meanwhile, the evolutions of the halo current and stress on vacuum vessel are calculated; the disruptions at different initial conditions are compared with each other, and killer pellet injection is simulated for the device fast shutting-down. (authors)

Development of a full scope reactor engineering simulator

International Nuclear Information System (INIS)

Venhuizen, J.R.; Laats, E.T.

1988-01-01

An engineering laboratory is pursuing the development of an engineering simulator for use by several agencies of the U.S. Government. According to the authors, this simulator will provide the highest fidelity simulation with initial objectives for studying augmented nuclear reactor operator training, and later for advanced concepts testing as applicable to control room accident diagnosis and management

On crack initiation in notched, cross-plied polymer matrix composites

Science.gov (United States)

Yang, Q. D.; Schesser, D.; Niess, M.; Wright, P.; Mavrogordato, M. N.; Sinclair, I.; Spearing, S. M.; Cox, B. N.

2015-05-01

The physics of crack initiation in a polymer matrix composite are investigated by varying the modeling choices made in simulations and comparing the resulting predictions with high-resolution in situ images of cracks. Experimental data were acquired using synchrotron-radiation computed tomography (SRCT) at a resolution on the order of 1 μm, which provides detailed measurement of the location, shape, and size of small cracks, as well as the crack opening and shear displacements. These data prove sufficient to discriminate among competing physical descriptions of crack initiation. Simulations are executed with a high-fidelity formulation, the augmented finite element method (A-FEM), which permits consideration of coupled damage mechanisms, including both discrete cracks and fine-scale continuum damage. The discrete cracks are assumed to be nonlinear fracture events, governed by reasonably general mixed-mode cohesive laws. Crack initiation is described in terms of strength parameters within the cohesive laws, so that the cohesive law provides a unified model for crack initiation and growth. Whereas the cracks investigated are typically 1 mm or less in length, the fine-scale continuum damage refers to irreversible matrix deformation occurring over gauge lengths extending down to the fiber diameter (0.007 mm). We find that the location and far-field stress for crack initiation are predicted accurately only if the variations of local stress within plies and in the presence of stress concentrators (notches, etc.) are explicitly computed and used in initiation criteria; stress redistribution due to matrix nonlinearity that occurs prior to crack initiation is accounted for; and a mixed-mode criterion is used for crack initiation. If these factors are not all considered, which is the case for commonly used failure criteria, predictions of the location and far-field stress for initiation are not accurate.

Assessing the Uncertainty of Tropical Cyclone Simulations in NCAR's Community Atmosphere Model

Directory of Open Access Journals (Sweden)

Kevin A Reed

2011-08-01

Full Text Available The paper explores the impact of the initial-data, parameter and structural model uncertainty on the simulation of a tropical cyclone-like vortex in the National Center for Atmospheric Research's (NCAR Community Atmosphere Model (CAM. An analytic technique is used to initialize the model with an idealized weak vortex that develops into a tropical cyclone over ten simulation days. A total of 78 ensemble simulations are performed at horizontal grid spacings of 1.0°, 0.5° and 0.25° using two recently released versions of the model, CAM 4 and CAM 5. The ensemble members represent simulations with random small-amplitude perturbations of the initial conditions, small shifts in the longitudinal position of the initial vortex and runs with slightly altered model parameters. The main distinction between CAM 4 and CAM 5 lies within the physical parameterization suite, and the simulations with both CAM versions at the varying resolutions assess the structural model uncertainty. At all resolutions storms are produced with many tropical cyclone-like characteristics. The CAM 5 simulations exhibit more intense storms than CAM 4 by day 10 at the 0.5° and 0.25° grid spacings, while the CAM 4 storm at 1.0° is stronger. There are also distinct differences in the shapes and vertical profiles of the storms in the two variants of CAM. The ensemble members show no distinction between the initial-data and parameter uncertainty simulations. At day 10 they produce ensemble root-mean-square deviations from an unperturbed control simulation on the order of 1--5 m s^-1 for the maximum low-level wind speed and 2--10 hPa for the minimum surface pressure. However, there are large differences between the two CAM versions at identical horizontal resolutions. It suggests that the structural uncertainty is more dominant than the initial-data and parameter uncertainties in this study. The uncertainty among the ensemble members is assessed and quantified.

Real-time numerical shake prediction and updating for earthquake early warning

Science.gov (United States)

Wang, Tianyun; Jin, Xing; Wei, Yongxiang; Huang, Yandan

2017-12-01

Ground motion prediction is important for earthquake early warning systems, because the region's peak ground motion indicates the potential disaster. In order to predict the peak ground motion quickly and precisely with limited station wave records, we propose a real-time numerical shake prediction and updating method. Our method first predicts the ground motion based on the ground motion prediction equation after P waves detection of several stations, denoted as the initial prediction. In order to correct the prediction error of the initial prediction, an updating scheme based on real-time simulation of wave propagation is designed. Data assimilation technique is incorporated to predict the distribution of seismic wave energy precisely. Radiative transfer theory and Monte Carlo simulation are used for modeling wave propagation in 2-D space, and the peak ground motion is calculated as quickly as possible. Our method has potential to predict shakemap, making the potential disaster be predicted before the real disaster happens. 2008 M S8.0 Wenchuan earthquake is studied as an example to show the validity of the proposed method.

NASA/FAA helicopter simulator workshop

Science.gov (United States)

Larsen, William E. (Editor); Randle, Robert J., Jr. (Editor); Bray, Richard S. (Editor); Zuk, John (Editor)

1992-01-01

A workshop was convened by the FAA and NASA for the purpose of providing a forum at which leading designers, manufacturers, and users of helicopter simulators could initiate and participate in a development process that would facilitate the formulation of qualification standards by the regulatory agency. Formal papers were presented, special topics were discussed in breakout sessions, and a draft FAA advisory circular defining specifications for helicopter simulators was presented and discussed. A working group of volunteers was formed to work with the National Simulator Program Office to develop a final version of the circular. The workshop attracted 90 individuals from a constituency of simulator manufacturers, training organizations, the military, civil regulators, research scientists, and five foreign countries.

Effect of a Home-Based Lifestyle Intervention on Breastfeeding Initiation Among Socioeconomically Disadvantaged African American Women with Overweight or Obesity.

Science.gov (United States)

Lewkowitz, Adam K; López, Julia D; Stein, Richard I; Rhoades, Janine S; Schulz, Rosa C; Woolfolk, Candice L; Macones, George A; Haire-Joshu, Debra; Cahill, Alison G

2018-06-18

Socioeconomically disadvantaged (SED) African American women with overweight or obesity are less likely to breastfeed. To test whether a home-based lifestyle intervention impacts breastfeeding initiation rates in SED African American women with overweight or obesity. This was a secondary analysis of a randomized controlled trial from October 2012 to March 2016 at a university-based hospital within the LIFE-Moms consortium. SED African American women with overweight or obesity and singleton gestations were randomized by 16 weeks to Parents as Teachers (PAT)-a home-based parenting support and child development educational intervention-or PAT+, PAT with additional content on breastfeeding. Participants completed a breastfeeding survey. Outcomes included breastfeeding initiation and reasons for not initiating or not continuing breastfeeding. One hundred eighteen women were included: 59 in PAT+; 59 in PAT. Breastfeeding initiation rates were similar in each group (78.00% in PAT+; 74.58% in PAT). On a one to four scale, with four denoting "very important," women in PAT+ and PAT were equally likely to rate their beliefs that formula was better than breast milk or breastfeeding would be too inconvenient as the most important reasons to not initiate breastfeeding. On the same scale, women similarly rated their difficulty latching or concern for low milk supply as the most important reasons for breastfeeding cessation. SED African American women with overweight or obesity who received a home-based educational intervention had higher breastfeeding rates than is reported nationally for black women (59%). However, the intervention with more breastfeeding content did not further increase breastfeeding rates or impact reasons for breastfeeding cessation. ClinicalTrials.gov : NCT01768793.

Optimization approach of background value and initial item for improving prediction precision of GM(1,1) model

Institute of Scientific and Technical Information of China (English)

Yuhong Wang; Qin Liu; Jianrong Tang; Wenbin Cao; Xiaozhong Li

2014-01-01

A combination method of optimization of the back-ground value and optimization of the initial item is proposed. The sequences of the unbiased exponential distribution are simulated and predicted through the optimization of the background value in grey differential equations. The principle of the new information priority in the grey system theory and the rationality of the initial item in the original GM(1,1) model are ful y expressed through the improvement of the initial item in the proposed time response function. A numerical example is employed to il ustrate that the proposed method is able to simulate and predict sequences of raw data with the unbiased exponential distribution and has better simulation performance and prediction precision than the original GM(1,1) model relatively.

A harmonic transition state theory model for defect initiation in crystals

International Nuclear Information System (INIS)

Delph, T J; Cao, P; Park, H S; Zimmerman, J A

2013-01-01

We outline here a model for the initiation of defects in crystals based upon harmonic transition state theory (hTST). This model combines a previously developed model for zero-temperature defect initiation with a multi-dimensional hTST model that is capable of accurately predicting the effects of temperature and loading rate upon defect initiation. The model has several features that set it apart from previous efforts along these lines, most notably a straightforward method of determining the energy barrier between adjacent equilibrium states that does not depend upon a priori information concerning the nature of the defect. We apply the model to two examples, triaxial stretching of a perfect fcc crystal and nanoindentation of a gold substrate. Very good agreement is found between the predictions of the model and independent molecular dynamics (MD) simulations. Among other things, the model predicts a strong dependence of the defect initiation behavior upon the loading parameter. A very attractive feature of this model is that it is valid for arbitrarily slow loading rates, in particular loading rates achievable in the laboratory, and suffers from none of the limitations in this regard inherent in MD simulations. (paper)

Reconstruction of initial pressure from limited view photoacoustic images using deep learning

Science.gov (United States)

Waibel, Dominik; Gröhl, Janek; Isensee, Fabian; Kirchner, Thomas; Maier-Hein, Klaus; Maier-Hein, Lena

2018-02-01

Quantification of tissue properties with photoacoustic (PA) imaging typically requires a highly accurate representation of the initial pressure distribution in tissue. Almost all PA scanners reconstruct the PA image only from a partial scan of the emitted sound waves. Especially handheld devices, which have become increasingly popular due to their versatility and ease of use, only provide limited view data because of their geometry. Owing to such limitations in hardware as well as to the acoustic attenuation in tissue, state-of-the-art reconstruction methods deliver only approximations of the initial pressure distribution. To overcome the limited view problem, we present a machine learning-based approach to the reconstruction of initial pressure from limited view PA data. Our method involves a fully convolutional deep neural network based on a U-Net-like architecture with pixel-wise regression loss on the acquired PA images. It is trained and validated on in silico data generated with Monte Carlo simulations. In an initial study we found an increase in accuracy over the state-of-the-art when reconstructing simulated linear-array scans of blood vessels.

Simulation of burning plasma dynamics in ITER

International Nuclear Information System (INIS)

Wang, J.F.; Amano, T.; Ogawa, Y.; Inoue, N.

1996-02-01

Dynamics of burning plasma for various transient situations in ITER plasma has been simulated with a 1.5-dimensional up-down asymmetry Tokamak Transport Simulation Code (TTSC). We have mainly paid attention to intrinsic plasma transport processes such as the confinement improvement and the change of plasma profiles. It is shown that a large excursion of the fusion power takes place with a small improvement of the plasma confinement; e.g., an increase of the global energy confinement by a factor of 1.22 yields the fusion power excursion of ∼ 30% within a few seconds. Any feedback control of fueling D-T gas is difficult to respond to this short time scale of fusion power transient. The effect of the plasma profile on the fusion power excursion has been studied, by changing the particle transport denoted by the inward pinch parameter C V . It is found that the fusion power excursion is mild and slow, and the feedback control is quite effective in suppressing the fusion power excursion and in shortening the duration time of power transient in this case. The change in the pumping efficiency has also been studied and a large excursion of the fusion power has not been observed, because of the decrease in the fuel density itself in the case of the increase in the pumping efficiency, and the helium ash accumulation in the case of the decrease in the pumping efficiency. Finally it is shown that the MHD sawteeth activity leads to the fusion power fluctuation of ± 20%, although it is helpful for the helium ash exhaust. (author)

Initial kinetics of the direct sulfation of limestone

DEFF Research Database (Denmark)

Hu, Guilin; Shang, Lei; Dam-Johansen, Kim

2008-01-01

The initial kinetics of direct sulfation of Faxe Bryozo, a porous bryozoan limestone was studied in the temperature interval from 873 to 973 K in a pilot entrained flow reactor with very short reaction times (between 0.1 and 0.6 s). The initial conversion rate of the limestone - for conversions...... less than 0.3% - was observed to be significantly promoted by higher SO2 concentrations and lower CO2 concentrations, whereas 02 showed negligible influence. A mathematical model for the sulfation of limestone involving chemical reaction at calcite grain surfaces and solid-state diffusion of carbonate...... ions in calcite grains is established. The validity of the model is limited to the initial sulfation period, in which nucleation of the solid product calcium sulphate is not started. This theoretical reaction-diffusion model gives a good simulation of the initial kinetics of the direct sulfation...

A Monte-Carlo Simulation of Light Propagation in Sea Water

National Research Council Canada - National Science Library

Brennan, Mike

1997-01-01

.... Assumptions made in the implementation of the program are discussed. Results of some initial simulations are presented, together with data obtained during a recent LADS sortie for comparison with the simulations...

Simulation of crack propagation in steel plate with strain softening model

Energy Technology Data Exchange (ETDEWEB)

Chan, O.B.; Elwi, A.E.; Grondin, G.Y.

2006-05-15

A new material model for simulating the fracture behaviour of structural steel was presented. Recent research on crack initiation and continuum damage mechanics was presented. A modified continuum damage model was also evaluated. Strain softening elements were then used to simulate material cracks in a steel structure. The analysis then compared load versus displacement and load versus clip-gauge displacement curves from various different experimental and numerical studies. A finite element analysis technique was used to simulate the fracture behaviour of 3-points bending specimens. Results of the analysis showed that the model predicted 90 per cent of the load and stress intensity factor at fracture initiation. A BE 365 electric shovel boom was used in the study to simulate fracture behaviour. Coupon test specimens were used to validate analysis predictions. It was concluded that the model was able to reduce the stiffness of the boom when the softening element reached yield strength limits during fracture initiation. 29 refs., 12 tabs., 58 figs.

Color Gradients Within Globular Clusters: Restricted Numerical Simulation

Directory of Open Access Journals (Sweden)

Young-Jong Sohn

1997-06-01

Full Text Available The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salpeter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpeter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.

Ravenscar Computational Model compliant AADL Simulation on LEON2

Directory of Open Access Journals (Sweden)

Roberto Varona-Gómez

2013-02-01

Full Text Available AADL has been proposed for designing and analyzing SW and HW architectures for real-time mission-critical embedded systems. Although the Behavioral Annex improves its simulation semantics, AADL is a language for analyzing architectures and not for simulating them. AADS-T is an AADL simulation tool that supports the performance analysis of the AADL specification throughout the refinement process from the initial system architecture until the complete, detailed application and execution platform are developed. In this way, AADS-T enables the verification of the initial timing constraints during the complete design process. In this paper we focus on the compatibility of AADS-T with the Ravenscar Computational Model (RCM as part of the TASTE toolset. Its flexibility enables AADS-T to support different processors. In this work we have focused on performing the simulation on a LEON2 processor.

Simulations of roughness initiation and growth on railway rails

Science.gov (United States)

Sheng, X.; Thompson, D. J.; Jones, C. J. C.; Xie, G.; Iwnicki, S. D.; Allen, P.; Hsu, S. S.

2006-06-01

A model for the prediction of the initiation and growth of roughness on the rail is presented. The vertical interaction between a train and the track is calculated as a time history for single or multiple wheels moving on periodically supported rails, using a wavenumber-based approach. This vertical dynamic wheel/rail force arises from the varying stiffness due to discrete supports (i.e. parametric excitation) and the roughness excitation on the railhead. The tangential contact problem between the wheel and rail is modelled using an unsteady two-dimensional approach and also using the three-dimensional contact model, FASTSIM. This enables the slip and stick regions in the contact patch to be identified from the input geometry and creepage between the wheel and rail. The long-term wear growth is then predicted by applying repeated passages of the vehicle wheelsets, as part of an iterative solution.

The Simulation Intranet Architecture

Energy Technology Data Exchange (ETDEWEB)

Holmes, V.P.; Linebarger, J.M.; Miller, D.J.; Vandewart, R.L.

1998-12-02

The Simdarion Infranet (S1) is a term which is being used to dcscribc one element of a multidisciplinary distributed and distance computing initiative known as DisCom2 at Sandia National Laboratory (http ct al. 1998). The Simulation Intranet is an architecture for satisfying Sandia's long term goal of providing an end- to-end set of scrviccs for high fidelity full physics simu- lations in a high performance, distributed, and distance computing environment. The Intranet Architecture group was formed to apply current distributed object technologies to this problcm. For the hardware architec- tures and software models involved with the current simulation process, a CORBA-based architecture is best suited to meet Sandia's needs. This paper presents the initial desi-a and implementation of this Intranct based on a three-tier Network Computing Architecture(NCA). The major parts of the architecture include: the Web Cli- ent, the Business Objects, and Data Persistence.

Initial ACTR retrieval technology evaluation test material recommendations

International Nuclear Information System (INIS)

Powell, M.R.

1996-04-01

Millions of gallons of radiaoctive waste are contained in underground storage tanks at Hanford (SE Washington). Techniques for retrieving much of this waste from the storage tanks have been developed. Current baseline approach is to use sluice jets for single-shell tanks and mixer pumps for double-shell tanks. The Acquire Commercial Technology for Retrieval (ACTR) effort was initiated to identify potential improvements in or alternatives to the baseline waste retrieval methods. Communications with a variety of vendors are underway to identify improved methods that can be implemented at Hanford with little or no additional development. Commercially available retrieval methods will be evaluated by a combination of testing and system-level cost estimation. Current progress toward developing waste simulants for testing ACTR candidate methods is reported; the simulants are designed to model 4 different types of tank waste. Simulant recipes are given for wet sludge, hardpan/dried sludge,hard saltcake, and soft saltcake. Comparisons of the waste and simulant properties are documented in this report

Fracture Simulation of Highly Crosslinked Polymer Networks: Triglyceride-Based Adhesives

Science.gov (United States)

Lorenz, Christian; Stevens, Mark; Wool, Richard

2003-03-01

The ACRES program at the U. of Delaware has shown that triglyceride oils derived from plants are a favorable alternative to the traditional adhesives. The triglyceride networks are formed from an initial mixture of styrene monomers, free-radical initiators and triglycerides. We have performed simulations to study the effect of physical composition and physical characteristics of the triglyceride network on the strength of triglyceride network. A coarse-grained, bead-spring model of the triglyceride system is used. The average triglyceride consists of 6 beads per chain, the styrenes are represented as a single bead and the initiators are two bead chains. The polymer network is formed using an off-lattice 3D Monte Carlo simulation, in which the initiators activate the styrene and triglyceride reactive sites and then bonds are randomly formed between the styrene and active triglyceride monomers producing a highly crosslinked polymer network. Molecular dynamics simulations of the network under tensile and shear strains were performed to determine the strength as a function of the network composition. The relationship between the network structure and its strength will also be discussed.

Sequential use of simulation and optimization in analysis and planning

Science.gov (United States)

Hans R. Zuuring; Jimmie D. Chew; J. Greg Jones

2000-01-01

Management activities are analyzed at landscape scales employing both simulation and optimization. SIMPPLLE, a stochastic simulation modeling system, is initially applied to assess the risks associated with a specific natural process occurring on the current landscape without management treatments, but with fire suppression. These simulation results are input into...

A retrodictive stochastic simulation algorithm

International Nuclear Information System (INIS)

Vaughan, T.G.; Drummond, P.D.; Drummond, A.J.

2010-01-01

In this paper we describe a simple method for inferring the initial states of systems evolving stochastically according to master equations, given knowledge of the final states. This is achieved through the use of a retrodictive stochastic simulation algorithm which complements the usual predictive stochastic simulation approach. We demonstrate the utility of this new algorithm by applying it to example problems, including the derivation of likely ancestral states of a gene sequence given a Markovian model of genetic mutation.

OMV mission simulator

Science.gov (United States)

Cok, Keith E.

1989-01-01

The Orbital Maneuvering Vehicle (OMV) will be remotely piloted during rendezvous, docking, or proximity operations with target spacecraft from a ground control console (GCC). The real-time mission simulator and graphics being used to design a console pilot-machine interface are discussed. A real-time orbital dynamics simulator drives the visual displays. The dynamics simulator includes a J2 oblate earth gravity model and a generalized 1962 rotating atmospheric and drag model. The simulator also provides a variable-length communication delay to represent use of the Tracking and Data Relay Satellite System (TDRSS) and NASA Communications (NASCOM). Input parameter files determine the graphics display. This feature allows rapid prototyping since displays can be easily modified from pilot recommendations. A series of pilot reviews are being held to determine an effective pilot-machine interface. Pilots fly missions with nominal to 3-sigma dispersions in translational or rotational axes. Console dimensions, switch type and layout, hand controllers, and graphic interfaces are evaluated by the pilots and the GCC simulator is modified for subsequent runs. Initial results indicate a pilot preference for analog versus digital displays and for two 3-degree-of-freedom hand controllers.

Promotion of initiated cells by radiation-induced cell inactivation.

Science.gov (United States)

Heidenreich, W F; Paretzke, H G

2008-11-01

Cells on the way to carcinogenesis can have a growth advantage relative to normal cells. It has been hypothesized that a radiation-induced growth advantage of these initiated cells might be induced by an increased cell replacement probability of initiated cells after inactivation of neighboring cells by radiation. Here Monte Carlo simulations extend this hypothesis for larger clones: The effective clonal expansion rate decreases with clone size. This effect is stronger for the two-dimensional than for the three-dimensional situation. The clones are irregular, far from a circular shape. An exposure-rate dependence of the effective clonal expansion rate could come in part from a minimal recovery time of the initiated cells for symmetric cell division.

Trends in simulation and the Krsko full scope simulator

International Nuclear Information System (INIS)

Boire, R.; Chatlani, M.

1998-01-01

The nuclear power plant simulation industry is a fast-paced industry yielding continual development as a result of innovations in technology and customer requirements. This paper will discuss the current trends in simulator requirements, the status of simulation technology and the expected future developments, particularly in the context of the NPP Krsko full scope simulator. CAE Electronics has been awarded the contract for the design, construction, integration, testing and commissioning of the NPP Krsko full scope simulator (KFSS) by Nuklearna elektrarna Krsko (NEK). KFSS, as an integral part of the NPP Krsko Modernization plan, has been the subject of an extensive procurement process. KFSS will also take into account the steam generator replacement and plant uprate projects which will be delivered to provide initial training in the modernized plant configuration. As a result, the completed KFSS will meet NEK's goals for reliable training in safe plant operation as well as the licensing requirements of the Slovenian Nuclear Safety Administration. KFSS will be a state-of-the-art facility featuring high fidelity process and control models, proven technology and superior maintainability that will push the envelope of traditional simulator uses. In addition to serving its role as a high quality training vehicle, KFSS will be used for engineering purposes including procedure development and validation, optimization of plant operation and study and validation of plant modifications. KFSS models will be built for the most part with CAE's ROSE TM toolset. ROSE, is a component-based, visual programming environment for the creation, testing, integration and management of simulator models and supporting virtual panels. The NSSS will be simulated using the ANTHEM two-phase drift flux model, while be simulated using the COMET two-group, three-dimensional model. Software design and testing will be supported by an extensive series of quality procedures throughout the software

Micellar polymerization: Computer simulations by dissipative particle dynamics.

Science.gov (United States)

Shupanov, Ruslan; Chertovich, Alexander; Kos, Pavel

2018-07-15

Nowadays, micellar polymerization is widely used in different fields of industry and research, including modern living polymerization technique. However, this process has many variables and there is no comprehensive model to describe all features. This research presents simulation methodology which describes key properties of such reactions to take a guide through a variety of their modifications. Dissipative particle dynamics is used in addition to Monte Carlo scheme to simulate initiation, propagation, and termination events. Influence of initiation probability and different termination processes on final conversion and molecular-weight distribution are presented. We demonstrate that prolonged initiation leads to increasing in polymer average molecular weight, and surface termination events play major role in conversion limitation, in comparison with recombination. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Accomplishments and challenges of surgical simulation.

Science.gov (United States)

Satava, R M

2001-03-01

For nearly a decade, advanced computer technologies have created extraordinary educational tools using three-dimensional (3D) visualization and virtual reality. Pioneering efforts in surgical simulation with these tools have resulted in a first generation of simulators for surgical technical skills. Accomplishments include simulations with 3D models of anatomy for practice of surgical tasks, initial assessment of student performance in technical skills, and awareness by professional societies of potential in surgical education and certification. However, enormous challenges remain, which include improvement of technical fidelity, standardization of accurate metrics for performance evaluation, integration of simulators into a robust educational curriculum, stringent evaluation of simulators for effectiveness and value added to surgical training, determination of simulation application to certification of surgical technical skills, and a business model to implement and disseminate simulation successfully throughout the medical education community. This review looks at the historical progress of surgical simulators, their accomplishments, and the challenges that remain.

Global peatland initiation driven by regionally asynchronous warming.

Science.gov (United States)

Morris, Paul J; Swindles, Graeme T; Valdes, Paul J; Ivanovic, Ruza F; Gregoire, Lauren J; Smith, Mark W; Tarasov, Lev; Haywood, Alan M; Bacon, Karen L

2018-05-08

Widespread establishment of peatlands since the Last Glacial Maximum represents the activation of a globally important carbon sink, but the drivers of peat initiation are unclear. The role of climate in peat initiation is particularly poorly understood. We used a general circulation model to simulate local changes in climate during the initiation of 1,097 peatlands around the world. We find that peat initiation in deglaciated landscapes in both hemispheres was driven primarily by warming growing seasons, likely through enhanced plant productivity, rather than by any increase in effective precipitation. In Western Siberia, which remained ice-free throughout the last glacial period, the initiation of the world's largest peatland complex was globally unique in that it was triggered by an increase in effective precipitation that inhibited soil respiration and allowed wetland plant communities to establish. Peat initiation in the tropics was only weakly related to climate change, and appears to have been driven primarily by nonclimatic mechanisms such as waterlogging due to tectonic subsidence. Our findings shed light on the genesis and Holocene climate space of one of the world's most carbon-dense ecosystem types, with implications for understanding trajectories of ecological change under changing future climates.

Initial assessment of tumor tracking with a gimbaled linac system in clinical circumstances: A patient simulation study

International Nuclear Information System (INIS)

Depuydt, Tom; Poels, Kenneth; Verellen, Dirk; Engels, Benedikt; Collen, Christine; Haverbeke, Chloe; Gevaert, Thierry; Buls, Nico; Van Gompel, Gert; Reynders, Truus; Duchateau, Michael; Tournel, Koen; Boussaer, Marlies; Steenbeke, Femke; Vandenbroucke, Frederik; De Ridder, Mark

2013-01-01

Purpose: To have an initial assessment of the Vero Dynamic Tracking workflow in clinical circumstances and quantify the performance of the tracking system, a simulation study was set up on 5 lung and liver patients. Methods and materials: The preparatory steps of a tumor tracking treatment, based on fiducial markers implanted in the tumor, were executed allowing pursuit of the tumor with the gimbaled linac and monitoring X-rays acquisition, however, without activating the 6 MV beam. Data were acquired on workflow time-efficiency, tracking accuracy and imaging exposure. Results: The average time between the patient entering the treatment room and the first treatment field was about 9 min. The time for building the correlation model was 3.2 min. Tracking errors of 0.55 and 0.95 mm (1σ) were observed in PAN/TILT direction and a 2D range of 3.08 mm. A skin dose was determined of 0.08 mGy/image, with a source-to-skin distance of 900 mm and kV exposure of 1 mAs. On average 1.8 mGy/min kV skin dose was observed for 1 Hz monitoring. Conclusion: The Vero tracking solution proved to be fully functional and showed performance comparable with other real-time tracking systems

Crack initiation modeling of a directionally-solidified nickel-base superalloy

Science.gov (United States)

Gordon, Ali Page

crystal plasticity model was used to simulate the material behavior in the L and T orientations. The constitutive model was implemented in ABAQUS and a parameter estimation scheme was developed to obtain the material constants. A physically-based model was developed for correlating crack initiation life based on the experimental life data and predictions are made using the crack initiation model. Assuming a unique relationship between the damage fraction and cycle fraction with respect to cycles to crack initiation for each damage mode, the total crack initiation life has been represented in terms of the individual damage components (fatigue, creep-fatigue, creep, and oxidation-fatigue) observed at the end state of crack initiation.

Improved performance of maternal-fetal medicine staff after maternal cardiac arrest simulation-based training.

Science.gov (United States)

Fisher, Nelli; Eisen, Lewis A; Bayya, Jyothshna V; Dulu, Alina; Bernstein, Peter S; Merkatz, Irwin R; Goffman, Dena

2011-09-01

To determine the impact of simulation-based maternal cardiac arrest training on performance, knowledge, and confidence among Maternal-Fetal Medicine staff. Maternal-Fetal Medicine staff (n = 19) participated in a maternal arrest simulation program. Based on evaluation of performance during initial simulations, an intervention was designed including: basic life support course, advanced cardiac life support pregnancy modification lecture, and simulation practice. Postintervention evaluative simulations were performed. All simulations included a knowledge test, confidence survey, and debriefing. A checklist with 9 pregnancy modification (maternal) and 16 critical care (25 total) tasks was used for scoring. Postintervention scores reflected statistically significant improvement. Maternal-Fetal Medicine staff demonstrated statistically significant improvement in timely initiation of cardiopulmonary resuscitation (120 vs 32 seconds, P = .042) and cesarean delivery (240 vs 159 seconds, P = .017). Prompt cardiopulmonary resuscitation initiation and pregnancy modifications application are critical in maternal and fetal survival during cardiac arrest. Simulation is a useful tool for Maternal-Fetal Medicine staff to improve skills, knowledge, and confidence in the management of this catastrophic event. Published by Mosby, Inc.

Initial computer modeling of WIPP [Waste Isolation Pilot Plant] underground ventilation system, September 1985--March 1986

International Nuclear Information System (INIS)

Sethi, S.

1986-11-01

Provision of a good ventilation system has been and continues to be a major priority here of those responsible for its design, management, and operation. As an ongoing effort in this direction, development of computer simulated models for the system was initiated in September, 1985. It was decided to utilize Dravo's 'MINEVENT' computer program for this purpose. Accordingly, initial computer models of the mine's ventilation system have been developed for various modes of operation. Specifically, they include: Simulation of the current ventilation system, and Simulation of the designed ventilation system for modes: mine construction mode/shift, waste storage mode/shift, and air reversal mode. 5 figs

COTRANSA simulation of Chinshan unit one generator load rejection test

International Nuclear Information System (INIS)

Wu, C.H.

1984-01-01

A simulation of the plant behavior during a BWR generator load rejection transient using Exxon Nuclear Company's COTRANSA code is presented in this paper. The results are compared to measurements obtained by Taiwan Power Company during a generator load rejection transient, initiated at full power condition, which was one of the Chinshan Unit 1 initial cycle startup tests. Good agreement between the COTRANSA predicted and the measured values, indicates that the COTRANSA code can simulate this transient satisfactorily

Nonlinear Multiscale Modeling of 3D Woven Fiber Composites under Ballistic Loading

Science.gov (United States)

2013-07-11

estimates (Nemat-Nasser 1993). We denote the fiber and matrix Young’s modulus, shear modulus and Poisson ratio is denoted as Ef ,ν f ,µ f and Em,νm...2008) which need tracking of cracks explicitly with restrictions on periodicity are impractical for complex, dynamic loading of fiber reinforced ...and Rotem 1973) is often used to initiate the damage modes in fiber reinforced composite. According to the criteria damage accumulation starts when

Shock wave interaction with turbulence: Pseudospectral simulations

International Nuclear Information System (INIS)

Buckingham, A.C.

1986-01-01

Shock waves amplify pre-existing turbulence. Shock tube and shock wave boundary layer interaction experiments provide qualitative confirmation. However, shock pressure, temperature, and rapid transit complicate direct measurement. Computational simulations supplement the experimental data base and help isolate the mechanisms responsible. Simulations and experiments, particularly under reflected shock wave conditions, significantly influence material mixing. In these pseudospectral Navier-Stokes simulations the shock wave is treated as either a moving (tracked or fitted) domain boundary. The simulations assist development of code mix models. Shock Mach number and pre-existing turbulence intensity initially emerge as key parameters. 20 refs., 8 figs

Two-dimensional simulations of magnetically-driven instabilities

International Nuclear Information System (INIS)

Peterson, D.; Bowers, R.; Greene, A.E.; Brownell, J.

1986-01-01

A two-dimensional Eulerian MHD code is used to study the evolution of magnetically-driven instabilities in cylindrical geometry. The code incorporates an equation of state, resistivity, and radiative cooling model appropriate for an aluminum plasma. The simulations explore the effects of initial perturbations, electrical resistivity, and radiative cooling on the growth and saturation of the instabilities. Comparisons are made between the 2-D simulations, previous 1-D simulations, and results from the Pioneer experiments of the Los Alamos foil implosion program

The effective χ parameter in polarizable polymeric systems: One-loop perturbation theory and field-theoretic simulations.

Science.gov (United States)

Grzetic, Douglas J; Delaney, Kris T; Fredrickson, Glenn H

2018-05-28

We derive the effective Flory-Huggins parameter in polarizable polymeric systems, within a recently introduced polarizable field theory framework. The incorporation of bead polarizabilities in the model self-consistently embeds dielectric response, as well as van der Waals interactions. The latter generate a χ parameter (denoted χ̃) between any two species with polarizability contrast. Using one-loop perturbation theory, we compute corrections to the structure factor Sk and the dielectric function ϵ^(k) for a polarizable binary homopolymer blend in the one-phase region of the phase diagram. The electrostatic corrections to S(k) can be entirely accounted for by a renormalization of the excluded volume parameter B into three van der Waals-corrected parameters B AA , B AB , and B BB , which then determine χ̃. The one-loop theory not only enables the quantitative prediction of χ̃ but also provides useful insight into the dependence of χ̃ on the electrostatic environment (for example, its sensitivity to electrostatic screening). The unapproximated polarizable field theory is amenable to direct simulation via complex Langevin sampling, which we employ here to test the validity of the one-loop results. From simulations of S(k) and ϵ^(k) for a system of polarizable homopolymers, we find that the one-loop theory is best suited to high concentrations, where it performs very well. Finally, we measure χ̃N in simulations of a polarizable diblock copolymer melt and obtain excellent agreement with the one-loop theory. These constitute the first fully fluctuating simulations conducted within the polarizable field theory framework.

Initial frequency shift of large amplitude plasma wave, 2

International Nuclear Information System (INIS)

Yamanaka, K.; Sugihara, R.; Ohsawa, Y.; Kamimura, T.

1979-07-01

A nonlinear complex frequency shift of the ion acoustic wave in the initial phase defined by 0 0 and ωsub(s)/k as long as ωsub(s) >> γsub( l), where phi 0 , ωsub(s), γsub( l) and t sub(c) are the initial value of the potential, the frequency of the wave, the linear Landau damping coefficient and the time for the first minimum of the amplitude oscillation, respectively. A simulation study is also carried out. The results confirm the validity of the theory. (author)

Fractographic observations of cleavage initiation in the ductile-brittle transition region of a reactor-pressure-vessel steel

International Nuclear Information System (INIS)

Rosenfield, A.R.; Shetty, D.K.; Skidmore, A.J.

1983-01-01

This note reports the results of a fractographic study conducted on a group of 1T compact fracture toughness specimens of a heavy-section A508 steel denoted TSE6 tested in the ductile-brittle transition region (22 and 82 0 C). The fatigue-precracked specimens were loaded at a rapid rate (760 or 550 mm per second) to promote cleavage-crack growth and lower-bound toughness behavior. All specimens experienced unstable cleavage fracture prior to reaching a maximum in the load displacement curve. Some ductile crack growth occurred in half of the specimens. The objective of fractographic examinations was to understand the observed statistical variations in cleavage initiation by (a) locating the origins of unstable cleavage fracture in the vicinity of the fatigue-precrack or ductilerupture crack fronts, (b) identifying microstructural features associated with the triggering of cleavage, and (c) documenting characteristic fracture surface dimensions such as the extent of stable-crack growth prior to unstable cleavage (Δα) and the distance of the cleavage origin from the ductilerupture front, /chi/ (or fatigue-crack front when Δα = 0)

Evaluation of initiation behavior of stress corrosion cracking for type 316L stainless steel in high temperature water. Behavior of crack initiation and effects of distribution of plastic strain on crack initiation

International Nuclear Information System (INIS)

Miura, Yasufumi; Miyahara, Yuichi; Kako, Kenji; Sato, Masaru

2011-01-01

It is known that the initiation of stress corrosion cracking (SCC) in components such as the reactor core shroud and primary loop re-circulation piping made of L-grade stainless steel is affected by the properties of surface work hardened layer. Therefore, it is important to clarify the effect of the hardened layer on SCC initiation behavior. In this study, creviced bent beam (CBB) test using specimens made of Type 316L stainless steel with controlled distribution of surface work hardened layer was conducted in a simulated BWR environment in order to evaluate the effect of the controlled layer on SCC initiation behavior. The results obtained are as follows; (1) Micro intergranular SCC of low carbon stainless steel was initiated in 50 hours. (2) In this SCC test, it was found that only micro cracks whose depths were smaller than 50 μm were observed until 250 hours and cracks whose depths were larger than 50 μm were observed after 500 hours. (3) SCC was initiated preferentially on the region with high plastic strain gradient in the specimen with controlled distribution of work hardened layer. (author)

Delivering Insight The History of the Accelerated Strategic Computing Initiative

Energy Technology Data Exchange (ETDEWEB)

Larzelere II, A R

2007-01-03

The history of the Accelerated Strategic Computing Initiative (ASCI) tells of the development of computational simulation into a third fundamental piece of the scientific method, on a par with theory and experiment. ASCI did not invent the idea, nor was it alone in bringing it to fruition. But ASCI provided the wherewithal - hardware, software, environment, funding, and, most of all, the urgency - that made it happen. On October 1, 2005, the Initiative completed its tenth year of funding. The advances made by ASCI over its first decade are truly incredible. Lawrence Livermore, Los Alamos, and Sandia National Laboratories, along with leadership provided by the Department of Energy's Defense Programs Headquarters, fundamentally changed computational simulation and how it is used to enable scientific insight. To do this, astounding advances were made in simulation applications, computing platforms, and user environments. ASCI dramatically changed existing - and forged new - relationships, both among the Laboratories and with outside partners. By its tenth anniversary, despite daunting challenges, ASCI had accomplished all of the major goals set at its beginning. The history of ASCI is about the vision, leadership, endurance, and partnerships that made these advances possible.

Debris flow-induced topographic changes: effects of recurrent debris flow initiation.

Science.gov (United States)

Chen, Chien-Yuan; Wang, Qun

2017-08-12

Chushui Creek in Shengmu Village, Nantou County, Taiwan, was analyzed for recurrent debris flow using numerical modeling and geographic information system (GIS) spatial analysis. The two-dimensional water flood and mudflow simulation program FLO-2D were used to simulate debris flow induced by rainfall during typhoon Herb in 1996 and Mindulle in 2004. Changes in topographic characteristics after the debris flows were simulated for the initiation of hydrological characteristics, magnitude, and affected area. Changes in topographic characteristics included those in elevation, slope, aspect, stream power index (SPI), topographic wetness index (TWI), and hypsometric curve integral (HI), all of which were analyzed using GIS spatial analysis. The results show that the SPI and peak discharge in the basin increased after a recurrence of debris flow. The TWI was higher in 2003 than in 2004 and indicated higher potential of landslide initiation when the slope of the basin was steeper. The HI revealed that the basin was in its mature stage and was shifting toward the old stage. Numerical simulation demonstrated that the parameters' mean depth, maximum depth, affected area, mean flow rate, maximum flow rate, and peak flow discharge were increased after recurrent debris flow, and peak discharge occurred quickly.

Effects of Initial Particle Distribution on an Energetic Dispersal of Particles

Science.gov (United States)

Rollin, Bertrand; Ouellet, Frederick; Koneru, Rahul; Garno, Joshua; Durant, Bradford

2017-11-01

Accurate predictions of the late time solid particle cloud distribution ensuing an explosive dispersal of particles is an extremely challenging problem for compressible multiphase flow simulations. The source of this difficulty is twofold: (i) The complex sequence of events taking place. Indeed, as the blast wave crosses the surrounding layer of particles, compaction occurs shortly before particles disperse radially at high speed. Then, during the dispersion phase, complex multiphase interactions occurs between particles and detonation products. (ii) Precise characterization of the explosive and particle distribution is virtually impossible. In this numerical experiment, we focus on the sensitivity of late time particle cloud distributions relative to carefully designed initial distributions, assuming the explosive is well described. Using point particle simulations, we study the case of a bed of glass particles surrounding an explosive. Constraining our simulations to relatively low initial volume fractions to prevent reaching of the close packing limit, we seek to describe qualitatively and quantitatively the late time dependency of a solid particle cloud on its distribution before the energy release of an explosive. This work was supported by the U.S. DoE, NNSA, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

Plant specific basic principle simulator as a first step to plant specific full scope simulator

International Nuclear Information System (INIS)

Krajnc, B.; Pribozic, F.; Novsak, M.

1996-01-01

Nuklearna Elektrarna Krsko (NEK) decided to enhance the quality and scope of initial training of NEK technical personnel, mainly in so called Phase 1 and 2 of training for licensed personnel. This training is a prerequisite for further training on the full scope simulator for future operators and is also given to larger number of engineers, working in different important areas where thorough knowledge of nuclear technology and plant systems is required. Due to that it was decided that plant specific Basis Principle Simulators (BPS) should be developed. The other important reason for such decision was an indication that NEK specific full scope simulator will have to be purchased. Based on that it was concluded that BPS should serve as a good opportunity to learn about the state of the art approaches in the modeling area, to see in which direction development of software in conjunction with state of the art hardware is going and in particular to the extent possible verify the existence of required plant documentation in support BPS and later plant specific full scope simulator. In this paper the scope of NEK BPS simulation, experience in initial data gathering, experience with know-how transfer based on direct involvement of NEK and Izobrazevalni Center za Jedrsko Tehnnologijo (ICJT) personnel in modeling of instrumentation and control will be presented. Lessons learned, particularly in light of coming project for NEK full scope simulator, will also be addressed. The future use of the BPS in the NEK training programs will be described. It can be concluded that due to very complex technology, phase approaches in training of key NEK technical personnel, the development of NEK plant specific BPS is justifiable, regardless of the fact that NEK will also obtain specific full scope simulator. It has to be pointed out that BPS can not be supplement for plant specific full scope simulator, due to number of reasons discussed in the paper. (author)

An advanced analysis method of initial orbit determination with too short arc data

Science.gov (United States)

Li, Binzhe; Fang, Li

2018-02-01

This paper studies the initial orbit determination (IOD) based on space-based angle measurement. Commonly, these space-based observations have short durations. As a result, classical initial orbit determination algorithms give poor results, such as Laplace methods and Gauss methods. In this paper, an advanced analysis method of initial orbit determination is developed for space-based observations. The admissible region and triangulation are introduced in the method. Genetic algorithm is also used for adding some constraints of parameters. Simulation results show that the algorithm can successfully complete the initial orbit determination.

Denotational World-indexed Logical Relations and Friends

DEFF Research Database (Denmark)

Thamsborg, Jacob Junker

and solve the fundamental type-worlds circularity by metric-space theory. This approach scales to state-of-theart step-indexed techniques and permits unrestricted relational reasoning by the use of so-called Bohr relations. Along the way, we develop auxiliary theory; most notably a generalized version...... of separation logic with assertion variables. In particular, we give criteria for when standard, unary separation logic proofs lift to the binary setting. Phrased dierently, given a module-dependent client and a standard separation logic proof of its correctness, we ponder the default question of representation...

Denotational semantics in Synthetic Guarded Domain Theory

DEFF Research Database (Denmark)

Paviotti, Marco

In functional programming, features such as recursion, recursive types and general references are central. To define semantics of this kind of languages one needs to come up with certain definitions which may be non-trivial to show well-defined. This is because they are circular. Domain theory has...... been used to solve this kind of problems for specific languages, unfortunately, this technique does not scale for more featureful languages, which prevented it from being widely used. Step-indexing is a more general technique that has been used to break circularity of definitions. The idea is to tweak...... the definition by adding a well- founded structure that gives a handle for recursion. Guarded dependent Type Theory (gDTT) is a type theory which implements step-indexing via a unary modality used to guard recursive definitions. Every circular definition is well-defined as long as the recursive variable...

Denotational Aspects of Untyped Normalization by Evaluation

DEFF Research Database (Denmark)

Filinski, Andrzej; Rohde, Henning Korsholm

2005-01-01

of soundness (the output term, if any, is in normal form and ß-equivalent to the input term); identification (ß-equivalent terms are mapped to the same result); and completeness (the function is defined for all terms that do have normal forms). We also show how the semantic construction enables a simple yet...... formal correctness proof for the normalization algorithm, expressed as a functional program in an ML-like, call-by-value language. Finally, we generalize the construction to produce an infinitary variant of normal forms, namely Böhm trees. We show that the three-part characterization of correctness...

Denotational semantics for guarded dependent type theory

DEFF Research Database (Denmark)

Bizjak, Aleš; Møgelberg, Rasmus Ejlers

2018-01-01

We present a new model of Guarded Dependent Type Theory (GDTT), a type theory with guarded recursion and multiple clocks in which one can program with, and reason about coinductive types. Productivity of recursively defined coinductive programs and proofs is encoded in types using guarded recursion......, crucial for programming with coinductive types, types must be interpreted as presheaves orthogonal to the object of clocks. In the case of dependent types, this translates to a unique lifting condition similar to the one found in homotopy theoretic models of type theory. Since the universes defined...... by inclusions of clock variable contexts commute on the nose with type operations on the universes....

A denotational theory of synchronous reactive systems

OpenAIRE

Benveniste , Albert; Le Guernic , Paul; Sorel , Yves; Sorine , Michel

1992-01-01

International audience; In this paper, systems which interact permanently with their environments are considered. Such systems are encountered, for instance, in real-time control or signal processing systems, C3-systems, and man-machine interfaces, to mention just a few cases. The design and implementation of such systems require a concurrent programming language which can be used to verify and synthesize the synchronization mechanisms, and to perform transformations of the concurrent source ...

Simulation Architecture for Modelling Interaction Between User and Elbow-articulated Exoskeleton

NARCIS (Netherlands)

Kruif, B.J. de; Schmidhauser, E.; Stadler, K.S.; O'Sullivan, L.W.

2017-01-01

The aim of our work is to improve the existing user-exoskeleton models by introducing a simulation architecture that can simulate its dynamic interaction, thereby altering the initial motion of the user. A simulation architecture is developed that uses the musculoskeletal models from OpenSim, and

Adherence and perceptions regarding simulation training in undergraduate health Sciences

Directory of Open Access Journals (Sweden)

Fernando Perpétuo Elias

Full Text Available BACKGROUND: Simulation techniques are spreading rapidly in medicine. Suc h resources are increasingly concentrated in Simulation Laboratories. The MSRP-USP is structuring such a laboratory and is interested in the prevalence of individual initiatives that could be centralized there. The MSRP-USP currently has five full-curriculum courses in the health sciences: Medicine, Speech Therapy, Physical Therapy, Nutrition, and Occupational Therapy, all consisting of core disciplines. GOAL: To determine the prevalence of simulation techniques in the regular courses at MSRP-USP. METHODS: Coordinators of disciplines in the various courses were interviewed using a specifically designed semi-structured questionnaire, and all the collected data were stored in a dedicated database. The disciplines were grouped according to whether they used (GI or did not use (GII simulation resources. RESULTS AND DISCUSSION: 256 disciplines were analyzed, of which only 18.3% used simulation techniques, varying according to course: Medicine (24.7.3%, Occupational Therapy (23.0%, Nutrition (15.9%, Physical Therapy (9.8%, and Speech Therapy (9.1%. Computer simulation programs predominated (42.5% in all five courses. The resources were provided mainly by MSRP-USP (56.3%, with additional funding coming from other sources based on individual initiatives. The same pattern was observed for maintenance. There was great interest in centralizing the resources in the new Simulation Laboratory in order to facilitate maintenance, but there was concern about training and access to the material. CONCLUSIONS: 1 The MSRP-USP simulation resources show low complexity and are mainly limited to computer programs; 2 Use of simulation varies according to course, and is most prevalent in Medicine; 3 Resources are scattered across several locations, and their acquisition and maintenance depend on individual initiatives rather than central coordination or curricular guidelines

Initiation devices, initiation systems including initiation devices and related methods

Energy Technology Data Exchange (ETDEWEB)

Daniels, Michael A.; Condit, Reston A.; Rasmussen, Nikki; Wallace, Ronald S.

2018-04-10

Initiation devices may include at least one substrate, an initiation element positioned on a first side of the at least one substrate, and a spark gap electrically coupled to the initiation element and positioned on a second side of the at least one substrate. Initiation devices may include a plurality of substrates where at least one substrate of the plurality of substrates is electrically connected to at least one adjacent substrate of the plurality of substrates with at least one via extending through the at least one substrate. Initiation systems may include such initiation devices. Methods of igniting energetic materials include passing a current through a spark gap formed on at least one substrate of the initiation device, passing the current through at least one via formed through the at least one substrate, and passing the current through an explosive bridge wire of the initiation device.

Equilibrium sampling by reweighting nonequilibrium simulation trajectories.

Science.gov (United States)

Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin

2016-03-01

Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems.

A risk-informed approach to the assessment of DHC initiation in pressure tubes

International Nuclear Information System (INIS)

Sahoo, A.K.; Pandey, M.D.

2009-01-01

The delayed hydride cracking (DHC) of pressure tubes is a serious form of degradation in the reactor core. Flaws in pressure tubes generated by fretting or any other mechanism are potential stress raisers that could become sites of DHC initiation under right circumstances. CSA standard N285.8 recommends deterministic and probabilistic procedures for the assessment of potential for DHC initiation from planar flaws. The deterministic method is simple, but it lacks a risk-informed basis for the assessment. A full probabilistic method based on simulations is tedious to implement. This paper presents an innovative, semi-probabilistic method that bridges the gap between a simple deterministic analysis and complex simulations. In the proposed method, the deterministic assessment criterion of CSA N285.8 standard is calibrated to specified target probabilities of DHC initiation using the concept of partial factors. The main advantage of the proposed approach is that it provides a practical, risk-informed basis for DHC initiation assessment while retaining the simplicity of the deterministic method. (author)

Computer-simulation study of a disordered classical spin system in one dimension with long-range anisotropic ferromagnetic interactions

Science.gov (United States)

Romano, S.

1992-01-01

The present paper considers a classical system, consisting of n-component unit vectors (n=2 or 3), associated with a one-dimensional lattice \\{uk||k∈openZ\\}, and interacting via a translationally invariant pair potential of the long-range, ferromagnetic and anisotropic form W=Wjk=-ɛ||j-k||-2(auj,nuk,n +b tsumλuk,λ denotes the Cartesian components of the unit vectors. According to the available rigorous results, the system disorders at all finite temperatures when a=b, or n=3, a=0, and possesses an ordering transition at finite temperature when b=0. Approximate arguments and simulation results suggest that the isotropic models (a=b) produce a transition to a low-temperature phase with infinite susceptibility and power-law decay of the correlation function. If this is true, the available correlation inequalities entail that it also happens in the anisotropic but O(2)-invariant case n=3, b=0. We report here Monte Carlo calculations for this latter potential model; simulation results were found to be consistent with this conjecture, and to suggest that T*c=0.65+/-0.01.

Predicting a contact's sensitivity to initial conditions using metrics of frictional coupling

International Nuclear Information System (INIS)

Flicek, Robert C.; Hills, David A.; Brake, Matthew Robert W.

2016-01-01

This paper presents a method for predicting how sensitive a frictional contact’s steady-state behavior is to its initial conditions. Previous research has proven that if a contact is uncoupled, i.e. if slip displacements do not influence the contact pressure distribution, then its steady-state response is independent of initial conditions, but if the contact is coupled, the steady-state response depends on initial conditions. In this paper, two metrics for quantifying coupling in discrete frictional systems are examined. These metrics suggest that coupling is dominated by material dissimilarity due to Dundurs’ composite material parameter β when β ≥ 0.2, but geometric mismatch becomes the dominant source of coupling for smaller values of β. Based on a large set of numerical simulations with different contact geometries, material combinations, and friction coefficients, a contact’s sensitivity to initial conditions is found to be correlated with the product of the coupling metric and the friction coefficient. For cyclic shear loading, this correlation is maintained for simulations with different contact geometries, material combinations, and friction coefficients. Furthermore, for cyclic bulk loading, the correlation is only maintained when the contact edge angle is held constant.

Improved fourth-year medical student clinical decision-making performance as a resuscitation team leader after a simulation-based curriculum.

Science.gov (United States)

Ten Eyck, Raymond P; Tews, Matthew; Ballester, John M; Hamilton, Glenn C

2010-06-01

To determine the impact of simulation-based instruction on student performance in the role of emergency department resuscitation team leader. A randomized, single-blinded, controlled study using an intention to treat analysis. Eighty-three fourth-year medical students enrolled in an emergency medicine clerkship were randomly allocated to two groups differing only by instructional format. Each student individually completed an initial simulation case, followed by a standardized curriculum of eight cases in either group simulation or case-based group discussion format before a second individual simulation case. A remote coinvestigator measured eight objective performance end points using digital recordings of all individual simulation cases. McNemar chi2, Pearson correlation, repeated measures multivariate analysis of variance, and follow-up analysis of variance were used for statistical evaluation. Sixty-eight students (82%) completed both initial and follow-up individual simulations. Eight students were lost from the simulation group and seven from the discussion group. The mean postintervention case performance was significantly better for the students allocated to simulation instruction compared with the group discussion students for four outcomes including a decrease in mean time to (1) order an intravenous line; (2) initiate cardiac monitoring; (3) order initial laboratory tests; and (4) initiate blood pressure monitoring. Paired comparisons of each student's initial and follow-up simulations demonstrated significant improvement in the same four areas, in mean time to order an abdominal radiograph and in obtaining an allergy history. A single simulation-based teaching session significantly improved student performance as a team leader. Additional simulation sessions provided further improvement compared with instruction provided in case-based group discussion format.

Comparison of tritium concentrations in rainwater, simulated infiltrating water, and groundwater

International Nuclear Information System (INIS)

Ishii, Yoshiyuki; Saito, Masaaki; Imaizumi, Hiroshi; Kato, Norio; Kitaoka, Koichi

2014-01-01

The tritium concentration in initial groundwater(i.e., freshly infiltrating rainwater) is necessary for groundwater dating. We collected simulated infiltrating water as the initial groundwater and examined its characteristics for tritium concentration. First, in Tokyo, the tritium concentration of simulated infiltrating water was compared with that of rainwater, atmospheric moisture, groundwater, spring water, and sap water. While rainwater, atmospheric moisture, and simulated infiltrating water remarkably changed month-to-month or with every rainfall event, groundwater and spring water were nearly constant throughout the year. Second, we collected the simulated infiltrating water monthly at four sampling sites widely dispersed across Japan(i.e., Sapporo, Niigata, Tokyo, and Matsuyama) from 2004 to 2010. Sapporo and Niigata showed high tritium concentrations as compared with the relatively low concentrations in Tokyo and Matsuyama. These results indicate that we can obtain annual maximum and minimum concentrations at each site, and that we can estimate the tritium concentration in initial groundwater at each site by using a mixing model composed of these maximum and minimum concentrations. (author)

Investigating H₂ Sorption in a Fluorinated Metal-Organic Framework with Small Pores Through Molecular Simulation and Inelastic Neutron Scattering.

Science.gov (United States)

Forrest, Katherine A; Pham, Tony; Georgiev, Peter A; Pinzan, Florian; Cioce, Christian R; Unruh, Tobias; Eckert, Juergen; Space, Brian

2015-07-07

Simulations of H2 sorption were performed in a metal-organic framework (MOF) consisting of Zn(2+) ions coordinated to 1,2,4-triazole and tetrafluoroterephthalate ligands (denoted [Zn(trz)(tftph)] in this work). The simulated H2 sorption isotherms reported in this work are consistent with the experimental data for the state points considered. The experimental H2 isosteric heat of adsorption (Qst) values for this MOF are approximately 8.0 kJ mol(-1) for the considered loading range, which is in the proximity of those determined from simulation. The experimental inelastic neutron scattering (INS) spectra for H2 in [Zn(trz)(tftph)] reveal at least two peaks that occur at low energies, which corresponds to high barriers to rotation for the respective sites. The most favorable sorption site in the MOF was identified from the simulations as sorption in the vicinity of a metal-coordinated H2O molecule, an exposed fluorine atom, and a carboxylate oxygen atom in a confined region in the framework. Secondary sorption was observed between the fluorine atoms of adjacent tetrafluoroterephthalate ligands. The H2 molecule at the primary sorption site in [Zn(trz)(tftph)] exhibits a rotational barrier that exceeds that for most neutral MOFs with open-metal sites according to an empirical phenomenological model, and this was further validated by calculating the rotational potential energy surface for H2 at this site.

Molecular dynamics modeling on the role of initial void geometry in a thin aluminum film under uniaxial tension

International Nuclear Information System (INIS)

Cui, Yi; Chen, Zengtao

2015-01-01

The effect of initial void geometry on damage progression in a thin aluminum film under uniaxial load is studied via molecular dynamics (MD) method. The embedded voids are with different initial geometries regarding shape, porosity and intervoid ligament distance (ILD). Major simulations are run upon twelve MD geometries with each containing 8–27 million atoms. The corresponding stress–strain relation is monitored during the microstructure evolution of the specimens. The critical stress to trigger the dislocation emission is found in line with the prediction of the Lubarda model. The simulation results reveal that the initial void geometry has substantial impact on the stress–strain relation especially for a specimen with larger initial porosity. (paper)

Component-based framework for subsurface simulations

International Nuclear Information System (INIS)

Palmer, B J; Fang, Yilin; Hammond, Glenn; Gurumoorthi, Vidhya

2007-01-01

Simulations in the subsurface environment represent a broad range of phenomena covering an equally broad range of scales. Developing modelling capabilities that can integrate models representing different phenomena acting at different scales present formidable challenges both from the algorithmic and computer science perspective. This paper will describe the development of an integrated framework that will be used to combine different models into a single simulation. Initial work has focused on creating two frameworks, one for performing smooth particle hydrodynamics (SPH) simulations of fluid systems, the other for performing grid-based continuum simulations of reactive subsurface flow. The SPH framework is based on a parallel code developed for doing pore scale simulations, the continuum grid-based framework is based on the STOMP (Subsurface Transport Over Multiple Phases) code developed at PNNL Future work will focus on combining the frameworks together to perform multiscale, multiphysics simulations of reactive subsurface flow

Computer simulation of high energy displacement cascades

International Nuclear Information System (INIS)

Heinisch, H.L.

1990-01-01

A methodology developed for modeling many aspects of high energy displacement cascades with molecular level computer simulations is reviewed. The initial damage state is modeled in the binary collision approximation (using the MARLOWE computer code), and the subsequent disposition of the defects within a cascade is modeled with a Monte Carlo annealing simulation (the ALSOME code). There are few adjustable parameters, and none are set to physically unreasonable values. The basic configurations of the simulated high energy cascades in copper, i.e., the number, size and shape of damage regions, compare well with observations, as do the measured numbers of residual defects and the fractions of freely migrating defects. The success of these simulations is somewhat remarkable, given the relatively simple models of defects and their interactions that are employed. The reason for this success is that the behavior of the defects is very strongly influenced by their initial spatial distributions, which the binary collision approximation adequately models. The MARLOWE/ALSOME system, with input from molecular dynamics and experiments, provides a framework for investigating the influence of high energy cascades on microstructure evolution. (author)

Laboratory Facility for Simulating Solar Wind Sails

International Nuclear Information System (INIS)

Funaki, Ikkoh; Ueno, Kazuma; Oshio, Yuya; Ayabe, Tomohiro; Horisawa, Hideyuki; Yamakawa, Hiroshi

2008-01-01

Magnetic sail (MagSail) is a deep space propulsion system, in which an artificial magnetic cavity captures the energy of the solar wind to propel a spacecraft in the direction leaving the sun. For a scale-model experiment of the plasma flow of MagSail, we employed a magnetoplasmadynamic arcjet as a solar wind simulator. It is observed that a plasma flow from the solar wind simulator reaches a quasi-steady state of about 0.8 ms duration after a transient phase when initiating the discharge. During this initial phase of the discharge, a blast-wave was observed to develop radially in a vacuum chamber. When a solenoidal coil (MagSail scale model) is immersed into the quasi-steady flow where the velocity is 45 km/s, and the number density is 10 19 m-3, a bow shock as well as a magnetic cavity were formed in front of the coil. As a result of the interaction between the plasma flow and the magnetic cavity, the momentum of the simulated solar wind is decreased, and it is found from the thrust measurement that the solar wind momentum is transferred to the coil simulating MagSail.

Fluorescent Metal-Organic Framework (MOF) as a Highly Sensitive and Quickly Responsive Chemical Sensor for the Detection of Antibiotics in Simulated Wastewater.

Science.gov (United States)

Zhu, Xian-Dong; Zhang, Kun; Wang, Yu; Long, Wei-Wei; Sa, Rong-Jian; Liu, Tian-Fu; Lü, Jian

2018-02-05

A Zn(II)-based fluorescent metal-organic framework (MOF) was synthesized and applied as a highly sensitive and quickly responsive chemical sensor for antibiotic detection in simulated wastewater. The fluorescent chemical sensor, denoted FCS-1, exhibited enhanced fluorescence derived from its highly ordered, 3D MOF structure as well as excellent water stability in the practical pH range of simulated antibiotic wastewater (pH = 3.0-9.0). Remarkably, FCS-1 was able to effectively detect a series of sulfonamide antibiotics via photoinduced electron transfer that caused detectable fluorescence quenching, with fairly low detection limits. Two influences impacting measurements related to wastewater treatment and water quality monitoring, the presence of heavy-metal ions and the pH of solutions, were studied in terms of fluorescence quenching, which was nearly unaffected in sulfonamide-antibiotic detection. Additionally, the effective detection of sulfonamide antibiotics was rationalized by the theoretical computation of the energy bands of sulfonamide antibiotics, which revealed a good match between the energy bands of FCS-1 and sulfonamide antibiotics, in connection with fluorescence quenching in this system.

Initial verification and validation of RAZORBACK - A research reactor transient analysis code

Energy Technology Data Exchange (ETDEWEB)

Talley, Darren G. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

2015-09-01

This report describes the work and results of the initial verification and validation (V&V) of the beta release of the Razorback code. Razorback is a computer code designed to simulate the operation of a research reactor (such as the Annular Core Research Reactor (ACRR)) by a coupled numerical solution of the point reactor kinetics equations, the energy conservation equation for fuel element heat transfer, and the mass, momentum, and energy conservation equations for the water cooling of the fuel elements. This initial V&V effort was intended to confirm that the code work to-date shows good agreement between simulation and actual ACRR operations, indicating that the subsequent V&V effort for the official release of the code will be successful.

Care initiation area yields dramatic results.

Science.gov (United States)

2009-03-01

The ED at Gaston Memorial Hospital in Gastonia, NC, has achieved dramatic results in key department metrics with a Care Initiation Area (CIA) and a physician in triage. Here's how the ED arrived at this winning solution: Leadership was trained in and implemented the Kaizen method, which eliminates redundant or inefficient process steps. Simulation software helped determine additional space needed by analyzing arrival patterns and other key data. After only two days of meetings, new ideas were implemented and tested.

Influence of the initial conditions for the numerical simulation of two-phase slug flow

Energy Technology Data Exchange (ETDEWEB)

Pachas Napa, Alex A.; Morales, Rigoberto E.M.; Medina, Cesar D. Perea

2010-07-01

Multiphase flows in pipelines commonly show several patterns depending on the flow rate, geometry and physical properties of the phases. In oil production, the slug flow pattern is the most common among the others. This flow pattern is characterized by an intermittent succession in space and time of an aerated liquid slug and an elongated gas bubble with a liquid film. Slug flow is studied through the slug tracking model described as one-dimensional and Lagrangian frame referenced. In the model, the mass and the momentum balance equations are applied in control volumes constituted by the gas bubble and the liquid slug. Initial conditions must be determined, which need to reproduce the intermittence of the flow pattern. These initial conditions are given by a sequence of flow properties for each unit cell. Properties of the unit cell in initial conditions should reflect the intermittence, for which they can be analyzed in statistical terms. Therefore, statistical distributions should be obtained for the slug flow variables. Distributions are complemented with the mass balance and the bubble design model. The objective of the present work is to obtain initial conditions for the slug tracking model that reproduce a better adjustment of the fluctuating properties for different pipe inclinations (horizontal, vertical or inclined). The numerical results are compared with experimental data obtained by PFG/FEM/UNICAMP for air-water flow at 0 deg, 45 deg and 90 deg and good agreement is observed. (author)

Signature of protein adaptation to warm deep sea environments: the case of Initiation Factor 6 studied by molecular simulation and neutron scattering

International Nuclear Information System (INIS)

Calligari, Paolo

2008-01-01

The protein Initiation Factor 6 (IF6) takes part in the protein synthesis regulation of several organisms. It was also found in archeaebacteria such as Methanococcus jannaschii which lives in deep-seas near hydrothermal vents where temperature reaches 80 C and pressure is between 250 bar and 500 bar. The aim of this work was to study for the first time dynamical and structural properties of IF6 produced by M. jannaschii and comparing them with those of the IF6 homologue present in Saccharomyces cerevisiae which lives at 'normal' environmental conditions (27 C and 1 bar). Molecular simulation gave here new insights into the adaptation of these two proteins to their respective physiological conditions and showed that the latter induced similar dynamical and structural properties: in their respective 'natural' conditions, IF6s show very similar structural fluctuations and the characteristic relaxation times which define their dynamical properties shows similar changes when comparing unfavorable conditions to physiological ones. The creation of these corresponding states between the two homologues has been interpreted by the fractional Brownian dynamics model and by a novel method for the characterization of protein secondary structures. The latter is presented here in detail together with some examples of other applications. Experimental data obtained from quasi-elastic neutron scattering seemed to support the results obtained by molecular simulations. (author) [fr

"Gaze Leading": Initiating Simulated Joint Attention Influences Eye Movements and Choice Behavior

Science.gov (United States)

Bayliss, Andrew P.; Murphy, Emily; Naughtin, Claire K.; Kritikos, Ada; Schilbach, Leonhard; Becker, Stefanie I.

2013-01-01

Recent research in adults has made great use of the gaze cuing paradigm to understand the behavior of the follower in joint attention episodes. We implemented a gaze leading task to investigate the initiator--the other person in these triadic interactions. In a series of gaze-contingent eye-tracking studies, we show that fixation dwell time upon…

High-Order Weno Simulations of Three-Dimensional Reshocked Richtmyer-Meshkov Instability to Late Times: Dynamics, Dependence on Initial Conditions, and Comparisons to Experimental Data

Energy Technology Data Exchange (ETDEWEB)

Schilling, O; Latini, M

2010-01-12

The dynamics of the reshocked multi-mode Richtmyer-Meshkov instability is investigated using 513 x 257{sup 2} three-dimensional ninth-order weighted essentially nonoscillatory shock-capturing simulations. A two-mode initial perturbation with superposed random noise is used to model the Mach 1.5 air/SF{sub 6} Vetter-Sturtevant shock tube experiment. The mass fraction and enstrophy isosurfaces, and density cross-sections are utilized to show the detailed flow structure before, during, and after reshock. It is shown that the mixing layer growth agrees well with the experimentally measured growth rate before and after reshock. The post-reshock growth rate is also in good agreement with the prediction of the Mikaelian model. A parametric study of the sensitivity of the layer growth to the choice of amplitudes of the short and long wavelength initial interfacial perturbation is also presented. Finally, the amplification effects of reshock are quantified using the evolution of the turbulent kinetic energy and turbulent enstrophy spectra, as well as the evolution of the baroclinic enstrophy production, buoyancy production, and shear production terms in the enstrophy and turbulent kinetic transport equations.

Effect of Heterogeneity in Initial Geographic Distribution on Opinions’ Competitiveness

Directory of Open Access Journals (Sweden)

Alexander S. Balankin

2015-05-01

Full Text Available Spin dynamics on networks allows us to understand how a global consensus emerges out of individual opinions. Here, we are interested in the effect of heterogeneity in the initial geographic distribution of a competing opinion on the competitiveness of its own opinion. Accordingly, in this work, we studied the effect of spatial heterogeneity on the majority rule dynamics using a three-state spin model, in which one state is neutral. Monte Carlo simulations were performed on square lattices divided into square blocks (cells. Accordingly, one competing opinion was distributed uniformly among cells, whereas the spatial distribution of the rival opinion was varied from the uniform to heterogeneous, with the median-to-mean ratio in the range from 1 to 0. When the size of discussion group is odd, the uncommitted agents disappear completely after  3.30 ± 0.05 update cycles, and then the system evolves in a two-state regime with complementary spatial distributions of two competing opinions. Even so, the initial heterogeneity in the spatial distribution of one of the competing opinions causes a decrease of this opinion competitiveness. That is, the opinion with initially heterogeneous spatial distribution has less probability to win, than the opinion with the initially uniform spatial distribution, even when the initial concentrations of both opinions are equal. We found that although the time to consensus , the opinion’s recession rate is determined during the first 3.3 update cycles. On the other hand, we found that the initial heterogeneity of the opinion spatial distribution assists the formation of quasi-stable regions, in which this opinion is dominant. The results of Monte Carlo simulations are discussed with regard to the electoral competition of political parties.

The Australian Computational Earth Systems Simulator

Science.gov (United States)

Mora, P.; Muhlhaus, H.; Lister, G.; Dyskin, A.; Place, D.; Appelbe, B.; Nimmervoll, N.; Abramson, D.

2001-12-01

behaviour of earth systems. ACcESS represents a part of Australia's contribution to the APEC Cooperation for Earthquake Simulation (ACES) international initiative. Together with other national earth systems science initiatives including the Japanese Earth Simulator and US General Earthquake Model projects, ACcESS aims to provide a driver for scientific advancement and technological breakthroughs including: quantum leaps in understanding of earth evolution at global, crustal, regional and microscopic scales; new knowledge of the physics of crustal fault systems required to underpin the grand challenge of earthquake prediction; new understanding and predictive capabilities of geological processes such as tectonics and mineralisation.

Simulation of Second Harmonic Ultrasound Fields

DEFF Research Database (Denmark)

Du, Yigang; Jensen, Henrik; Jensen, Jørgen Arendt

2010-01-01

A non-linear ultrasound imaging simulation software should be capable of simulating the non-linear fields for any kind of transducer, focusing, apodization, and attenuation. At present, a major issue is the overlong simulation time of the non-linear software. An Angular Spectrum Approach (ASA......) using a quasi-linear approximation for solving the Westervelt equation can simulate the second harmonic pressure at any distance. Therefore, it shortens the execution time compared with the operator splitting method. The purpose of this paper is to implement the monochromatic solution for the second...... harmonic component based on ASA and Field II, and to compare with results from the simulation program Abersim. A linear array transducer with a center frequency of 4 MHz and 64 active elements is used as the transmitting source. The initial plane is 5 mm away from the transducer surface...

3D numerical simulations of multiphase continental rifting

Science.gov (United States)

Naliboff, J.; Glerum, A.; Brune, S.

2017-12-01

Observations of rifted margin architecture suggest continental breakup occurs through multiple phases of extension with distinct styles of deformation. The initial rifting stages are often characterized by slow extension rates and distributed normal faulting in the upper crust decoupled from deformation in the lower crust and mantle lithosphere. Further rifting marks a transition to higher extension rates and coupling between the crust and mantle lithosphere, with deformation typically focused along large-scale detachment faults. Significantly, recent detailed reconstructions and high-resolution 2D numerical simulations suggest that rather than remaining focused on a single long-lived detachment fault, deformation in this phase may progress toward lithospheric breakup through a complex process of fault interaction and development. The numerical simulations also suggest that an initial phase of distributed normal faulting can play a key role in the development of these complex fault networks and the resulting finite deformation patterns. Motivated by these findings, we will present 3D numerical simulations of continental rifting that examine the role of temporal increases in extension velocity on rifted margin structure. The numerical simulations are developed with the massively parallel finite-element code ASPECT. While originally designed to model mantle convection using advanced solvers and adaptive mesh refinement techniques, ASPECT has been extended to model visco-plastic deformation that combines a Drucker Prager yield criterion with non-linear dislocation and diffusion creep. To promote deformation localization, the internal friction angle and cohesion weaken as a function of accumulated plastic strain. Rather than prescribing a single zone of weakness to initiate deformation, an initial random perturbation of the plastic strain field combined with rapid strain weakening produces distributed normal faulting at relatively slow rates of extension in both 2D and

An educational initiative to improve medical student awareness about brain death.

Science.gov (United States)

Lewis, Ariane; Howard, Jonathan; Watsula-Morley, Amanda; Gillespie, Colleen

2018-04-01

Medical student knowledge about brain death determination is limited. We describe an educational initiative to improve medical student awareness about brain death and assess the impact of this initiative. Beginning in July 2016, students at our medical school were required to attend a 90-min brain death didactic and simulation session during their neurology clerkship. Students completed a test immediately before and after participating in the initiative. Of the 145 students who participated in this educational initiative between July 2016 and June 2017, 124 (86%) consented to have their data used for research purposes as part of a medical education registry. Students correctly answered a median of 53% of questions (IQR 47-58%) on the pretest and 86% of questions (IQR 78-89%) on the posttest (p initiative (18% of students were comfortable performing a brain death evaluation before the initiative and 86% were comfortable doing so after the initiative, p initiative and 76% were comfortable doing so after the initiative, p initiative, but awareness and comfort dealing with brain death improved significantly after this initiative. Copyright © 2018 Elsevier B.V. All rights reserved.

SIMULATING MAGNETIC FIELDS IN THE ANTENNAE GALAXIES

International Nuclear Information System (INIS)

Kotarba, H.; Karl, S. J.; Naab, T.; Johansson, P. H.; Lesch, H.; Dolag, K.; Stasyszyn, F. A.

2010-01-01

We present self-consistent high-resolution simulations of NGC 4038/4039 (the A ntennae galaxies ) including star formation, supernova feedback, and magnetic fields performed with the N-body/smoothed particle hydrodynamic (SPH) code GADGET, in which magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 10 -9 to 10 -4 G. At the time of the best match with the central region of the Antennae system, the magnetic field has been amplified by compression and shear flows to an equilibrium field value of ∼10 μG, independent of the initial seed field. These simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly nonlinear environment. We also discuss the relevance of the amplification effect for present-day magnetic fields in the context of hierarchical structure formation.

SPONTANEOUS INITIATION OF DETONATIONS IN WHITE DWARF ENVIRONMENTS: DETERMINATION OF CRITICAL SIZES

International Nuclear Information System (INIS)

Seitenzahl, Ivo R.; Meakin, Casey A.; Townsley, Dean M.; Truran, James W.; Lamb, Don Q.

2009-01-01

Some explosion models for Type Ia supernovae (SNe Ia), such as the gravitationally confined detonation (GCD) or the double detonation sub-Chandrasekhar (DDSC) models, rely on the spontaneous initiation of a detonation in the degenerate 12 C/ 16 O material of a white dwarf (WD). The length scales pertinent to the initiation of the detonation are notoriously unresolved in multidimensional stellar simulations, prompting the use of results of one-dimensional simulations at higher resolution, such as those performed for this work, as guidelines for deciding whether or not conditions reached in the higher dimensional full star simulations successfully would lead to the onset of a detonation. Spontaneous initiation relies on the existence of a suitable gradient in self-ignition (induction) times of the fuel, which we set up with a spatially localized nonuniformity of temperature-a hot spot. We determine the critical (smallest) sizes of such hot spots that still marginally result in a detonation in WD matter by integrating the reactive Euler equations with the hydrodynamics code FLASH. We quantify the dependences of the critical sizes of such hot spots on composition, background temperature, peak temperature, geometry, and functional form of the temperature disturbance, many of which were hitherto largely unexplored in the literature. We discuss the implications of our results in the context of modeling of SNe Ia.

Assessment of statistical education in Indonesia: Preliminary results and initiation to simulation-based inference

Science.gov (United States)

Saputra, K. V. I.; Cahyadi, L.; Sembiring, U. A.

2018-01-01

Start in this paper, we assess our traditional elementary statistics education and also we introduce elementary statistics with simulation-based inference. To assess our statistical class, we adapt the well-known CAOS (Comprehensive Assessment of Outcomes in Statistics) test that serves as an external measure to assess the student’s basic statistical literacy. This test generally represents as an accepted measure of statistical literacy. We also introduce a new teaching method on elementary statistics class. Different from the traditional elementary statistics course, we will introduce a simulation-based inference method to conduct hypothesis testing. From the literature, it has shown that this new teaching method works very well in increasing student’s understanding of statistics.

Investigation of practical initial attenuation image estimates in TOF-MLAA reconstruction for PET/MR

International Nuclear Information System (INIS)

Cheng, Ju-Chieh; Yaqub, Maqsood; Boellaard, Ronald; Salomon, Andre

2016-01-01

Purpose: Time-of-flight joint attenuation and activity positron emission tomography reconstruction requires additional calibration (scale factors) or constraints during or post-reconstruction to produce a quantitative μ-map. In this work, the impact of various initializations of the joint reconstruction was investigated, and the initial average mu-value (IAM) method was introduced such that the forward-projection of the initial μ-map is already very close to that of the reference μ-map, thus reducing/minimizing the offset (scale factor) during the early iterations of the joint reconstruction. Consequently, the accuracy and efficiency of unconstrained joint reconstruction such as time-of-flight maximum likelihood estimation of attenuation and activity (TOF-MLAA) can be improved by the proposed IAM method. Methods: 2D simulations of brain and chest were used to evaluate TOF-MLAA with various initial estimates which include the object filled with water uniformly (conventional initial estimate), bone uniformly, the average μ-value uniformly (IAM magnitude initialization method), and the perfect spatial μ-distribution but with a wrong magnitude (initialization in terms of distribution). 3D GATE simulation was also performed for the chest phantom under a typical clinical scanning condition, and the simulated data were reconstructed with a fully corrected list-mode TOF-MLAA algorithm with various initial estimates. The accuracy of the average μ-values within the brain, chest, and abdomen regions obtained from the MR derived μ-maps was also evaluated using computed tomography μ-maps as the gold-standard. Results: The estimated μ-map with the initialization in terms of magnitude (i.e., average μ-value) was observed to reach the reference more quickly and naturally as compared to all other cases. Both 2D and 3D GATE simulations produced similar results, and it was observed that the proposed IAM approach can produce quantitative μ-map/emission when the corrections

Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure

Science.gov (United States)

Bellan, Josette; Taskinoglu, Ezgi

2012-01-01

The simulation of high-pressure turbulent flows, where the pressure, p, is larger than the critical value, p(sub c), for the species under consideration, is relevant to a wide array of propulsion systems, e.g. gas turbine, diesel, and liquid rocket engines. Most turbulence models, however, have been developed for atmospheric-p turbulent flows. The difference between atmospheric-p and supercritical-p turbulence is that, in the former situation, the coupling between dynamics and thermodynamics is moderate to negligible, but for the latter it is very significant, and can dominate the flow characteristics. The reason for this stems from the mathematical form of the equation of state (EOS), which is the perfect-gas EOS in the former case, and the real-gas EOS in the latter case. For flows at supercritical pressure, p, the large eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas EOS. The equations use transport properties that depend on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid scale (SGS) fluxes, but also new SGS terms, each denoted as a correction. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations, and represent differences between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) that is the difference between the filtered divergence of the heat flux and the divergence of the heat flux computed as a function of the filtered flow field. In a previous study, there was only partial success in modeling the q-correction term, but in this innovation, success has been achieved by using a different modeling approach. This analysis, based on a temporal mixing layer Direct Numerical Simulation database, shows that the focus in modeling the q

Investigating H 2 Sorption in a Fluorinated Metal–Organic Framework with Small Pores Through Molecular Simulation and Inelastic Neutron Scattering

KAUST Repository

Forrest, Katherine A.

2015-07-07

© 2015 American Chemical Society. Simulations of H2 sorption were performed in a metal-organic framework (MOF) consisting of Zn²⁺ ions coordinated to 1,2,4-triazole and tetrafluoroterephthalate ligands (denoted [Zn(trz)(tftph)] in this work). The simulated H2 sorption isotherms reported in this work are consistent with the experimental data for the state points considered. The experimental H2 isosteric heat of adsorption (Qst) values for this MOF are approximately 8.0 kJ mol^-1 for the considered loading range, which is in the proximity of those determined from simulation. The experimental inelastic neutron scattering (INS) spectra for H2 in [Zn(trz)(tftph)] reveal at least two peaks that occur at low energies, which corresponds to high barriers to rotation for the respective sites. The most favorable sorption site in the MOF was identified from the simulations as sorption in the vicinity of a metal-coordinated H2O molecule, an exposed fluorine atom, and a carboxylate oxygen atom in a confined region in the framework. Secondary sorption was observed between the fluorine atoms of adjacent tetrafluoroterephthalate ligands. The H2 molecule at the primary sorption site in [Zn(trz)(tftph)] exhibits a rotational barrier that exceeds that for most neutral MOFs with open-metal sites according to an empirical phenomenological model, and this was further validated by calculating the rotational potential energy surface for H2 at this site. (Figure Presented).

Tokamak Simulation Code modeling of NSTX

International Nuclear Information System (INIS)

Jardin, S.C.; Kaye, S.; Menard, J.; Kessel, C.; Glasser, A.H.

2000-01-01

The Tokamak Simulation Code [TSC] is widely used for the design of new axisymmetric toroidal experiments. In particular, TSC was used extensively in the design of the National Spherical Torus eXperiment [NSTX]. The authors have now benchmarked TSC with initial NSTX results and find excellent agreement for plasma and vessel currents and magnetic flux loops when the experimental coil currents are used in the simulations. TSC has also been coupled with a ballooning stability code and with DCON to provide stability predictions for NSTX operation. TSC has also been used to model initial CHI experiments where a large poloidal voltage is applied to the NSTX vacuum vessel, causing a force-free current to appear in the plasma. This is a phenomenon that is similar to the plasma halo current that sometimes develops during a plasma disruption

Comparison of high-accuracy numerical simulations of black-hole binaries with stationary-phase post-Newtonian template waveforms for initial and advanced LIGO

International Nuclear Information System (INIS)

Boyle, Michael; Brown, Duncan A; Pekowsky, Larne

2009-01-01

We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the initial- and advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both initial and advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 post-Newtonian (pN) order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass (M ≤ 35 M o-dot ) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass η above this. This strategy always achieves overlaps within 0.3% of the optimum, for the data used here. For advanced LIGO we recommend a strategy using 3.5 pN templates up to M = 12 M o-dot , 2.0 pN templates up to M = 21 M o-dot , pseudo-4.0 pN templates up to 65 M o-dot , and 3.5 pN templates with unphysical η for higher masses. This strategy always achieves overlaps within 0.7% of the optimum for advanced LIGO.

Converging on the Initial Mass Function of Stars

International Nuclear Information System (INIS)

Federrath, Christoph; Krumholz, Mark; Hopkins, Philip F.

2017-01-01

Understanding the origin of stellar masses—the initial mass function (IMF)— remains one of the most challenging problems in astrophysics. The IMF is a key ingredient for simulations of galaxy formation and evolution, and is used to calibrate star formation relations in extra-galactic observations. Modeling the IMF directly in hydrodynamical simulations has been attempted in several previous studies, but the most important processes that control the IMF remain poorly understood. This is because predicting the IMF from direct hydrodynamical simulations involves complex physics such as turbulence, magnetic fields, radiation feedback and mechanical feedback, all of which are difficult to model and the methods used have limitations in terms of accuracy and computational efficiency. Moreover, a physical interpretation of the simulated IMFs requires a numerically converged solution at high resolution, which has so far not been convincingly demonstrated. Here we present a resolution study of star cluster formation aimed at producing a converged IMF. We compare a set of magnetohydrodynamical (MHD) adaptive-mesh-refinement simulations with three different implementations of the thermodynamics of the gas: 1) with an isothermal equation of state (EOS), 2) with a polytropic EOS, and 3) with a simple stellar heating feedback model. We show that in the simulations with an isothermal or polytropic EOS, the number of stars and their mass distributions depend on the numerical resolution. By contrast, the simulations that employ the simple radiative feedback module demonstrate convergence in the number of stars formed and in their IMFs. (paper)

On the initiation of sustained slip-weakening ruptures by localized stresses

KAUST Repository

Galis, Martin

2014-12-10

Numerical simulations of dynamic earthquake rupture require an artificial initiation procedure, if they are not integrated in long-term earthquake cycle simulations. A widely applied procedure involves an \\'overstressed asperity\\', a localized region stressed beyond the static frictional strength. The physical properties of the asperity (size, shape and overstress) may significantly impact rupture propagation. In particular, to induce a sustained rupture the asperity size needs to exceed a critical value. Although criteria for estimating the critical nucleation size under linear slip-weakening friction have been proposed for 2-D and 3-D problems based on simplifying assumptions, they do not provide general rules for designing 3-D numerical simulations. We conduct a parametric study to estimate parameters of the asperity that minimize numerical artefacts (e.g. changes of rupture shape and speed, artificial supershear transition, higher slip-rate amplitudes). We examine the critical size of square, circular and elliptical asperities as a function of asperity overstress and background (off-asperity) stress. For a given overstress, we find that asperity area controls rupture initiation while asperity shape is of lesser importance. The critical area obtained from our numerical results contrasts with published theoretical estimates when background stress is low. Therefore, we derive two new theoretical estimates of the critical size under low background stress while also accounting for overstress. Our numerical results suggest that setting the asperity overstress and area close to their critical values eliminates strong numerical artefacts even when the overstress is large. We also find that properly chosen asperity size or overstress may significantly shorten the duration of the initiation. Overall, our results provide guidelines for determining the size of the asperity and overstress to minimize the effects of the forced initiation on the subsequent spontaneous

Decadal predictions of Southern Ocean sea ice : testing different initialization methods with an Earth-system Model of Intermediate Complexity

Science.gov (United States)

Zunz, Violette; Goosse, Hugues; Dubinkina, Svetlana

2013-04-01

The sea ice extent in the Southern Ocean has increased since 1979 but the causes of this expansion have not been firmly identified. In particular, the contribution of internal variability and external forcing to this positive trend has not been fully established. In this region, the lack of observations and the overestimation of internal variability of the sea ice by contemporary General Circulation Models (GCMs) make it difficult to understand the behaviour of the sea ice. Nevertheless, if its evolution is governed by the internal variability of the system and if this internal variability is in some way predictable, a suitable initialization method should lead to simulations results that better fit the reality. Current GCMs decadal predictions are generally initialized through a nudging towards some observed fields. This relatively simple method does not seem to be appropriated to the initialization of sea ice in the Southern Ocean. The present study aims at identifying an initialization method that could improve the quality of the predictions of Southern Ocean sea ice at decadal timescales. We use LOVECLIM, an Earth-system Model of Intermediate Complexity that allows us to perform, within a reasonable computational time, the large amount of simulations required to test systematically different initialization procedures. These involve three data assimilation methods: a nudging, a particle filter and an efficient particle filter. In a first step, simulations are performed in an idealized framework, i.e. data from a reference simulation of LOVECLIM are used instead of observations, herein after called pseudo-observations. In this configuration, the internal variability of the model obviously agrees with the one of the pseudo-observations. This allows us to get rid of the issues related to the overestimation of the internal variability by models compared to the observed one. This way, we can work out a suitable methodology to assess the efficiency of the

Electrical power system integrated thermal/electrical system simulation

International Nuclear Information System (INIS)

Freeman, W.E.

1992-01-01

This paper adds thermal properties to previously developed electrical Saber templates and incorporates these templates into a functional Electrical Power Subsystem (EPS) simulation. These combined electrical and thermal templates enable the complete and realistic simulation of a vehicle EPS on-orbit. Applications include on-orbit energy balance determinations for system load changes, initial array and battery EPS sizing for new EPS development, and array and battery technology trade studies. This effort proves the versatility of the Saber simulation program in handling varied and complex simulations accurately and in a reasonable amount of computer time. 9 refs

Simulation of robot manipulators

International Nuclear Information System (INIS)

Kress, R.L.; Babcock, S.M.; Bills, K.C.; Kwon, D.S.; Schoenwald, D.A.

1995-01-01

This paper describes Oak Ridge National Laboratory's development of an environment for the simulation of robotic manipulators. Simulation includes the modeling of kinematics, dynamics, sensors, actuators, control systems, operators, and environments. Models will be used for manipulator design, proposal evaluation, control system design and analysis, graphical preview of proposed motions, safety system development, and training. Of particular interest is the development of models for robotic manipulators having at least one flexible link. As a first application, models have been developed for the Pacific Northwest Laboratories' Flexible Beam Testbed which is a one-Degree-Of-Freedom, flexible arm with a hydraulic base actuator. Initial results show good agreement between model and experiment

Effects of Initial Stance of Quadruped Trotting on Walking Stability

Directory of Open Access Journals (Sweden)

Peisun Ma

2008-11-01

Full Text Available It is very important for quadruped walking machine to keep its stability in high speed walking. It has been indicated that moment around the supporting diagonal line of quadruped in trotting gait largely influences walking stability. In this paper, moment around the supporting diagonal line of quadruped in trotting gait is modeled and its effects on body attitude are analyzed. The degree of influence varies with different initial stances of quadruped and we get the optimal initial stance of quadruped in trotting gait with maximal walking stability. Simulation results are presented.

Choosing Wisely Imaging Recommendations: Initial Implementation in New England Emergency Departments

Directory of Open Access Journals (Sweden)

Ali S. Raja

2017-04-01

Full Text Available Introduction: In June 2016, the American College of Emergency Physicians (ACEP Emergency Quality Network began its Reduce Avoidable Imaging Initiative, designed to “reduce testing and imaging with low risk patients through the implementation of Choosing Wisely recommendations.” However, it is unknown whether New England emergency departments (ED have already implemented evidence-based interventions to improve adherence to ACEP Choosing Wisely recommendations related to imaging after their initial release in 2013. Our objective was to determine this, as well as whether provider-specific audit and feedback for imaging had been implemented in these EDs. Methods: This survey study was exempt from institutional review board review. In 2015, we mailed surveys to 195 hospital-affiliated EDs in all six New England states to determine whether they had implemented Choosing Wisely-focused interventions in 2014. Initial mailings included cover letters denoting the endorsement of each state’s ACEP chapter, and we followed up twice with repeat mailings to nonresponders. Data analysis included descriptive statistics and a comparison of state differences using Fisher’s exact test. Results: A total of 169/195 (87% of New England EDs responded, with all individual state response rates >80%. Overall, 101 (60% of responding EDs had implemented an intervention for at least one Choosing Wisely imaging scenario; 57% reported implementing a specific guideline/policy/clinical pathway and 28% reported implementing a computerized decision support system. The most common interventions were for chest computed tomography (CT in patients at low risk of pulmonary embolism (47% of EDs and head CT in patients with minor trauma (45% of EDs. In addition, 40% of EDs had implemented provider-specific audit and feedback, without significant interstate variation (range: 29-55%. Conclusion: One year after release of the ACEP Choosing Wisely recommendations, most New England EDs

Creating science simulations through Computational Thinking Patterns

Science.gov (United States)

Basawapatna, Ashok Ram

Computational thinking aims to outline fundamental skills from computer science that everyone should learn. As currently defined, with help from the National Science Foundation (NSF), these skills include problem formulation, logically organizing data, automating solutions through algorithmic thinking, and representing data through abstraction. One aim of the NSF is to integrate these and other computational thinking concepts into the classroom. End-user programming tools offer a unique opportunity to accomplish this goal. An end-user programming tool that allows students with little or no prior experience the ability to create simulations based on phenomena they see in-class could be a first step towards meeting most, if not all, of the above computational thinking goals. This thesis describes the creation, implementation and initial testing of a programming tool, called the Simulation Creation Toolkit, with which users apply high-level agent interactions called Computational Thinking Patterns (CTPs) to create simulations. Employing Computational Thinking Patterns obviates lower behavior-level programming and allows users to directly create agent interactions in a simulation by making an analogy with real world phenomena they are trying to represent. Data collected from 21 sixth grade students with no prior programming experience and 45 seventh grade students with minimal programming experience indicates that this is an effective first step towards enabling students to create simulations in the classroom environment. Furthermore, an analogical reasoning study that looked at how users might apply patterns to create simulations from high- level descriptions with little guidance shows promising results. These initial results indicate that the high level strategy employed by the Simulation Creation Toolkit is a promising strategy towards incorporating Computational Thinking concepts in the classroom environment.

Realistic and efficient 2D crack simulation

Science.gov (United States)

Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

2010-04-01

Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

Immersive visualization of rail simulation data.

Science.gov (United States)

2016-01-01

The prime objective of this project was to create scientific, immersive visualizations of a Rail-simulation. This project is a part of a larger initiative that consists of three distinct parts. The first step consists of performing a finite element a...

4D Simulation for Nuclear Power Plant Construction

International Nuclear Information System (INIS)

Jeong, Seo G.; Suh, Kune Y.

2006-01-01

For the timely and competitive response to rapidly changing energy environment at the turn of millennium, there is a desperate need to build the nuclear power plant (NPP) in the virtual reality of digital engineering prior to commissioning. To construct a NPP is a highly integrated, voluminous project. Verification of design and initial planning is prerequisite to construction to confirm optimal fabrication and high productivity. This paper presents the design feasibility by simulating the initial construction plan of NPP using four-dimensional (4D) simulation. The virtual reality method, using three dimensional (3D) computer-aided design (CAD) model, enables various designs in the project launching stage to be promptly and exactly previewed

Measurement of initial soil moisture conditions for purposes of rainfall simulation experiments

OpenAIRE

TEREZA, Davidová; VÁCLAV, David

2015-01-01

The research on rainfall-runoff processes has become even more important in recent decades with respect to both flood and drought events as well as to expected impacts of considered climate changes. It is researched in different ways and at different scales according to the purpose. The rainfall simulator developed at Department of Irrigation, Drainage and Landscape Engineering is being used for purposes of detail analysis of rainfall-runoff process in order to research infiltration process w...

Molecular dynamics simulation of bubble nucleation in explosive boiling

International Nuclear Information System (INIS)

Zou Yu; Chinese Academy of Sciences, Beijing; Huai Xiulan; Liang Shiqiang

2009-01-01

Molecular dynamics (MD) simulation is carried out for the bubble nucleation of liquid nitrogen in explosive boiling. The heat is transferred into the simulation system by rescaling the velocity of the molecules. The results indicate that the initial equilibrium temperature of liquid and molecular cluster size affect the energy conversion in the process of bubble nucleation. The potential energy of the system violently varies at the beginning of the bubble nucleation, and then varies around a fixed value. At the end of bubble nucleation, the potential energy of the system slowly increases. In the bubble nucleation of explosive boiling, the lower the initial equilibrium temperature, the larger the size of the molecular cluster, and the more the heat transferred into the system of the simulation cell, causing the increase potential energy in a larger range. (authors)

Numerical Simulation of a Tornado Generating Supercell

Science.gov (United States)

Proctor, Fred H.; Ahmad, Nashat N.; LimonDuparcmeur, Fanny M.

2012-01-01

The development of tornadoes from a tornado generating supercell is investigated with a large eddy simulation weather model. Numerical simulations are initialized with a sounding representing the environment of a tornado producing supercell that affected North Carolina and Virginia during the Spring of 2011. The structure of the simulated storm was very similar to that of a classic supercell, and compared favorably to the storm that affected the vicinity of Raleigh, North Carolina. The presence of mid-level moisture was found to be important in determining whether a supercell would generate tornadoes. The simulations generated multiple tornadoes, including cyclonic-anticyclonic pairs. The structure and the evolution of these tornadoes are examined during their lifecycle.

Initiation of Positive Streamers near Uncharged Ice Hydrometeors in the Thundercloud Field

Science.gov (United States)

Babich, L. P.; Bochkov, E. I.

2018-05-01

Since the threshold electric field required for breakdown of air is much higher than the maximum field strength measured in thunderstorm clouds, the problem of lightning initiation still remains unsolved. According to the popular hypothesis, lightning can be initiated by a streamer discharge in the field enhanced near a hydrometeor. To verify the adequacy of this hypothesis, the development of a positive streamer propagating along the thunderstorm electric field in the vicinity of an ice needle at an air pressure corresponding to an altitude of 5 km (which is typical of the lightning initiation conditions) was simulated numerically. The hydrometeor dimensions are determined at which streamers can be initiated at different strengths of the thunderstorm electric field.

Two-way coupling of magnetohydrodynamic simulations with embedded particle-in-cell simulations

Science.gov (United States)

Makwana, K. D.; Keppens, R.; Lapenta, G.

2017-12-01

We describe a method for coupling an embedded domain in a magnetohydrodynamic (MHD) simulation with a particle-in-cell (PIC) method. In this two-way coupling we follow the work of Daldorff et al. (2014) [19] in which the PIC domain receives its initial and boundary conditions from MHD variables (MHD to PIC coupling) while the MHD simulation is updated based on the PIC variables (PIC to MHD coupling). This method can be useful for simulating large plasma systems, where kinetic effects captured by particle-in-cell simulations are localized but affect global dynamics. We describe the numerical implementation of this coupling, its time-stepping algorithm, and its parallelization strategy, emphasizing the novel aspects of it. We test the stability and energy/momentum conservation of this method by simulating a steady-state plasma. We test the dynamics of this coupling by propagating plasma waves through the embedded PIC domain. Coupling with MHD shows satisfactory results for the fast magnetosonic wave, but significant distortion for the circularly polarized Alfvén wave. Coupling with Hall-MHD shows excellent coupling for the whistler wave. We also apply this methodology to simulate a Geospace Environmental Modeling (GEM) challenge type of reconnection with the diffusion region simulated by PIC coupled to larger scales with MHD and Hall-MHD. In both these cases we see the expected signatures of kinetic reconnection in the PIC domain, implying that this method can be used for reconnection studies.

Compactified cosmological simulations of the infinite universe

Science.gov (United States)

Rácz, Gábor; Szapudi, István; Csabai, István; Dobos, László

2018-06-01

We present a novel N-body simulation method that compactifies the infinite spatial extent of the Universe into a finite sphere with isotropic boundary conditions to follow the evolution of the large-scale structure. Our approach eliminates the need for periodic boundary conditions, a mere numerical convenience which is not supported by observation and which modifies the law of force on large scales in an unrealistic fashion. We demonstrate that our method outclasses standard simulations executed on workstation-scale hardware in dynamic range, it is balanced in following a comparable number of high and low k modes and, its fundamental geometry and topology match observations. Our approach is also capable of simulating an expanding, infinite universe in static coordinates with Newtonian dynamics. The price of these achievements is that most of the simulated volume has smoothly varying mass and spatial resolution, an approximation that carries different systematics than periodic simulations. Our initial implementation of the method is called StePS which stands for Stereographically projected cosmological simulations. It uses stereographic projection for space compactification and naive O(N^2) force calculation which is nevertheless faster to arrive at a correlation function of the same quality than any standard (tree or P3M) algorithm with similar spatial and mass resolution. The N2 force calculation is easy to adapt to modern graphics cards, hence our code can function as a high-speed prediction tool for modern large-scale surveys. To learn about the limits of the respective methods, we compare StePS with GADGET-2 running matching initial conditions.

Compactified Cosmological Simulations of the Infinite Universe

Science.gov (United States)

Rácz, Gábor; Szapudi, István; Csabai, István; Dobos, László

2018-03-01

We present a novel N-body simulation method that compactifies the infinite spatial extent of the Universe into a finite sphere with isotropic boundary conditions to follow the evolution of the large-scale structure. Our approach eliminates the need for periodic boundary conditions, a mere numerical convenience which is not supported by observation and which modifies the law of force on large scales in an unrealistic fashion. We demonstrate that our method outclasses standard simulations executed on workstation-scale hardware in dynamic range, it is balanced in following a comparable number of high and low k modes and, its fundamental geometry and topology match observations. Our approach is also capable of simulating an expanding, infinite universe in static coordinates with Newtonian dynamics. The price of these achievements is that most of the simulated volume has smoothly varying mass and spatial resolution, an approximation that carries different systematics than periodic simulations. Our initial implementation of the method is called StePS which stands for Stereographically Projected Cosmological Simulations. It uses stereographic projection for space compactification and naive O(N^2) force calculation which is nevertheless faster to arrive at a correlation function of the same quality than any standard (tree or P3M) algorithm with similar spatial and mass resolution. The N2 force calculation is easy to adapt to modern graphics cards, hence our code can function as a high-speed prediction tool for modern large-scale surveys. To learn about the limits of the respective methods, we compare StePS with GADGET-2 running matching initial conditions.

Beam Simulations for IRE and Driver-Status and Strategy

International Nuclear Information System (INIS)

Friedman, A.; Grote, D.P.; Lee, E.P.; Sonnendrucker, E.

2000-01-01

The methods and codes employed in the U.S. Heavy Ion Fusion program to simulate the beams in an Integrated Research Experiments (IRE) facility and a fusion driver are presented in overview. A new family of models incorporating accelerating module impedance, multi-beam, and self-magnetic effects is described, and initial WARP3d particle simulations of beams using these models are presented. Finally, plans for streamlining the machine-design simulation sequence, and for simulating beam dynamics from the source to the target in a consistent and comprehensive manner, are described

Characterization and reaction behavior of ferrocyanide simulants and Hanford Site high-level ferrocyanide waste

International Nuclear Information System (INIS)

Jeppson, D.W.; Simpson, B.C.

1994-02-01

Nonradioactive waste simulants and initial ferrocyanide tank waste samples were characterized to assess potential safety concerns associated with ferrocyanide high-level radioactive waste stored at the Hanford Site in underground single-shell tanks (SSTs). Chemical, physical, thermodynamic, and reaction properties of the waste simulants were determined and compared to properties of initial samples of actual ferrocyanide wastes presently in the tanks. The simulants were shown to not support propagating reactions when subjected to a strong ignition source. The simulant with the greatest ferrocyanide concentration was shown to not support a propagating reaction that would involve surrounding waste because of its high water content. Evaluation of dried simulants indicated a concentration limit of about 14 wt% disodium mononickel ferrocyanide, below which propagating reactions could not occur in the ambient temperature bulk tank waste. For postulated localized hot spots where dried waste is postulated to be at an initial temperature of 130 C, a concentration limit of about 13 wt% disodium mononickel ferrocyanide was determined, below which propagating reactions could not occur. Analyses of initial samples of the presently stored ferrocyanide waste indicate that the waste tank ferrocyanide concentrations are considerably lower than the limit for propagation for dry waste and that the water content is near that of the as-prepared simulants. If the initial trend continues, it will be possible to show that runaway ferrocyanide reactions are not possible under present tank conditions. The lower ferrocyanide concentrations in actual tank waste may be due to tank waste mixing and/or degradation from radiolysis and/or hydrolysis, which may have occurred over approximately 35 years of storage

Simulations of Shock Wave Interaction with a Particle Cloud

Science.gov (United States)

Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Annamalai, Subramanian; Balachandar, S.'Bala'

2016-11-01

Simulations of a shock wave interacting with a cloud of particles are performed in an attempt to understand similar phenomena observed in dispersal of solid particles under such extreme environment as an explosion. We conduct numerical experiments in which a particle curtain fills only 87% of the shock tube from bottom to top. As such, the particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In this study, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. In these simulations we use a Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. Measurements of particle dispersion are made at different initial volume fractions of the particle cloud. A detailed analysis of the evolution of the particle curtain with respect to the initial conditions is presented. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.

Particle simulations in toroidal geometry

International Nuclear Information System (INIS)

Aydemir, A.Y.

1992-09-01

A computational tool to be used in kinetic simulations of toroidal plasmas is being developed. The initial goal of the project is to develop an electrostatic gyrokinetic model for studying transport and stability problems in tokamaks. In this brief report, preliminary results from the early stages of this effort are presented

Agent-based Simulation of the Maritime Domain

Directory of Open Access Journals (Sweden)

O. Vaněk

2010-01-01

Full Text Available In this paper, a multi-agent based simulation platform is introduced that focuses on legitimate and illegitimate aspects of maritime traffic, mainly on intercontinental transport through piracy afflicted areas. The extensible architecture presented here comprises several modules controlling the simulation and the life-cycle of the agents, analyzing the simulation output and visualizing the entire simulated domain. The simulation control module is initialized by various configuration scenarios to simulate various real-world situations, such as a pirate ambush, coordinated transit through a transport corridor, or coastal fishing and local traffic. The environmental model provides a rich set of inputs for agents that use the geo-spatial data and the vessel operational characteristics for their reasoning. The agent behavior model based on finite state machines together with planning algorithms allows complex expression of agent behavior, so the resulting simulation output can serve as a substitution for real world data from the maritime domain.

Simulation and beam line experiments for the superconducting ECR ion source VENUS

International Nuclear Information System (INIS)

Todd, Damon S.; Leitner, Daniela; Grote, David P.; Lyneis, ClaudeM.

2007-01-01

The particle-in-cell code Warp has been enhanced to incorporate both two- and three-dimensional sheath extraction models giving Warp the capability of simulating entire ion beam transport systems including the extraction of beams from plasma sources. In this article we describe a method of producing initial ion distributions for plasma extraction simulations in electron cyclotron resonance (ECR) ion sources based on experimentally measured sputtering on the source biased disc. Using this initialization method, we present preliminary results for extraction and transport simulations of an oxygen beam and compare them with experimental beam imaging on a quartz viewing plate for the superconducting ECR ion source VENUS

Evaluation of clustering statistics with N-body simulations

International Nuclear Information System (INIS)

Quinn, T.R.

1986-01-01

Two series of N-body simulations are used to determine the effectiveness of various clustering statistics in revealing initial conditions from evolved models. All the simulations contained 16384 particles and were integrated with the PPPM code. One series is a family of models with power at only one wavelength. The family contains five models with the wavelength of the power separated by factors of √2. The second series is a family of all equal power combinations of two wavelengths taken from the first series. The clustering statistics examined are the two point correlation function, the multiplicity function, the nearest neighbor distribution, the void probability distribution, the distribution of counts in cells, and the peculiar velocity distribution. It is found that the covariance function, the nearest neighbor distribution, and the void probability distribution are relatively insensitive to the initial conditions. The distribution of counts in cells show a little more sensitivity, but the multiplicity function is the best of the statistics considered for revealing the initial conditions

Positive Wigner functions render classical simulation of quantum computation efficient.

Science.gov (United States)

Mari, A; Eisert, J

2012-12-07

We show that quantum circuits where the initial state and all the following quantum operations can be represented by positive Wigner functions can be classically efficiently simulated. This is true both for continuous-variable as well as discrete variable systems in odd prime dimensions, two cases which will be treated on entirely the same footing. Noting the fact that Clifford and Gaussian operations preserve the positivity of the Wigner function, our result generalizes the Gottesman-Knill theorem. Our algorithm provides a way of sampling from the output distribution of a computation or a simulation, including the efficient sampling from an approximate output distribution in the case of sampling imperfections for initial states, gates, or measurements. In this sense, this work highlights the role of the positive Wigner function as separating classically efficiently simulable systems from those that are potentially universal for quantum computing and simulation, and it emphasizes the role of negativity of the Wigner function as a computational resource.

Simulations of laser thrombolysis

Energy Technology Data Exchange (ETDEWEB)

Chapyak, E.J.; Godwin, R.P.

1999-03-01

The authors have shown that bubble expansion and collapse near the interface between two materials with modest property differences produces jet-like interpenetration of the two materials. The bubble dynamics at a water-viscous fluid interface is compared with that at the interface of water with a weak elastic-plastic material. The authors find that, despite rather similar behavior during bubble growth and the initial portion of bubble collapse, the terminal jetting behavior is quite different, even in direction. The elastic-plastic properties chosen realistically represent real and surrogate thrombus. Simulations using the elastic-plastic model quantitatively agree with laboratory thrombolysis mass removal experiments. In the earlier simulations of laboratory experiments, walls have been remote so as to not effect the dynamics. Here the authors present two-dimensional simulations of thrombolysis with water over elastic-plastic surrogate thrombus in a geometry representative of the clinical situation. The calculations include thin cylindrical elastic walls with properties and dimensions appropriate for arteries. The presence of these artery walls does not substantially change the interface jetting predicted in unconfined simulations.

A household-level sweet potato-based infant food to complement vitamin A supplementation initiatives.

Science.gov (United States)

Amagloh, Francis K; Hardacre, Allan; Mutukumira, Anthony N; Weber, Janet L; Brough, Louise; Coad, Jane

2012-10-01

Vitamin A deficiency (VAD) prevalence in Sub-Saharan Africa is high in spite of vitamin A supplementation programmes among children in most countries. Plant-based complementary foods remain the key source of nutrients in addition to breast milk for infants in lower income countries. Cereal-legume blends are superior in protein and energy densities compared with maize, millet or sorghum-only porridge. However, unfortified cereal-legume and cereal-only porridges are low in vitamin A. A household-level sweet potato-based infant food, rich in vitamin A, has been developed to complement vitamin A supplementation initiatives in Sub-Saharan Africa. A composite flour containing sweet potato, soybean, soybean oil and fishmeal was processed as complementary food by oven toasting (denoted oven-toasted ComFa). The oven-toasted ComFa and enriched Weanimix (processed from dehulled maize, dehulled soybean, groundnut and fishmeal) were assessed for suitability as complementary food based on the nutrient composition using specifications in the Codex Standard (CS) as a reference. The sweet potato-based formulation and enriched Weanimix met the energy, protein, fructose and fat specifications but barely met the amino acid score as indicated in the CS. However, only the oven-toasted ComFa met the calcium and almost half the vitamin A levels as specified in the CS. Oven-toasted ComFa was slightly lower in energy, protein and fat by a difference not greater than 4.0% but was higher by more than 100% in fructose and vitamin A levels. Therefore, the sweet potato-based complementary food is likely to support vitamin A supplementation initiatives in low-income countries better than the cereal-based formulation. © 2011 Blackwell Publishing Ltd.

Molecular dynamics simulation of carbon molecular sieve preparation for air separation

International Nuclear Information System (INIS)

Yaghoobpour, Elham; Ahmadpour, Ali; Farhadian, Nafiseh; Shariaty-Niassar, Mojtaba

2015-01-01

Carbon deposition process on activated carbon (AC) in order to produce carbon molecular sieve (CMS) was simulated using molecular dynamics simulation. The proposed activated carbon for simulation includes micropores with different characteristic diameters and lengths. Three different temperatures of 773 K, 973 K, and 1,273 K were selected to investigate the optimum deposition temperature. Simulation results show that the carbon deposition process at 973 K creates the best adsorbent structure. While at lower temperature some micropore openings are blocked with carbon atoms, at higher temperature the number of deposited carbons on the micropores does not change significantly. Also, carbon deposition process confirms the pseudo-second-order kinetic model with an endothermic behavior. To evaluate the sieving property of adsorbent products, nitrogen and oxygen adsorption on the initial and final adsorbent products are examined. Results show that there is not any considerable difference between the equilibrium adsorption amounts of nitrogen and oxygen on the initial and final adsorbents especially at low pressure (P<10 atm). Although, adsorption kinetics curves of these gases change significantly after the carbon deposition process in comparison with the initial sample. These observations indicate that the final adsorbent has high selectivity towards oxygen compared with the nitrogen, so it can be called a carbon molecular sieve. All simulated results are in good agreement with experiments

Molecular dynamics simulation of carbon molecular sieve preparation for air separation

Energy Technology Data Exchange (ETDEWEB)

Yaghoobpour, Elham; Ahmadpour, Ali; Farhadian, Nafiseh [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shariaty-Niassar, Mojtaba [University of Tehran, Tehran(Iran, Islamic Republic of)

2015-03-15

Carbon deposition process on activated carbon (AC) in order to produce carbon molecular sieve (CMS) was simulated using molecular dynamics simulation. The proposed activated carbon for simulation includes micropores with different characteristic diameters and lengths. Three different temperatures of 773 K, 973 K, and 1,273 K were selected to investigate the optimum deposition temperature. Simulation results show that the carbon deposition process at 973 K creates the best adsorbent structure. While at lower temperature some micropore openings are blocked with carbon atoms, at higher temperature the number of deposited carbons on the micropores does not change significantly. Also, carbon deposition process confirms the pseudo-second-order kinetic model with an endothermic behavior. To evaluate the sieving property of adsorbent products, nitrogen and oxygen adsorption on the initial and final adsorbent products are examined. Results show that there is not any considerable difference between the equilibrium adsorption amounts of nitrogen and oxygen on the initial and final adsorbents especially at low pressure (P<10 atm). Although, adsorption kinetics curves of these gases change significantly after the carbon deposition process in comparison with the initial sample. These observations indicate that the final adsorbent has high selectivity towards oxygen compared with the nitrogen, so it can be called a carbon molecular sieve. All simulated results are in good agreement with experiments.

Simulation of the Three Mile Island transient in Semiscale

International Nuclear Information System (INIS)

Larson, T.K.; Loomis, G.G.; Shumway, R.W.

1979-07-01

This report presents the results of a preliminary review and analysis of the data obtained from eight simulations of the Three Mile Island Unit 2 Nuclear Power Generating Station transient (March 28, 1979) that have been conducted in the Semiscale Mod-3 System. The Semiscale simulations of the Three Mile Island (TMI) transient were basically conducted from the same sequence of events as those recorded in the plant. System initial conditions representative of those in the TMI system were established and the transient was initiated by terminating steam generator feedwater and steam valve flow. The steam generator secondaries were drained to control primary to secondary heat transfer. The pressurizer power operated relief valve, pressurizer code safety valve, and core power trip were operated on system pressure. High pressure safety injection was activated for about one minute during the Semiscale simulations. In addition, both primary loop coolant pumps were shut off in the Semiscale simulation at the same time that the Three Mile Island loop 2A pump was shut off

Anticipation of the landing shock phenomenon in flight simulation

Science.gov (United States)

Mcfarland, Richard E.

1987-01-01

An aircraft landing may be described as a controlled crash because a runway surface is intercepted. In a simulation model the transition from aerodynamic flight to weight on wheels involves a single computational cycle during which stiff differential equations are activated; with a significant probability these initial conditions are unrealistic. This occurs because of the finite cycle time, during which large restorative forces will accompany unrealistic initial oleo compressions. This problem was recognized a few years ago at Ames Research Center during simulation studies of a supersonic transport. The mathematical model of this vehicle severely taxed computational resources, and required a large cycle time. The ground strike problem was solved by a described technique called anticipation equations. This extensively used technique has not been previously reported. The technique of anticipating a significant event is a useful tool in the general field of discrete flight simulation. For the differential equations representing a landing gear model stiffness, rate of interception and cycle time may combine to produce an unrealistic simulation of the continuum.

Inference of the Genetic Network Regulating Lateral Root Initiation in Arabidopsis thaliana

KAUST Repository

Muraro, D.; Voss, U.; Wilson, M.; Bennett, M.; Byrne, H.; De Smet, I.; Hodgman, C.; King, J.

2013-01-01

thaliana is stimulated by a cascade of regulators of which only the interactions of its initial elements have been identified. Using simulated gene expression data with known network topology, we compare the performance of inference algorithms, based

Experimental Investigation of Free Field and Shock-Initiated Implosion of Composite Structures

Science.gov (United States)

2017-02-06

knowledge by examining the pressure pulses emitted in collapse of carbon- fiber reinforced composite tubes and capturing full-field displacements...34:--::-::-=---= 1 2 R c R 0 G (1) Here, E1 and E2 are the longitudinal and transverse moduli, respectively, v12 and v21 are Poisson ’ s ratios of the two major...resin-rich interfibrillar region parallel to the reinforcing fibers . Fractured fibers in underlying plies are also seen in this micrograph, denoted

Use of simulators in severe accident management

International Nuclear Information System (INIS)

Evans, R.C.

1994-01-01

The U.S. nuclear utility industry is moving in a deliberate fashion through a coordinated industry severe accident working group to study and augment, where appropriate, the existing utility organizational and emergency planning structure to address accident and severe accident management. Full-scope simulators are used extensively to train licensed operators for their initial license examinations and continually thereafter in licensed operator requalification training and yearly examinations. The goal of the training (both initial and requalification) is to ensure that operators possess adequate knowledge, skills and abilities to prevent an event from progressing to core damage. The use of full-scope simulators in severe accident management training is in large part viewed by the industry as being premature. The working group study has not progressed to the point where the decision to employ full-scope simulators can be logically considered. It is not however premature to consider part-task or work station simulators as invaluable research tools to support the industry's study. These simulators could be employed, subject to limitations in the current state of knowledge regarding severe accident progression and phenomenological responses, in the validation and verification (V and V) of severe accident models or codes as they are developed. The U.S. nuclear utility industry has made substantial strides in the past 12 years in the accident prevention, mitigation and management arena. These strides are a product of the industry's preference for a logical and systematic approach to change. (orig.)

Robustness of inflation to inhomogeneous initial conditions

Energy Technology Data Exchange (ETDEWEB)

Clough, Katy; Lim, Eugene A. [Theoretical Particle Physics and Cosmology Group, Physics Department, Kings College London, Strand, London WC2R 2LS (United Kingdom); DiNunno, Brandon S.; Fischler, Willy; Flauger, Raphael; Paban, Sonia, E-mail: katy.clough@kcl.ac.uk, E-mail: eugene.a.lim@gmail.com, E-mail: bsd86@physics.utexas.edu, E-mail: fischler@physics.utexas.edu, E-mail: flauger@physics.utexas.edu, E-mail: paban@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, TX, 78712 (United States)

2017-09-01

We consider the effects of inhomogeneous initial conditions in both the scalar field profile and the extrinsic curvature on different inflationary models. In particular, we compare the robustness of small field inflation to that of large field inflation, using numerical simulations with Einstein gravity in 3+1 dimensions. We find that small field inflation can fail in the presence of subdominant gradient energies, suggesting that it is much less robust to inhomogeneities than large field inflation, which withstands dominant gradient energies. However, we also show that small field inflation can be successful even if some regions of spacetime start out in the region of the potential that does not support inflation. In the large field case, we confirm previous results that inflation is robust if the inflaton occupies the inflationary part of the potential. Furthermore, we show that increasing initial scalar gradients will not form sufficiently massive inflation-ending black holes if the initial hypersurface is approximately flat. Finally, we consider the large field case with a varying extrinsic curvature K , such that some regions are initially collapsing. We find that this may again lead to local black holes, but overall the spacetime remains inflationary if the spacetime is open, which confirms previous theoretical studies.

Initial Stage Reference Search : Driver Simulators to Test Shared Controls, Limited Autonomy Vehicle Systems

Science.gov (United States)

2015-09-01

This literature review and reference scanning focuses on the use of driver simulators for semiautonomous (or shared control) vehicle systems (2012present), including related research from other modes of transportation (e.g., rail or aviation). Foc...

The simulator Neck-Mfgs and its training status

International Nuclear Information System (INIS)

Setnikar, T.; Pribozic, F.; Srebotnjak, E.; Gortnar, O.; Kovacic, J.; Stritar, A.

1998-01-01

This paper presents the status and training possibilities on Krsko NPP Multi-Functional Simulator (NEK-MFS). Since spring 1997 it serves as a training facility in Nuclear Training Center. During first year of operation the simulator NEK-MFS was found to be a very useful Krsko NPP specific tool which is capable to support both the initial operator training program and licensed operator retraining activities.(author)

Simulation and New Learning Technologies.

Science.gov (United States)

Issenberg, S. Barry; Gordon, Michael S.; Gordon, David Lee; Safford, Robert E.; Hart, Ian R.

2001-01-01

In the future, virtual reality technology based initially on data from Visible Human Data sets will provide the majority of simulation-based training. Indicates that evidence-based outcomes must show these systems to be effective instruments for teaching and assessment, and medical educators must be willing to effect change in medical education to…

Neutronic/Thermalhydraulic Coupling Technigues for Sodium Cooled Fast Reactor Simulations

Energy Technology Data Exchange (ETDEWEB)

Jean Ragusa; Andrew Siegel; Jean-Michel Ruggieri

2010-09-28

The objective of this project was to test new coupling algorithms and enable efficient and scalable multi-physics simulations of advanced nuclear reactors, with considerations regarding the implementation of such algorithms in massively parallel environments. Numerical tests were carried out to verify the proposed approach and the examples included some reactor transients. The project was directly related to the Sodium Fast Reactor program element of the Generation IV Nuclear Energy Systems Initiative and the Advanced Fuel cycle Initiative, and, supported the requirement of high-fidelity simulation as a mean of achieving the goals of the presidential Global Nuclear Energy Partnership (GNEP) vision.

Comparison of a 3-D DEM simulation with MRI data

Science.gov (United States)

Ng, Tang-Tat; Wang, Changming

2001-04-01

This paper presents a comparison of a granular material studied experimentally and numerically. Simple shear tests were performed inside the magnetic core of magnetic resonance imaging (MRI) equipment. Spherical pharmaceutical pills were used as the granular material, with each pill's centre location determined by MRI. These centre locations in the initial assembly were then used as the initial configuration in the numerical simulation using the discrete element method. The contact properties between pharmaceutical pills used in the numerical simulation were obtained experimentally. The numerical predication was compared with experimental data at both macroscopic and microscopic levels. Good agreement was found at both levels.

MONTE CARLO SIMULATIONS OF GLOBULAR CLUSTER EVOLUTION. V. BINARY STELLAR EVOLUTION

International Nuclear Information System (INIS)

Chatterjee, Sourav; Umbreit, Stefan; Rasio, Frederic A.; Fregeau, John M.

2010-01-01

We study the dynamical evolution of globular clusters containing primordial binaries, including full single and binary stellar evolution using our Monte Carlo cluster evolution code updated with an adaptation of the single and binary stellar evolution codes SSE and BSE from Hurley et al. We describe the modifications that we have made to the code. We present several test calculations and comparisons with existing studies to illustrate the validity of the code. We show that our code finds very good agreement with direct N-body simulations including primordial binaries and stellar evolution. We find significant differences in the evolution of the global properties of the simulated clusters using stellar evolution compared with simulations without any stellar evolution. In particular, we find that the mass loss from the stellar evolution acts as a significant energy production channel simply by reducing the total gravitational binding energy and can significantly prolong the initial core contraction phase before reaching the binary-burning quasi-steady state of the cluster evolution. We simulate a large grid of models varying the initial cluster mass, binary fraction, and concentration parameter, and we compare properties of the simulated clusters with those of the observed Galactic globular clusters (GGCs). We find that simply including stellar evolution in our simulations and assuming the typical initial cluster half-mass radius is approximately a few pc independent of mass, our simulated cluster properties agree well with the observed GGC properties such as the core radius and the ratio of the core radius to the half-mass radius. We explore in some detail qualitatively different clusters in different phases of their evolution and construct synthetic Hertzsprung-Russell diagrams for these clusters.

Statistics of a mixed Eulerian-Lagrangian velocity increment in fully developed turbulence

International Nuclear Information System (INIS)

Friedrich, R; Kamps, O; Grauer, R; Homann, H

2009-01-01

We investigate the relationship between Eulerian and Lagrangian probability density functions obtained from numerical simulations of two-dimensional as well as three-dimensional turbulence. We show that in contrast to the structure functions of the Lagrangian velocity increment δ τ v(y)=u(x(y, τ), τ)- u(y, 0), where u(x, t) denotes the Eulerian velocity and x(y, t) the particle path initially starting at x(y, 0)=y, the structure functions of the velocity increment δ τ w(y)=u(x(y, τ), τ)- u(y, τ) exhibit a wide range of scaling behavior. Similar scaling indices are detected for the structure functions for particles diffusing in frozen turbulent fields. Furthermore, we discuss a connection to the scaling of Eulerian transversal structure functions.

Visual software system for memory interleaving simulation

Directory of Open Access Journals (Sweden)

Milenković Katarina

2017-01-01

Full Text Available This paper describes the visual software system for memory interleaving simulation (VSMIS, implemented for the purpose of the course Computer Architecture and Organization 1, at the School of Electrical Engineering, University of Belgrade. The simulator enables students to expand their knowledge through practical work in the laboratory, as well as through independent work at home. VSMIS gives users the possibility to initialize parts of the system and to control simulation steps. The user has the ability to monitor simulation through graphical representation. It is possible to navigate through the entire hierarchy of the system using simple navigation. During the simulation the user can observe and set the values of the memory location. At any time, the user can reset the simulation of the system and observe it for different memory states; in addition, it is possible to save the current state of the simulation and continue with the execution of the simulation later. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III44009

Intelligently interactive combat simulation

Science.gov (United States)

Fogel, Lawrence J.; Porto, Vincent W.; Alexander, Steven M.

2001-09-01

To be fully effective, combat simulation must include an intelligently interactive enemy... one that can be calibrated. But human operated combat simulations are uncalibratable, for we learn during the engagement, there's no average enemy, and we cannot replicate their culture/personality. Rule-based combat simulations (expert systems) are not interactive. They do not take advantage of unexpected mistakes, learn, innovate, and reflect the changing mission/situation. And it is presumed that the enemy does not have a copy of the rules, that the available experts are good enough, that they know why they did what they did, that their combat experience provides a sufficient sample and that we know how to combine the rules offered by differing experts. Indeed, expert systems become increasingly complex, costly to develop, and brittle. They have face validity but may be misleading. In contrast, intelligently interactive combat simulation is purpose- driven. Each player is given a well-defined mission, reference to the available weapons/platforms, their dynamics, and the sensed environment. Optimal tactics are discovered online and in real-time by simulating phenotypic evolution in fast time. The initial behaviors are generated randomly or include hints. The process then learns without instruction. The Valuated State Space Approach provides a convenient way to represent any purpose/mission. Evolutionary programming searches the domain of possible tactics in a highly efficient manner. Coupled together, these provide a basis for cruise missile mission planning, and for driving tank warfare simulation. This approach is now being explored to benefit Air Force simulations by a shell that can enhance the original simulation.

GLISSANDO: GLauber Initial-State Simulation AND mOre…

Science.gov (United States)

Broniowski, Wojciech; Rybczyński, Maciej; Bożek, Piotr

2009-01-01

We present a Monte Carlo generator for a variety of Glauber-like models (the wounded-nucleon model, binary collisions model, mixed model, model with hot spots). These models describe the early stages of relativistic heavy-ion collisions, in particular the spatial distribution of the transverse energy deposition which ultimately leads to production of particles from the interaction region. The original geometric distribution of sources in the transverse plane can be superimposed with a statistical distribution simulating the dispersion in the generated transverse energy in each individual collision. The program generates inter alia the fixed-axes (standard) and variable-axes (participant) two-dimensional profiles of the density of sources in the transverse plane and their azimuthal Fourier components. These profiles can be used in further analysis of physical phenomena, such as the jet quenching, event-by-event hydrodynamics, or analysis of the elliptic flow and its fluctuations. Characteristics of the event (multiplicities, eccentricities, Fourier coefficients, etc.) are stored in a ROOT file and can be analyzed off-line. In particular, event-by-event studies can be carried out in a simple way. A number of ROOT scripts is provided for that purpose. Supplied variants of the code can also be used for the proton-nucleus and deuteron-nucleus collisions. Program summaryProgram title: GLISSANDO Catalogue identifier: AEBS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4452 No. of bytes in distributed program, including test data, etc.: 34 766 Distribution format: tar.gz Programming language: C++ Computer: any computer with a C++ compiler and the ROOT environment [R. Brun, et al., Root Users Guide 5.16, CERN

Study of Z' {yields} e{sup +}e{sup -} in full simulation with regard to discrimination between models beyond the standard model

Energy Technology Data Exchange (ETDEWEB)

Schafer, M

2004-09-01

Although experimental results so far agree with predictions of the standard model, it is widely felt to be incomplete. Many prospective theories beyond the standard model predict extra neutral gauge bosons, denoted by Z', which might be light enough to be accessible at the LHC. Observables sensitive to the properties of these extra gauge bosons might be used to discriminate between the different theories beyond the standard model. In the present work several of these observables (total decay width, leptonic cross-section and forward-backward asymmetries) are studied at generation level and with a full simulation in the ATLAS detector. The Z' {yields} e{sup +}e{sup -} decay channel was chosen and 2 values for the mass of Z': 1.5 TeV and 4 TeV. Background is studied as well and it is confirmed that a Z' boson could easily be discovered at the chosen masses. It is shown that even in full simulation the studied observables can be determined with a good precision. In a next step a discrimination strategy has to be developed given the presented methods to extract the variables and their precision. (author)

Establishing precursor events for stress corrosion cracking initiation in type 304L stainless steel

International Nuclear Information System (INIS)

Khan, M.U.F.; Raja, V.S.; Roychowdhury, S.; Kain, V.

2015-01-01

The present study attempts to establish slip band emergence, due to localized deformation, as a precursor event for SCC initiation in type 304L SS. The unidirectional tensile loading was used for straining flat tensile specimen, less than 10% strain, in air, 0.5 M NaCl + 0.5 M H 2 SO 4 and boiling water reactor (BWR) simulated environment (288 C. degrees, 10 MPa). The surface features were characterized using optical microscopy, scanning electron microscopy (including electron backscattered diffraction-EBSD) and atomic force microscopy. The study shows that with increase in strain level, during unidirectional slow strain rate test (SSRT), average slip band height increases in air and the attack on slip lines occurs in acidified chloride environment. In BWR simulated environment, preferential oxidation on slip lines and initiation of a few cracks on some of the slip lines are observed. Based on the observation, the study suggests slip bands, formed due to localized deformation, to act as a precursor for SCC initiation. (authors)

Study on penetration-induced initiation of energetic fragment

Science.gov (United States)

Qiao, Xiangxin; Xu, Heyang

2017-09-01

In order to investigate penetration-induced initiation of energetic fragment penetrating target, PTFE/Al (mass ratio 73.5/26.5) pressed and sintered into a Ф8mm × 8mm cylinder. To form energetic fragment, the cylinder was put into a closed container made by 35CrMnSiA. The container is 12mm long, 2mm thick. Energetic fragments were launched by a 14.5mm ballistic gun with a series of velocities and the penetrate process was simulated by AUTODYN-3D. The results show that the stress peak of energetic material exceed the initiation threshold, and energetic material will deflagrate, when energetic fragments impact velocity more than 800 m/s. The research results can provide reference for designs of energetic warhead.

Research initiatives for plug-and-play scientific computing

International Nuclear Information System (INIS)

McInnes, Lois Curfman; Dahlgren, Tamara; Nieplocha, Jarek; Bernholdt, David; Allan, Ben; Armstrong, Rob; Chavarria, Daniel; Elwasif, Wael; Gorton, Ian; Kenny, Joe; Krishan, Manoj; Malony, Allen; Norris, Boyana; Ray, Jaideep; Shende, Sameer

2007-01-01

This paper introduces three component technology initiatives within the SciDAC Center for Technology for Advanced Scientific Component Software (TASCS) that address ever-increasing productivity challenges in creating, managing, and applying simulation software to scientific discovery. By leveraging the Common Component Architecture (CCA), a new component standard for high-performance scientific computing, these initiatives tackle difficulties at different but related levels in the development of component-based scientific software: (1) deploying applications on massively parallel and heterogeneous architectures, (2) investigating new approaches to the runtime enforcement of behavioral semantics, and (3) developing tools to facilitate dynamic composition, substitution, and reconfiguration of component implementations and parameters, so that application scientists can explore tradeoffs among factors such as accuracy, reliability, and performance

Large Eddy Simulations of a Bottom Boundary Layer Under a Shallow Geostrophic Front

Science.gov (United States)

Bateman, S. P.; Simeonov, J.; Calantoni, J.

2017-12-01

The unstratified surf zone and the stratified shelf waters are often separated by dynamic fronts that can strongly impact the character of the Ekman bottom boundary layer. Here, we use large eddy simulations to study the turbulent bottom boundary layer associated with a geostrophic current on a stratified shelf of uniform depth. The simulations are initialized with a spatially uniform vertical shear that is in geostrophic balance with a pressure gradient due to a linear horizontal temperature variation. Superposed on the temperature front is a stable vertical temperature gradient. As turbulence develops near the bottom, the turbulence-induced mixing gradually erodes the initial uniform temperature stratification and a well-mixed layer grows in height until the turbulence becomes fully developed. The simulations provide the spatial distribution of the turbulent dissipation and the Reynolds stresses in the fully developed boundary layer. We vary the initial linear stratification and investigate its effect on the height of the bottom boundary layer and the turbulence statistics. The results are compared to previous models and simulations of stratified bottom Ekman layers.

Simulating human behavior for national security human interactions.

Energy Technology Data Exchange (ETDEWEB)

Bernard, Michael Lewis; Hart, Dereck H.; Verzi, Stephen J.; Glickman, Matthew R.; Wolfenbarger, Paul R.; Xavier, Patrick Gordon

2007-01-01

This 3-year research and development effort focused on what we believe is a significant technical gap in existing modeling and simulation capabilities: the representation of plausible human cognition and behaviors within a dynamic, simulated environment. Specifically, the intent of the ''Simulating Human Behavior for National Security Human Interactions'' project was to demonstrate initial simulated human modeling capability that realistically represents intra- and inter-group interaction behaviors between simulated humans and human-controlled avatars as they respond to their environment. Significant process was made towards simulating human behaviors through the development of a framework that produces realistic characteristics and movement. The simulated humans were created from models designed to be psychologically plausible by being based on robust psychological research and theory. Progress was also made towards enhancing Sandia National Laboratories existing cognitive models to support culturally plausible behaviors that are important in representing group interactions. These models were implemented in the modular, interoperable, and commercially supported Umbra{reg_sign} simulation framework.

Off-line programming and simulation in handling nuclear components

International Nuclear Information System (INIS)

Baker, C.P.

1993-10-01

IGRIP was used to create a simulation of the robotic workcell design for handling components at the PANTEX nuclear arms facility. This initial simulation identified problems with the customer's proposed worker layout, and allowed a correction to be proposed. Refinement of the IGRIP simulation allowed the design and construction of a workcell mock-up and accurate off-line programming of the system. IGRIP's off-line programming capabilities are being used to develop the motion control code for the workcell. PNLs success in this area suggests that simulation and off-line programming may be valuable tools for developing robotics in some automation resistant industries

Ozone-initiated chemistry in an occupied simulated aircraft cabin.

Science.gov (United States)

Weschler, Charles J; Wisthaler, Armin; Cowlin, Shannon; Tamás, Gyöngyi; Strøm-Tejsen, Peter; Hodgson, Alfred T; Destaillats, Hugo; Herrington, Jason; Zhang, Junfeng; Nazaroff, William W

2007-09-01

We have used multiple analytical methods to characterize the gas-phase products formed when ozone was added to cabin air during simulated 4-hour flights that were conducted in a reconstructed section of a B-767 aircraft containing human occupants. Two separate groups of 16 females were each exposed to four conditions: low air exchange (4.4 (h-1)), exchange, 61-64 ppb ozone; high air exchange (8.8 h(-1)), exchange, 73-77 ppb ozone. The addition of ozone to the cabin air increased the levels of identified byproducts from approximately 70 to 130 ppb at the lower air exchange rate and from approximately 30 to 70 ppb at the higher air exchange rate. Most of the increase was attributable to acetone, nonanal, decanal, 4-oxopentanal (4-OPA), 6-methyl-5-hepten-2-one (6-MHO), formic acid, and acetic acid, with 0.25-0.30 mol of quantified product volatilized per mol of ozone consumed. Several of these compounds reached levels above their reported odor thresholds. Most byproducts were derived from surface reactions with occupants and their clothing, consistent with the inference that occupants were responsible for the removal of >55% of the ozone in the cabin. The observations made in this study have implications for other indoor settings. Whenever human beings and ozone are simultaneously present, one anticipates production of acetone, nonanal, decanal, 6-MHO, geranyl acetone, and 4-OPA.

Study of crack initiation in low-cycle fatigue of an austenitic stainless steel

International Nuclear Information System (INIS)

Mu, P.

2011-03-01

The material studied is an austenitic stainless steel, that is widely used in nuclear equipment for its very high corrosion resistance combined to good mechanical properties. Although crack initiation is proved to play an important role in fatigue, its mechanisms have not been fully understood. Some crack initiation criteria based on physical mechanisms of plastic deformation have been defined. However, these criteria are not easy to use and valid, as they need local variables at the grain scale. The present study aims at establishing a crack initiation criterion in low-cycle fatigue, which should be usable under variable amplitude loading conditions. Tension-compression fatigue tests were first carried out to characterize the mechanical behavior of the stainless steel AISI 316L. The mechanical behavior was simulated using a self-consistent model using a crystalline plastic law based on dislocation densities. The evolution of surface damage was observed during a fatigue test using an in situ optical microscopic device. Cracks were analyzed after 2000 cycles and their crystallographic characteristics calculated. As surface grains exhibit larger strain because they are less constraint by neighbor grains, a specific numerical frame is necessary to determine stress state in surface grains. A localization law specific to surface grains under cyclic loading was identified from finite element simulations. The proposed form needs an intergranular accommodation variable, on the pattern of the localization law of Cailletaud-Pilvin. Stress-strain state in surface grains was simulated. Potential indicators for crack initiation were then compared on a same experimental data base. Indicators based on the equivalent plastic strain were found to be suitable indicators of fatigue damage. (author)

The dependence of stellar properties on initial cloud density

Science.gov (United States)

Jones, Michael O.; Bate, Matthew R.

2018-05-01

We investigate the dependence of stellar properties on the initial mean density of the molecular cloud in which stellar clusters form using radiation hydrodynamical simulations that resolve the opacity limit for fragmentation. We have simulated the formation of three star clusters from the gravitational collapse of molecular clouds whose densities vary by a factor of a hundred. As with previous calculations including radiative feedback, we find that the dependence of the characteristic stellar mass, Mc, on the initial mean density of the cloud, ρ, is weaker than the dependence of the thermal Jeans mass. However, unlike previous calculations, which found no statistically significant variation in the median mass with density, we find a weak dependence approximately of the form Mc∝ρ-1/5. The distributions of properties of multiple systems do not vary significantly between the calculations. We compare our results to the result of observational surveys of star-forming regions, and suggest that the similarities between the properties of our lowest density calculation and the nearby Taurus-Auriga region indicate that the apparent excess of solar-type stars observed may be due to the region's low density.

The Actuator Surface Model: A New Navier-Stokes Based Model for Rotor Computations

DEFF Research Database (Denmark)

Shen, Wen Zhong; Zhang, J.H.; Sørensen, Jens Nørkær

2009-01-01

This paper presents a new numerical technique for simulating two-dimensional wind turbine flow. The method, denoted as the 2D actuator surface technique, consists of a two-dimensional Navier-Stokes solver in which the pressure distribution is represented by body forces that are distributed along ....... In the last part, the actuator surface technique is applied to compute the flow past a two-bladed vertical axis wind turbine equipped with NACA 0012 airfoils. Comparisons with experimental data show an encouraging performance of the method.......This paper presents a new numerical technique for simulating two-dimensional wind turbine flow. The method, denoted as the 2D actuator surface technique, consists of a two-dimensional Navier-Stokes solver in which the pressure distribution is represented by body forces that are distributed along...

Integrating Symbolic Execution with Sensornet Simulation for Efficient Bug Finding

OpenAIRE

Österlind, Fredrik; Sasnauskas, Raimondas; Dustmann, Oscar Soria; Dunkels, Adam; Wehrle, Klaus

2010-01-01

High-coverage testing of sensornet applications is vital for pre-deployment bug cleansing, but has previously been difficult due to the limited set of available tools. We integrate the KleeNet symbolic execution engine with the COOJA network simulator to allow for straight-forward and intuitive high-coverage testing initiated from a simulation environment. A tight coupling of simulation and testing helps detect, narrow down, and fix complex interaction bugs in an early ...

Remapping simulated halo catalogues in redshift space

OpenAIRE

Mead, Alexander; Peacock, John

2014-01-01

We discuss the extension to redshift space of a rescaling algorithm, designed to alter the effective cosmology of a pre-existing simulated particle distribution or catalogue of dark matter haloes. The rescaling approach was initially developed by Angulo & White and was adapted and applied to halo catalogues in real space in our previous work. This algorithm requires no information other than the initial and target cosmological parameters, and it contains no tuned parameters. It is shown here ...

Validation of Robotic Surgery Simulator (RoSS).

Science.gov (United States)

Kesavadas, Thenkurussi; Stegemann, Andrew; Sathyaseelan, Gughan; Chowriappa, Ashirwad; Srimathveeravalli, Govindarajan; Seixas-Mikelus, Stéfanie; Chandrasekhar, Rameella; Wilding, Gregory; Guru, Khurshid

2011-01-01

Recent growth of daVinci Robotic Surgical System as a minimally invasive surgery tool has led to a call for better training of future surgeons. In this paper, a new virtual reality simulator, called RoSS is presented. Initial results from two studies - face and content validity, are very encouraging. 90% of the cohort of expert robotic surgeons felt that the simulator was excellent or somewhat close to the touch and feel of the daVinci console. Content validity of the simulator received 90% approval in some cases. These studies demonstrate that RoSS has the potential of becoming an important training tool for the daVinci surgical robot.

New method for initial density reconstruction

Science.gov (United States)

Shi, Yanlong; Cautun, Marius; Li, Baojiu

2018-01-01

A theoretically interesting and practically important question in cosmology is the reconstruction of the initial density distribution provided a late-time density field. This is a long-standing question with a revived interest recently, especially in the context of optimally extracting the baryonic acoustic oscillation (BAO) signals from observed galaxy distributions. We present a new efficient method to carry out this reconstruction, which is based on numerical solutions to the nonlinear partial differential equation that governs the mapping between the initial Lagrangian and final Eulerian coordinates of particles in evolved density fields. This is motivated by numerical simulations of the quartic Galileon gravity model, which has similar equations that can be solved effectively by multigrid Gauss-Seidel relaxation. The method is based on mass conservation, and does not assume any specific cosmological model. Our test shows that it has a performance comparable to that of state-of-the-art algorithms that were very recently put forward in the literature, with the reconstructed density field over ˜80 % (50%) correlated with the initial condition at k ≲0.6 h /Mpc (1.0 h /Mpc ). With an example, we demonstrate that this method can significantly improve the accuracy of BAO reconstruction.

Non-dissipative kinetic simulation and analytical solution of three-mode equations of ion temperature gradient instability

International Nuclear Information System (INIS)

Watanabe, T.-H.; Sugama, H.; Sato, T.

1999-12-01

A non-dissipative drift kinetic simulation scheme, which rigorously satisfies the time-reversibility, is applied to the three-mode coupling problem of the ion temperature gradient (ITG) instability. It is found from the simulation that the three-mode ITG system repeats growth and decay with a period which shows a logarithmic divergence for infinitesimal initial perturbations. Accordingly, time average of the mode amplitude vanishes, as the initial amplitude approaches to zero. An exact solution is analytically given for a class of initial conditions. An excellent agreement is confirmed between the analytical solution and numerical results. The results obtained here provide a useful reference for basic benchmarking of theories and simulation of the ITG modes. (author)

Simulations of Hall reconnection in partially ionized plasmas

Science.gov (United States)

Innocenti, Maria Elena; Jiang, Wei; Lapenta, Giovanni

2017-04-01

Magnetic reconnection occurs in the Hall, partially ionized regime in environments as diverse as molecular clouds, protostellar disks and regions of the solar chromosphere. While much is known about Hall reconnection in fully ionized plasmas, Hall reconnection in partially ionized plasmas is, in comparison, still relatively unexplored. This notwithstanding the fact that partial ionization is expected to affect fundamental processes in reconnection such as the transition from the slow, fluid to the fast, kinetic regime, the value of the reconnection rate and the dimensions of the diffusion regions [Malyshkin and Zweibel 2011 , Zweibel et al. 2011]. We present here the first, to our knowledge, fully kinetic simulations of Hall reconnection in partially ionized plasmas. The interaction of electrons and ions with the neutral background is realistically modelled via a Monte Carlo plug-in coded into the semi-implicit, fully kinetic code iPic3D [Markidis 2010]. We simulate a plasma with parameters compatible with the MRX experiments illustrated in Zweibel et al. 2011 and Lawrence et al. 2013, to be able to compare our simulation results with actual experiments. The gas and ion temperature is T=3 eV, the ion to electron temperature ratio is Tr=0.44, ion and electron thermal velocities are calculated accordingly resorting to a reduced mass ratio and a reduced value of the speed of light to reduce the computational costs of the simulations. The initial density of the plasma is set at n= 1.1 1014 cm-3 and is then left free to change during the simulation as a result of gas-plasma interaction. A set of simulations with initial ionisation percentage IP= 0.01, 0.1, 0.2, 0.6 is presented and compared with a reference simulation where no background gas is present (full ionization). In this first set of simulations, we assume to be able to externally control the initial relative densities of gas and plasma. Within this parameter range, the ion but not the electron population is

Stress analysis and deformation prediction of sheet metal workpieces based on finite element simulation

OpenAIRE

Ren Penghao; Wang Aimin; Wang Xiaolong; Zhang Yanlin

2017-01-01

After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation ...

Resolution convergence in cosmological hydrodynamical simulations using adaptive mesh refinement

Science.gov (United States)

Snaith, Owain N.; Park, Changbom; Kim, Juhan; Rosdahl, Joakim

2018-06-01

We have explored the evolution of gas distributions from cosmological simulations carried out using the RAMSES adaptive mesh refinement (AMR) code, to explore the effects of resolution on cosmological hydrodynamical simulations. It is vital to understand the effect of both the resolution of initial conditions (ICs) and the final resolution of the simulation. Lower initial resolution simulations tend to produce smaller numbers of low-mass structures. This will strongly affect the assembly history of objects, and has the same effect of simulating different cosmologies. The resolution of ICs is an important factor in simulations, even with a fixed maximum spatial resolution. The power spectrum of gas in simulations using AMR diverges strongly from the fixed grid approach - with more power on small scales in the AMR simulations - even at fixed physical resolution and also produces offsets in the star formation at specific epochs. This is because before certain times the upper grid levels are held back to maintain approximately fixed physical resolution, and to mimic the natural evolution of dark matter only simulations. Although the impact of hold-back falls with increasing spatial and IC resolutions, the offsets in the star formation remain down to a spatial resolution of 1 kpc. These offsets are of the order of 10-20 per cent, which is below the uncertainty in the implemented physics but are expected to affect the detailed properties of galaxies. We have implemented a new grid-hold-back approach to minimize the impact of hold-back on the star formation rate.

Magnetic field is the dominant factor to induce the response of Streptomyces avermitilis in altered gravity simulated by diamagnetic levitation.

Directory of Open Access Journals (Sweden)

Mei Liu

Full Text Available BACKGROUND: Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to simulate an altered gravity environment, as in space. In this study, using Streptomyces avermitilis as the test organism, we investigate whether changes in magnetic field and altered gravity induce changes in morphology and secondary metabolism. We find that a strong magnetic field (12T inhibit the morphological development of S. avermitilis in solid culture, and increase the production of secondary metabolites. METHODOLOGY/PRINCIPAL FINDINGS: S. avermitilis on solid medium was levitated at 0 g*, 1 g* and 2 g* in an altered gravity environment simulated by diamagnetic levitation and under a strong magnetic field, denoted by the asterix. The morphology was obtained by electromicroscopy. The production of the secondary metabolite, avermectin, was determined by OD(245 nm. The results showed that diamagnetic levitation could induce a physiological response in S. avermitilis. The difference between 1 g* and the control group grown without the strong magnetic field (1 g, showed that the magnetic field was a more dominant factor influencing changes in morphology and secondary metabolite production, than altered gravity. CONCLUSION/SIGNIFICANCE: We have discovered that magnetic field, rather than altered gravity, is the dominant factor in altered gravity simulated by diamagnetic levitation, therefore care should to be taken in the interpretation of results when using diamagnetic levitation as a technique to simulate altered gravity. Hence, these results are significant, and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.

Effect of dissolved hydrogen concentration on IASCC initiation susceptibility of type 316 stainless steels

Energy Technology Data Exchange (ETDEWEB)

Choi, Min-Jae; Kim, Sung Woo; Hwang, Seong Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

The effect of DH concentration on PWSCC of nickel based alloys has been studied, higher dissolved hydrogen strategy is being considered to obtain partial mitigation of PWSCC. In the case of stainless steels, it is necessary to research the effect of DH concentration on irradiation assisted stress corrosion cracking(IASCC). In this research, we tried to evaluate the effect of DH concentration on IASCC initiation susceptibility using the proton irradiated type 316 stainless steels under the condition of simulated primary water. The slow strain rate tests were performed using the proton irradiated type 316 stainless steels at the simulated primary water conditions, crack length per unit area for all tested specimens were calculated. IASCC initiation susceptibility was increased by increasing irradiation doses and by increasing DH concentration.

Self-Consistent Model of Magnetospheric Electric Field, Ring Current, Plasmasphere, and Electromagnetic Ion Cyclotron Waves: Initial Results

Science.gov (United States)

Gamayunov, K. V.; Khazanov, G. V.; Liemohn, M. W.; Fok, M.-C.; Ridley, A. J.

2009-01-01

Further development of our self-consistent model of interacting ring current (RC) ions and electromagnetic ion cyclotron (EMIC) waves is presented. This model incorporates large scale magnetosphere-ionosphere coupling and treats self-consistently not only EMIC waves and RC ions, but also the magnetospheric electric field, RC, and plasmasphere. Initial simulations indicate that the region beyond geostationary orbit should be included in the simulation of the magnetosphere-ionosphere coupling. Additionally, a self-consistent description, based on first principles, of the ionospheric conductance is required. These initial simulations further show that in order to model the EMIC wave distribution and wave spectral properties accurately, the plasmasphere should also be simulated self-consistently, since its fine structure requires as much care as that of the RC. Finally, an effect of the finite time needed to reestablish a new potential pattern throughout the ionosphere and to communicate between the ionosphere and the equatorial magnetosphere cannot be ignored.

Evolution of the Orszag-Tang vortex system in a compressible medium. I - Initial average subsonic flow

Science.gov (United States)

Dahlburg, R. B.; Picone, J. M.

1989-01-01

The results of fully compressible, Fourier collocation, numerical simulations of the Orszag-Tang vortex system are presented. The initial conditions for this system consist of a nonrandom, periodic field in which the magnetic and velocity field contain X points but differ in modal structure along one spatial direction. The velocity field is initially solenoidal, with the total initial pressure field consisting of the superposition of the appropriate incompressible pressure distribution upon a flat pressure field corresponding to the initial, average Mach number of the flow. In these numerical simulations, this initial Mach number is varied from 0.2-0.6. These values correspond to average plasma beta values ranging from 30.0 to 3.3, respectively. It is found that compressible effects develop within one or two Alfven transit times, as manifested in the spectra of compressible quantities such as the mass density and the nonsolenoidal flow field. These effects include (1) a retardation of growth of correlation between the magnetic field and the velocity field, (2) the emergence of compressible small-scale structure such as massive jets, and (3) bifurcation of eddies in the compressible flow field. Differences between the incompressible and compressible results tend to increase with increasing initial average Mach number.

Nonlinear energy transfer and current sheet development in localized Alfvén wavepacket collisions in the strong turbulence limit

Science.gov (United States)

Verniero, J. L.; Howes, G. G.; Klein, K. G.

2018-02-01

In space and astrophysical plasmas, turbulence is responsible for transferring energy from large scales driven by violent events or instabilities, to smaller scales where turbulent energy is ultimately converted into plasma heat by dissipative mechanisms. The nonlinear interaction between counterpropagating Alfvén waves, denoted Alfvén wave collisions, drives this turbulent energy cascade, as recognized by early work with incompressible magnetohydrodynamic (MHD) equations. Recent work employing analytical calculations and nonlinear gyrokinetic simulations of Alfvén wave collisions in an idealized periodic initial state have demonstrated the key properties that strong Alfvén wave collisions mediate effectively the transfer of energy to smaller perpendicular scales and self-consistently generate current sheets. For the more realistic case of the collision between two initially separated Alfvén wavepackets, we use a nonlinear gyrokinetic simulation to show here that these key properties persist: strong Alfvén wavepacket collisions indeed facilitate the perpendicular cascade of energy and give rise to current sheets. Furthermore, the evolution shows that nonlinear interactions occur only while the wavepackets overlap, followed by a clean separation of the wavepackets with straight uniform magnetic fields and the cessation of nonlinear evolution in between collisions, even in the gyrokinetic simulation presented here which resolves dispersive and kinetic effects beyond the reach of the MHD theory.

Study of Z' {yields} e{sup +}e{sup -} in full simulation with regard to discrimination between models beyond the standard model

Energy Technology Data Exchange (ETDEWEB)

Schafer, M

2004-09-01

Although experimental results so far agree with predictions of the standard model, it is widely felt to be incomplete. Many prospective theories beyond the standard model predict extra neutral gauge bosons, denoted by Z', which might be light enough to be accessible at the LHC. Observables sensitive to the properties of these extra gauge bosons might be used to discriminate between the different theories beyond the standard model. In the present work several of these observables (total decay width, leptonic cross-section and forward-backward asymmetries) are studied at generation level and with a full simulation in the ATLAS detector. The Z' {yields} e{sup +}e{sup -} decay channel was chosen and 2 values for the mass of Z': 1.5 TeV and 4 TeV. Background is studied as well and it is confirmed that a Z' boson could easily be discovered at the chosen masses. It is shown that even in full simulation the studied observables can be determined with a good precision. In a next step a discrimination strategy has to be developed given the presented methods to extract the variables and their precision. (author)

Effects of sub-domain structure on initial magnetization curve and domain size distribution of stacked media

International Nuclear Information System (INIS)

Sato, S.; Kumagai, S.; Sugita, R.

2015-01-01

In this paper, in order to confirm the sub-domain structure in stacked media demagnetized with in-plane field, initial magnetization curves and magnetic domain size distribution were investigated. Both experimental and simulation results showed that an initial magnetization curve for the medium demagnetized with in-plane field (MDI) initially rose faster than that for the medium demagnetized with perpendicular field (MDP). It is inferred that this is because the MDI has a larger number of domain walls than the MDP due to the existence of the sub-domains, resulting in an increase in the probability of domain wall motion. Dispersion of domain size for the MDI was larger than that for the MDP. This is because sub-domains are formed not only inside the domain but also at the domain boundary region, and they change the position of the domain boundary to affect the domain size. - Highlights: • An initial magnetization curve for MDI initially rose faster than that for MDP. • Dispersion of domain size for the MDI was larger than that for the MDP. • Experimental and simulation results can be explained by existence of sub-domains

experimental investigation of flow pattern around repelling

African Journals Online (AJOL)

A. Mahdieh NajafAbadi and M. M. Bateni

2017-09-01

Sep 1, 2017 ... FLOW-3D® software used to simulate flow pattern. The simulation was .... separated into separation zone, shear layer, vortices zone, end point of vorticity zone and primary flow zone. In the figure, b1 and b2 denote ... closer to the wall for the attractive spur dike. For case of the repelling spur dike, transverse.

2-d Simulations of Test Methods

DEFF Research Database (Denmark)

Thrane, Lars Nyholm

2004-01-01

One of the main obstacles for the further development of self-compacting concrete is to relate the fresh concrete properties to the form filling ability. Therefore, simulation of the form filling ability will provide a powerful tool in obtaining this goal. In this paper, a continuum mechanical...... approach is presented by showing initial results from 2-d simulations of the empirical test methods slump flow and L-box. This method assumes a homogeneous material, which is expected to correspond to particle suspensions e.g. concrete, when it remains stable. The simulations have been carried out when...... using both a Newton and Bingham model for characterisation of the rheological properties of the concrete. From the results, it is expected that both the slump flow and L-box can be simulated quite accurately when the model is extended to 3-d and the concrete is characterised according to the Bingham...

Simulation of spontaneous and variable global dust storms with the GFDL Mars GCM

OpenAIRE

Basu, Shabari; Wilson, John; Richardson, Mark; Ingersoll, Andrew

2006-01-01

We report on the successful simulation of global dust storms in a general circulation model. The simulated storms develop spontaneously in multiyear simulations and exhibit significant interannual variability. The simulated storms produce dramatic increases in atmospheric dustiness, global-mean air temperatures, and atmospheric circulation intensity, in accord with observations. As with observed global storms, spontaneous initiation of storms in the model occurs in southern spring and summer,...

MUSIC: MUlti-Scale Initial Conditions

Science.gov (United States)

Hahn, Oliver; Abel, Tom

2013-11-01

MUSIC generates multi-scale initial conditions with multiple levels of refinements for cosmological ‘zoom-in’ simulations. The code uses an adaptive convolution of Gaussian white noise with a real-space transfer function kernel together with an adaptive multi-grid Poisson solver to generate displacements and velocities following first- (1LPT) or second-order Lagrangian perturbation theory (2LPT). MUSIC achieves rms relative errors of the order of 10-4 for displacements and velocities in the refinement region and thus improves in terms of errors by about two orders of magnitude over previous approaches. In addition, errors are localized at coarse-fine boundaries and do not suffer from Fourier space-induced interference ringing.

Crack initiation and growth in welded structures

International Nuclear Information System (INIS)

Assire, A.

2000-01-01

. Concerning local approach, intergranular creep damage model of the Ecole des Mines de Paris is used for crack initiation and growth under creep and creep fatigue loading. Crack propagations are simulated with an adaptive re-meshing technique and are compared with experimental results for crack located in weld and base metal. A sensibility analysis shows that crack propagation strongly depend on the characteristic distance, which is needed to simulate crack growth with local approach, for the weld metal parameters. (author)

Stress analysis and deformation prediction of sheet metal workpieces based on finite element simulation

Directory of Open Access Journals (Sweden)

Ren Penghao

2017-01-01

Full Text Available After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation of the workpiece, a linear relationship between initial stress and deformation is found; Through simulative analysis of coupling direction-stress release, the superposing relationship between the deformation caused by coupling direction-stress and the deformation caused by single direction stress is found. The research results provide important theoretical support for the stress threshold setting and deformation controlling of the workpieces in the production practice.

THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATIONS OF BUOYANT BUBBLES IN GALAXY CLUSTERS

International Nuclear Information System (INIS)

O'Neill, S. M.; De Young, D. S.; Jones, T. W.

2009-01-01

We report results of three-dimensional magnetohydrodynamic simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three-dimensional extensions of two-dimensional calculations reported by Jones and De Young. Initially, spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into 'smoke rings', if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with β = P gas /P mag ∼ 3 can influence the dynamics of the bubbles, provided the fields are not tangled on scales comparable to or smaller than the size of the bubbles. Quasi-uniform, horizontal fields with initial β ∼ 10 2 bifurcated our bubbles before they rose more than about a scale height of the ICM, and substantially weaker fields produced clear distortions. These behaviors resulted from stretching and amplification of ICM fields trapped in irregularities along the top surface of the young bubbles. On the other hand, tangled magnetic fields with similar, modest strengths are generally less easily amplified by the bubble motions and are thus less influential in bubble evolution. Inclusion of a comparably strong, tangled magnetic field inside the initial bubbles had little effect on our bubble evolution, since those fields were quickly diminished through expansion of the bubble and reconnection of the initial field.

Spectrally accurate initial data in numerical relativity

Science.gov (United States)

Battista, Nicholas A.

Einstein's theory of general relativity has radically altered the way in which we perceive the universe. His breakthrough was to realize that the fabric of space is deformable in the presence of mass, and that space and time are linked into a continuum. Much evidence has been gathered in support of general relativity over the decades. Some of the indirect evidence for GR includes the phenomenon of gravitational lensing, the anomalous perihelion of mercury, and the gravitational redshift. One of the most striking predictions of GR, that has not yet been confirmed, is the existence of gravitational waves. The primary source of gravitational waves in the universe is thought to be produced during the merger of binary black hole systems, or by binary neutron stars. The starting point for computer simulations of black hole mergers requires highly accurate initial data for the space-time metric and for the curvature. The equations describing the initial space-time around the black hole(s) are non-linear, elliptic partial differential equations (PDE). We will discuss how to use a pseudo-spectral (collocation) method to calculate the initial puncture data corresponding to single black hole and binary black hole systems.

Neutronic/Thermal-hydraulic Coupling Technigues for Sodium Cooled Fast Reactor Simulations

International Nuclear Information System (INIS)

Ragusa, Jean; Siegel, Andrew; Ruggieri, Jean-Michel

2010-01-01

The objective of this project was to test new coupling algorithms and enable efficient and scalable multi-physics simulations of advanced nuclear reactors, with considerations regarding the implementation of such algorithms in massively parallel environments. Numerical tests were carried out to verify the proposed approach and the examples included some reactor transients. The project was directly related to the Sodium Fast Reactor program element of the Generation IV Nuclear Energy Systems Initiative and the Advanced Fuel cycle Initiative, and, supported the requirement of high-fidelity simulation as a mean of achieving the goals of the presidential Global Nuclear Energy Partnership (GNEP) vision.

PRODUCTION SYSTEM MODELING AND SIMULATION USING DEVS FORMALISM

OpenAIRE

Amaya Hurtado, Darío; Castillo Estepa, Ricardo Andrés; Avilés Montaño, Óscar Fernando; Ramos Sandoval, Olga Lucía

2014-01-01

This article presents the Discrete Event System Specification (DEVS) formalism, in their atomic and coupled configurations; it is used for discrete event systems modeling and simulation. Initially this work describes the analysis of discrete event systems concepts and its applicability. Then a comprehensive description of the DEVS formalism structure is presented, in order to model and simulate an industrial process, taking into account changes in parameters such as process service time, each...

The Fermi-Pasta-Ulam problem: Simulation and modern dynamics

International Nuclear Information System (INIS)

Weissert, T.P.

1992-01-01

In 1952, Enrico Fermi, John Pasta and Stanislaw Ulam (FPU) simulated the loaded string model, perturbed with small, nonlinear interaction terms. Because Poincare's theorem guarantees the non-existence of a complete set of integrals for three-body problem, they expected to see the diffusion of energy from its single-mode initial condition to all other modes of the string. But for every combination of initial conditions, the energy remained bounded within the lowest few modes. No theoretical explanation existed for this failure of the underlying hypothesis that erogidicity follows from the lack of a complete set of integrals of the motion in a Hamiltonian model. The author traces the history of this problem from the FPU simulation to the point that a consensus was reached concerning its solution twenty years later. During this period, the simulation of nonlinearly-perturbed integral models became the methodology for a new era in dynamics. Through the use of simulation, dynamicists discovered deterministic chaos, in which the exponential separation of pair orbits generate randomness in deterministic macroscopic systems, and a new kind of structure-related to the KAM theorem-that provides limited order in the absence of analytic integrals of the motions. The author maps the set of conceptually-related journal articles into a chronological inference topology that tracks the understanding of this problem of dynamics. Simulating non-integrable models on a digital computer requires the discretization of time and space. These approximations affect what the simulation can reveal about the model, and the model about reality. Simulations play the role of experiments on mathematical models. A discussion is presented of the issues that emerge with the use of simulation as a heuristic device and the groundwork is laid for an epistemology of simulation

Factors influencing initial cup stability in total hip arthroplasty.

Science.gov (United States)

Amirouche, Farid; Solitro, Giovanni; Broviak, Stefanie; Gonzalez, Mark; Goldstein, Wayne; Barmada, Riad

2014-12-01

One of the main goals in total hip replacement is to preserve the integrity of the hip kinematics, by well positioning the cup and to make sure its initial stability is congruent and attained. Achieving the latter is not trivial. A finite element model of the cup-bone interface simulating a realistic insertion and analysis of different scenarios of cup penetration, insertion, under-reaming and loading is investigated to determine certain measurable factors sensitivity to stress-strain outcome. The insertion force during hammering and its relation to the cup penetration during implantation is also investigated with the goal of determining the initial stability of the acetabular cup during total hip arthroplasty. The mathematical model was run in various configurations to simulate 1 and 2mm of under-reaming at various imposed insertion distances to mimic hammering and insertion of cup insertion into the pelvis. Surface contact and micromotion at the cup-bone interface were evaluated after simulated cup insertion and post-operative loading conditions. The results suggest a direct correlation between under-reaming and insertion force used to insert the acetabular cup on the micromotion and fixation at the cup-bone interface. While increased under-reaming and insertion force result in an increase amount of stability at the interface, approximately the same percentage of surface contact and micromotion reduction can be achieved with less insertion force. We need to exercise caution to determine the optimal configuration which achieves a good conformity without approaching the yield strength for bone. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modelling vacuum arcs : from plasma initiation to surface interactions

International Nuclear Information System (INIS)

Timko, H.

2011-01-01

A better understanding of vacuum arcs is desirable in many of today's 'big science' projects including linear colliders, fusion devices, and satellite systems. For the Compact Linear Collider (CLIC) design, radio-frequency (RF) breakdowns occurring in accelerating cavities influence efficiency optimisation and cost reduction issues. Studying vacuum arcs both theoretically as well as experimentally under well-defined and reproducible direct-current (DC) conditions is the first step towards exploring RF breakdowns. In this thesis, we have studied Cu DC vacuum arcs with a combination of experiments, a particle-in-cell (PIC) model of the arc plasma, and molecular dynamics (MD) simulations of the subsequent surface damaging mechanism. We have also developed the 2D Arc-PIC code and the physics model incorporated in it, especially for the purpose of modelling the plasma initiation in vacuum arcs. Assuming the presence of a field emitter at the cathode initially, we have identified the conditions for plasma formation and have studied the transitions from field emission stage to a fully developed arc. The 'footing' of the plasma is the cathode spot that supplies the arc continuously with particles; the high-density core of the plasma is located above this cathode spot. Our results have shown that once an arc plasma is initiated, and as long as energy is available, the arc is self-maintaining due to the plasma sheath that ensures enhanced field emission and sputtering.The plasma model can already give an estimate on how the time-to-breakdown changes with the neutral evaporation rate, which is yet to be determined by atomistic simulations. Due to the non-linearity of the problem, we have also performed a code-to-code comparison. The reproducibility of plasma behaviour and time-to-breakdown with independent codes increased confidence in the results presented here. Our MD simulations identified high-flux, high-energy ion bombardment as a possible mechanism forming the early

Species Entropies in the Kinetic Range of Collisionless Plasma Turbulence: Particle-in-cell Simulations

Science.gov (United States)

Gary, S. Peter; Zhao, Yinjian; Hughes, R. Scott; Wang, Joseph; Parashar, Tulasi N.

2018-06-01

Three-dimensional particle-in-cell simulations of the forward cascade of decaying turbulence in the relatively short-wavelength kinetic range have been carried out as initial-value problems on collisionless, homogeneous, magnetized electron-ion plasma models. The simulations have addressed both whistler turbulence at β i = β e = 0.25 and kinetic Alfvén turbulence at β i = β e = 0.50, computing the species energy dissipation rates as well as the increase of the Boltzmann entropies for both ions and electrons as functions of the initial dimensionless fluctuating magnetic field energy density ε o in the range 0 ≤ ε o ≤ 0.50. This study shows that electron and ion entropies display similar rates of increase and that all four entropy rates increase approximately as ε o , consistent with the assumption that the quasilinear premise is valid for the initial conditions assumed for these simulations. The simulations further predict that the time rates of ion entropy increase should be substantially greater for kinetic Alfvén turbulence than for whistler turbulence.

Death During Simulation: A Literature Review.

Science.gov (United States)

Heller, Benjamin J; DeMaria, Samuel; Katz, Daniel; Heller, Joshua A; Goldberg, Andrew T

2016-01-01

One of the goals of simulation is to teach subjects critical skills and knowledge applicable to live encounters, without the risk of harming actual patients. Although simulation education has surged in medical training over the last two decades, several ethically challenging educational methods have arisen. Simulated death has arisen as one of these challenging issues and currently there is no consensus regarding how to best manage this controversial topic in the simulated environment. The goal of this review is to analyze how simulated mortality has been used and discover whether or not this tool is beneficial to learners. In May 2016, the authors performed a literature search on both Pubmed and the Cochrane database using multiple variations of keywords; they then searched bibliographies and related articles. There were 901 articles acquired in the initial search. The authors eliminated articles that were not relevant to the subject matter. After adding articles from bibliographies and related articles, the authors included the 43 articles cited in this article. As a result, the authors of this article believe that death, when used appropriately in simulation, can be an effective teaching tool and can be used in a responsible manner.

Dynamic modeling and simulation of power transformer maintenance costs

Directory of Open Access Journals (Sweden)

Ristić Olga

2016-01-01

Full Text Available The paper presents the dynamic model of maintenance costs of the power transformer functional components. Reliability is modeled combining the exponential and Weibull's distribution. The simulation was performed with the aim of corrective maintenance and installation of the continuous monitoring system of the most critical components. Simulation Dynamic System (SDS method and VENSIM PLE software was used to simulate the cost. In this way, significant savings in maintenance costs will be achieved with a small initial investment. [Projekat Ministarstva nauke Republike Srbije, br. III 41025 i br. OI 171007

Molecular dynamics simulations of oscillatory flows in microfluidic channels

DEFF Research Database (Denmark)

Hansen, J.S.; Ottesen, Johnny T.

2006-01-01

In this paper we apply the direct non-equilibrium molecular dynamics technique to oscillatory flows of fluids in microscopic channels. Initially, we show that the microscopic simulations resemble the macroscopic predictions based on the Navier–Stokes equation very well for large channel width, high...... density and low temperature. Further simulations for high temperature and low density show that the non-slip boundary condition traditionally used in the macroscopic equation is greatly compromised when the fluid–wall interactions are the same as the fluid–fluid interactions. Simulations of a system...

Halo shapes, initial shear field, and cosmic web

International Nuclear Information System (INIS)

Rossi, G

2014-01-01

The ellipsoidal collapse model, combined with the excursion set theory, allows one to estimate the shapes of dark matter halos as seen in high-resolution numerical simulations. The same theoretical framework predicts a quasi-universal behaviour for the conditional axis ratio distributions at later times, set by initial conditions and unaltered by non-linear evolution. The formalism for halo shapes is also useful in making the connection with the initial shear field of the cosmic web, which plays a crucial role in the formation of large-scale structures. The author has briefly discussed the basic aspects of the modelling, as well as the implications of a new formula for the constrained eigenvalues of the initial shear field, given the fact that positions are peaks or dips in the corresponding density field – and not random locations. This formula leads to a new generalized excursion set algorithm for peaks in Gaussian random fields. The results highlighted, here, are relevant for a number of applications, especially for weak lensing studies and for devising algorithms to find and classify structures in the cosmic web

Initial frequency shift of large amplitude plasma wave

International Nuclear Information System (INIS)

Sugihara, Ryo; Yamanaka, Kaoru.

1979-04-01

A distribution function which is an exact solution to the collisionless Boltzmann equation is obtained in an expansion form in terms of the potential phi(x, t). A complex nonlinear frequency shift ωsub( n)(t) is obtained by use of the Poisson equation and the expansion. The theory is valid for arbitrary phi 0 and v sub(p) as long as ωsub(p) >> γsub( l), and in the initial phase defined by 0 0 , v sub(p), ωsub(p), γsub( l) and t sub(c) are the initial value of phi, the phase velocity, the Langmuir frequency, the linear Landau damping coefficient and the time for the first minimum of the amplitude oscillation. The ωsub( n)(0) does not vanish and Reωsub( n)(0)/γsub( l) > 1 holds even for e phi 0 /T 1 in the initial phase for v sub( p) > v sub( t). The theory reproduces main features of experimental results and that of simulations. (author)

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

Theoretical analysis and numerical simulations are shown to demonstrate the validity .... where d0 denotes the dust charge number, j0 represents the equilibrium ... singlet scalar with an additional discrete symmetry Z 2 is introduced to SM.

Simulation Use in Paramedic Education Research (SUPER): A Descriptive Study.

Science.gov (United States)

McKenna, Kim D; Carhart, Elliot; Bercher, Daniel; Spain, Andrew; Todaro, John; Freel, Joann

2015-01-01

The purpose of this research was to characterize the use of simulation in initial paramedic education programs in order assist stakeholders' efforts to target educational initiatives and resources. This group sought to provide a snapshot of what simulation resources programs have or have access to and how they are used; faculty perceptions about simulation; whether program characteristics, resources, or faculty training influence simulation use; and if simulation resources are uniform for patients of all ages. This was a cross-sectional census survey of paramedic programs that were accredited or had a Letter of Review from the Committee on Accreditation of Educational Programs for the EMS Professions at the time of the study. The data were analyzed using descriptive statistics and chi-square analyses. Of the 638 surveys sent, 389 valid responses (61%) were analyzed. Paramedic programs reported they have or have access to a wide range of simulation resources (task trainers [100%], simple manikins [100%], intermediate manikins [99%], advanced/fully programmable manikins [91%], live simulated patients [83%], computer-based [71%], and virtual reality [19%]); however, they do not consistently use them, particularly advanced (71%), live simulated patients (66%), computer-based (games, scenarios) (31%), and virtual reality (4%). Simulation equipment (of any type) reportedly sits idle and unused in (31%) of programs. Lack of training was cited as the most common reason. Personnel support specific to simulation was available in 44% of programs. Programs reported using simulation to replace skills more frequently than to replace field or clinical hours. Simulation goals included assessment, critical thinking, and problem-solving most frequently, and patient and crew safety least often. Programs using advanced manikins report manufacturers as their primary means of training (87%) and that 19% of faculty had no training specific to those manikins. Many (78%) respondents felt

Clinical simulation as an evaluation method in health informatics

DEFF Research Database (Denmark)

Jensen, Sanne

2016-01-01

Safe work processes and information systems are vital in health care. Methods for design of health IT focusing on patient safety are one of many initiatives trying to prevent adverse events. Possible patient safety hazards need to be investigated before health IT is integrated with local clinical...... work practice including other technology and organizational structure. Clinical simulation is ideal for proactive evaluation of new technology for clinical work practice. Clinical simulations involve real end-users as they simulate the use of technology in realistic environments performing realistic...... tasks. Clinical simulation study assesses effects on clinical workflow and enables identification and evaluation of patient safety hazards before implementation at a hospital. Clinical simulation also offers an opportunity to create a space in which healthcare professionals working in different...

Initial-State Graviton Radiation in Quantum Black Hole Production

CERN Document Server

AUTHOR|(CDS)2262067

2017-01-01

Monte Carlo simulation of quantum black hole production in the ATLAS experiment that allows for graviton radiation in the initial state is discussed and studied. It is concluded that, using trapped surface calculations and graviton emission, a black hole signal would be significant for Planck scales up to 4.5 TeV given a proton-proton luminosity of 37 fb$^{-1}$ in the 13 TeV LHC configuration.

FASTBUS simulation tools

International Nuclear Information System (INIS)

Dean, T.D.; Haney, M.J.

1991-10-01

A generalized model of a FASTBUS master is presented. The model is used with simulation tools to aid in the specification, design, and production of FASTBUS slave modules. The model provides a mechanism to interact with the electrical schematics and software models to predict performance. The model is written in the IEEE std 1076-1987 hardware description language VHDL. A model of the ATC logic is also presented. VHDL was chosen to provide portability to various platforms and simulation tools. The models, in conjunction with most commercially available simulators, will perform all of the transactions specified in IEEE std 960-1989. The models may be used to study the behavior of electrical schematics and other software models and detect violations of the FASTBUS protocol. For example, a hardware design of a slave module could be studied, protocol violations detected and corrected before committing money to prototype development. The master model accepts a stream of high level commands from an ASCII file to initiate FASTBUS transactions. The high level command language is based on the FASTBUS standard routines listed in IEEE std 1177-1989. Using this standard-based command language to direct the model of the master, hardware engineers can simulate FASTBUS transactions in the language used by physicists and programmers to operate FASTBUS systems. 15 refs., 6 figs

An Improved Sequential Initiation Method for Multitarget Track in Clutter with Large Noise Measurement

Directory of Open Access Journals (Sweden)

Daxiong Ji

2014-01-01

Full Text Available This paper proposes an improved sequential method for underwater multiple objects tracks initiation in clutter, estimating the initial position for the trajectory. The underwater environment is complex and changeable, and the sonar data are not very ideal. When the detection distance is far, the error of measured data is also great. Besides that, the clutter has a grave effect on the tracks initiation. So it is hard to initialize a track and estimate the initial position. The new tracks initiation is that when at least six of ten points meet the requirements, then we determine that there is a new track and the initial states of the parameters are estimated by the linear least square method. Compared to the conventional tracks initiation methods, our method not only considers the kinematics information of targets, but also regards the error of the sonar sensors as an important element. Computer simulations confirm that the performance of our method is very nice.

α-Tubulin Tyrosination and CLIP-170 Phosphorylation Regulate the Initiation of Dynein-Driven Transport in Neurons

Directory of Open Access Journals (Sweden)

Jeffrey J. Nirschl

2016-03-01

Full Text Available Motor-cargo recruitment to microtubules is often the rate-limiting step of intracellular transport, and defects in this recruitment can cause neurodegenerative disease. Here, we use in vitro reconstitution assays with single-molecule resolution, live-cell transport assays in primary neurons, computational image analysis, and computer simulations to investigate the factors regulating retrograde transport initiation in the distal axon. We find that phosphorylation of the cytoskeletal-organelle linker protein CLIP-170 and post-translational modifications of the microtubule track combine to precisely control the initiation of retrograde transport. Computer simulations of organelle dynamics in the distal axon indicate that while CLIP-170 primarily regulates the time to microtubule encounter, the tyrosination state of the microtubule lattice regulates the likelihood of binding. These mechanisms interact to control transport initiation in the axon in a manner sensitive to the specialized cytoskeletal architecture of the neuron.