Lattice gas simulations of dynamical geometry in two dimensions
NASA Astrophysics Data System (ADS)
Klales, Anna; Cianci, Donato; Needell, Zachary; Meyer, David A.; Love, Peter J.
2010-10-01
We present a hydrodynamic lattice gas model for two-dimensional flows on curved surfaces with dynamical geometry. This model is an extension to two dimensions of the dynamical geometry lattice gas model previously studied in one dimension. We expand upon a variation of the two-dimensional flat space Frisch-Hasslacher-Pomeau (FHP) model created by Frisch [Phys. Rev. Lett.PRLTAO0031-9007 56, 1505 (1986)]10.1103/PhysRevLett.56.1505 and independently by Wolfram, and modified by Boghosian [Philos. Trans. R. Soc. London, Ser. A 360, 333 (2002)]10.1098/rsta.2001.0933. We define a hydrodynamic lattice gas model on an arbitrary triangulation whose flat space limit is the FHP model. Rules that change the geometry are constructed using the Pachner moves, which alter the triangulation but not the topology. We present results on the growth of the number of triangles as a function of time. Simulations show that the number of triangles grows with time as t1/3 , in agreement with a mean-field prediction. We also present preliminary results on the distribution of curvature for a typical triangulation in these simulations.
Lattice gas simulations of dynamical geometry in two dimensions.
Klales, Anna; Cianci, Donato; Needell, Zachary; Meyer, David A; Love, Peter J
2010-10-01
We present a hydrodynamic lattice gas model for two-dimensional flows on curved surfaces with dynamical geometry. This model is an extension to two dimensions of the dynamical geometry lattice gas model previously studied in one dimension. We expand upon a variation of the two-dimensional flat space Frisch-Hasslacher-Pomeau (FHP) model created by Frisch [Phys. Rev. Lett. 56, 1505 (1986)] and independently by Wolfram, and modified by Boghosian [Philos. Trans. R. Soc. London, Ser. A 360, 333 (2002)]. We define a hydrodynamic lattice gas model on an arbitrary triangulation whose flat space limit is the FHP model. Rules that change the geometry are constructed using the Pachner moves, which alter the triangulation but not the topology. We present results on the growth of the number of triangles as a function of time. Simulations show that the number of triangles grows with time as t(1/3), in agreement with a mean-field prediction. We also present preliminary results on the distribution of curvature for a typical triangulation in these simulations.
Lattice gas simulation of experimentally studied evacuation dynamics.
Helbing, Dirk; Isobe, Motonari; Nagatani, Takashi; Takimoto, Kouhei
2003-06-01
We study the evacuation process from a classroom by means of experiments and simulations. The evacuation of students from a classroom is observed by video cameras, and the escape time of each student is measured. Our experimental results are compared with simulations based on a lattice gas model of pedestrian flows. We find that the empirically identified inefficiencies of the evacuation process can be well reproduced. Our particular focus is on the spatial dependence of the escape times on the initial positions, which is highly significant. The escape time distribution turns out to be rather broad due to a jamming (queuing) of the students at the exit, which determines not only the saturation flow (capacity) but also the temporal characteristics of the evacuation dynamics.
Overview: Understanding nucleation phenomena from simulations of lattice gas models
NASA Astrophysics Data System (ADS)
Binder, Kurt; Virnau, Peter
2016-12-01
Monte Carlo simulations of homogeneous and heterogeneous nucleation in Ising/lattice gas models are reviewed with an emphasis on the general insight gained on the mechanisms by which metastable states decay. Attention is paid to the proper distinction of particles that belong to a cluster (droplet), that may trigger a nucleation event, from particles in its environment, a problem crucial near the critical point. Well below the critical point, the lattice structure causes an anisotropy of the interface tension, and hence nonspherical droplet shapes result, making the treatment nontrivial even within the conventional classical theory of homogeneous nucleation. For temperatures below the roughening transition temperature facetted crystals rather than spherical droplets result. The possibility to find nucleation barriers from a thermodynamic analysis avoiding a cluster identification on the particle level is discussed, as well as the question of curvature corrections to the interfacial tension. For the interpretation of heterogeneous nucleation at planar walls, knowledge of contact angles and line tensions is desirable, and methods to extract these quantities from simulations will be mentioned. Finally, also the problem of nucleation near the stability limit of metastable states and the significance of the spinodal curve will be discussed, in the light of simulations of Ising models with medium range interactions.
Overview: Understanding nucleation phenomena from simulations of lattice gas models.
Binder, Kurt; Virnau, Peter
2016-12-07
Monte Carlo simulations of homogeneous and heterogeneous nucleation in Ising/lattice gas models are reviewed with an emphasis on the general insight gained on the mechanisms by which metastable states decay. Attention is paid to the proper distinction of particles that belong to a cluster (droplet), that may trigger a nucleation event, from particles in its environment, a problem crucial near the critical point. Well below the critical point, the lattice structure causes an anisotropy of the interface tension, and hence nonspherical droplet shapes result, making the treatment nontrivial even within the conventional classical theory of homogeneous nucleation. For temperatures below the roughening transition temperature facetted crystals rather than spherical droplets result. The possibility to find nucleation barriers from a thermodynamic analysis avoiding a cluster identification on the particle level is discussed, as well as the question of curvature corrections to the interfacial tension. For the interpretation of heterogeneous nucleation at planar walls, knowledge of contact angles and line tensions is desirable, and methods to extract these quantities from simulations will be mentioned. Finally, also the problem of nucleation near the stability limit of metastable states and the significance of the spinodal curve will be discussed, in the light of simulations of Ising models with medium range interactions.
Lattice gas simulations of dynamical geometry in one dimension.
Love, Peter J; Boghosian, Bruce M; Meyer, David A
2004-08-15
We present numerical results obtained using a lattice gas model with dynamical geometry. The (irreversible) macroscopic behaviour of the geometry (size) of the lattice is discussed in terms of a simple scaling theory and obtained numerically. The emergence of irreversible behaviour from the reversible microscopic lattice gas rules is discussed in terms of the constraint that the macroscopic evolution be reproducible. The average size of the lattice exhibits power-law growth with exponent at late times. The deviation of the macroscopic behaviour from reproducibility for particular initial conditions ('rogue states') is investigated as a function of system size. The number of such 'rogue states' is observed to decrease with increasing system size. Two mean-field analyses of the macroscopic behaviour are also presented. Copyright 2004 The Royal Society
Diemer, K.L.
1992-01-01
Lattice gas automata models for hydrodynamics offer a method for simulating fluids in between the standard molecular dynamic models and finite difference schemes. The algorithm is especially suited to low Mach number flow around complex boundaries and can be implemented in a fully parallelizable, memory efficient manner using only boolean operations. The simplest lattice gas automata is reviewed. The modification of the standard Chapmann-Enskog expansion lattice gas case is reviewed. In the long wavelength and long time limit, the incompressible Navier-Stokes equation is derived. Analytic calculations of shear viscosity [eta], mean free path [lambda], and a reduced Reynolds number R are presented for a number of 2D and 3D lattice gas models. Comparisons of lattice gas results with analytical predictions and other numerical methods are reviewed. This is followed by a discussion of the zero velocity limit used in deriving the above analytic results. Lattice gas hydrodynamic models for flows through porous media in two and three dimensions are described. The computational method easily handles arbitrary boundaries and a large range of Reynolds numbers. Darcy's law is confirmed for Poiseuille flow and for complicated boundary flows. Lattice gas simulation results for permeability for one geometry are compared with experimental results and found to agree to within 10%. Lattice gas hydrodynamic models for two dimensional binary fluids are described. The scaling of the correlation function during late stage growth is examined. The domain growth kinetics during this period is also explored and compared with the work of Furukawa. A local lattice gas model for binary fluids with an adjustable parameter [lambda] which allows degree of miscibility is introduced. For [lambda] < [lambda][sub c] the fluids are immiscible while for [lambda] > [lambda][sub c] the fluids are miscible. Theoretical and numerical studies on the diffusive properties of this lattice gas are presented.
Simulation of two-phase flow using lattice gas automata methods
Tsumaya, Akira; Ohashi, Hirotada; Akiyama, Mamoru
1996-08-01
Two-phase flow simulation has been primarily based on experimental data in the sense that constitutive relations necessary for solving fundamental equations are experimentally determined. This assures validity of simulation of two-phase flow within the experimental conditions, but it is difficult to predict the behavior of two-phase flow under extreme or complex conditions which occur, for example, in severe accidents of nuclear reactors. Lattice gas automaton (LGA) simulation has recently attracted attention as a method for numerical simulation of multi phase flow. The authors extend phase-separation LGA models and develop methods for two-phase flow simulation. First, they newly added a flow model to the immiscible lattice gas model and applied it to two-dimensional Poiseuille flow. They obtained a result looking like lubricated pipelining of crude oil with water. Also, considering the gravity effect, they introduced a buoyancy force into the liquid-gas model. As a result, they demonstrated that gas bubbles of various diameters rise and gradually coalesce each other turning into larger bubbles. Using these newly developed LGA models, they succeeded in simulating various flow patterns of two-phase flow.
Pair interaction lattice gas simulations: Flow past obstacles in two and three dimensions
Vogeler, A.; Wolf-Gladrow, D.A. )
1993-04-01
Apart from the FCHC (face-centered hypercube), Nasilowski's pair interaction lattice gas (PI) is the only known lattice gas automaton for three-dimensional hydrodynamic simulations. Unfortunately, the viscosity of PI is not isotropic. In order to determine the degree anisotropy, the authors derive fluid dynamic equations for the regime of compressible viscid flow. From relaxation measurements of waves propagating in various directions they compute the physically relevant dissipation coefficients and compare their results with theoretical predictions. Although PI shows a high degree of anisotropy, they define the mean value of the dissipation tensor as effective shear viscosity. Using this value of v[sub eff][sup 2D] = 0.35, two-dimensional simulations of flow past a cylinder yield drag coefficients in quantitative agreement with wind tunnel measurements over a range of Reynolds numbers of 5-50. Three-dimensional simulations of flow past a sphere yield qualitative agreement with various references. A fit of the results to a semi-empirical curve provides an effective value of v[sub eff][sup 2D] = 0.21 for a range of Reynolds numbers from 0.19 to 40. In order to check for finite-size effects, the authors measured the mean free path [lambda] and computed the Knudsen numbers. They obtained [lambda] [approx]1 lattice unit, corresponding to Kn = 0.01 (2D) and Kn = 0.1 (3D). They found no significant finite-size effects. 44 refs., 10 figs.
Simulating the time-dependent Schr"odinger equation with a quantum lattice-gas algorithm
NASA Astrophysics Data System (ADS)
Prezkuta, Zachary; Coffey, Mark
2007-03-01
Quantum computing algorithms promise remarkable improvements in speed or memory for certain applications. Currently, the Type II (or hybrid) quantum computer is the most feasible to build. This consists of a large number of small Type I (pure) quantum computers that compute with quantum logic, but communicate with nearest neighbors in a classical way. The arrangement thus formed is suitable for computations that execute a quantum lattice gas algorithm (QLGA). We report QLGA simulations for both the linear and nonlinear time-dependent Schr"odinger equation. These evidence the stable, efficient, and at least second order convergent properties of the algorithm. The simulation capability provides a computational tool for applications in nonlinear optics, superconducting and superfluid materials, Bose-Einstein condensates, and elsewhere.
Simulation of pore scale porous media flow using lattice gas methods
NASA Astrophysics Data System (ADS)
Eggert, K.; Chen, Shiyi; Travis, B.; Grunau, D.; Loh, E.; Kovarik, F.
Carbon dioxide-foam injection is an important technique for improving the recovery of oil from porous rocks. Huh, et. al. (1989) recently presented results of two-dimensional laboratory micromodel studies conducted to better understand this process for improved oil recovery. These experimental results indicate that the introduction of CO2 foam may be expected to have a substantial effect on the relative permeability curves that would be used to model improved oil recovery in a reservoir. However, in order to determine expected changes in relative permeability a computational technique is required to quantify the experimental results, and to help determine the appropriate relative permeability curves for reservoir scale calculation. Two computational methodologies are needed to utilize the experimental information to improve reservoir simulations. First, a method is needed for quantitatively describing the phenomena observed in the micromodel geometry. Second, a method is needed to extend these effects to the different scales of heterogeneity that may be expected to exist between the laboratory and the field. The focus is on the first of these methods, and although it does not yet fully solve the problem of representing these fluid systems in the laboratory, it presents a promising approach to this problem. The application of the lattice gas method is discussed for solution of the nondimensional Navier-Stokes equations for flow of fluids through the complex microscopic geometry of porous media. In particular, the approach presented allows the simulation not only of single fluids through the media, but of systems of two or more fluids ranging from fully miscible to completely immiscible.
Simulation of pore scale porous media flow using lattice gas methods
Eggert, K.; Chen, Shiyi; Travis, B.; Grunau, D. ); Loh, E. ); Kovarik, F. . Inst. for Improved Oil Recovery Research)
1991-01-01
Carbon dioxide-foam injection is an important technique for improving the recovery of oil from porous rocks. Huh, et. al. (1989) recently presented results of two-dimensional laboratory micromodel studies conducted to better understand this process for improved oil recovery. These experimental results indicate that the introduction of CO{sub 2} foam may be expected to have a substantial effect on the relative permeability curves that would be used to model improved oil recovery in a reservoir. However, in order to determine expected changes in relative permeability a computational technique is require to quantify the experimental results, and to help determine the appropriate relative permeability curves for reservoir scale calculation. Two computational methodologies are needed to utilize the experimental information to improve reservoir simulations. First, a method is needed for quantitatively describing the phenomena observed in the micromodel geometry. Second, a method is needed to extend these effects to the different scales of heterogeneity that may be expected to exist between the laboratory and the field. This paper is focused on the first of these methods, and although it does not yet fully solve the problem of representing these fluid systems in the laboratory, it presents a promising approach to this problem. The paper briefly discusses the application of the lattice gas method for solution of the nondimensional Navier-Stokes equations for flow of fluids through the complex microscopic geometry of porous media. In particular, the approach presented herein allows the simulation not only of single fluids through the media, but of systems of two or more fluids ranging from fully miscible to completely immiscible. 11 refs., 4 figs.
``SAFFMAN-TAYLOR'' Finger in 2d Parallel Viscous: BGK Lattice Gas Simulations
NASA Astrophysics Data System (ADS)
Salin, Dominique; Rakotomalala, Nicole; Watzky, Philippe
1996-11-01
We study the displacement of miscible fluids between two parallel plates for different values of the Peclet number Pe and of the viscosity ratio M. The full Navier-Stokes problem is addressed. We use the BGK lattice gas method, which is well suited for miscible fluids and allows to introduce molecular diffusion at the microscopic scale of the lattice. This numerical experiment leads to a symmetric concentration profile about the middle of the gap between the plates. At Pe numbers of the order of 1, mixing involves diffusion and advection in the flow direction. At large Pe, the fluids do not mix and an interface between them can be defined. Moreover, above M ~ 10, the interface becomes a well defined finger, the reduced width of which tends to λ_∞=0.56 at large values of M. Assuming that miscible fluids at high Pe numbers are similar to immiscible fluids at high capillary numbers, we find the analytical shape of the finger, using an extrapolation of the Reinelt-Saffman calculations for a Stokes immiscible flow. Surprisingly, the result is that our finger can be deduced from the celebrated Saffman-Taylor' s one, obtained in a potential flow, by a streching in the flow direction by a numerical factor of 2.125.
NASA Astrophysics Data System (ADS)
Alber, Mark S.; Kiskowski, Maria; Jiang, Yi; Newman, Stuart
Modelling pattern formation and morphogenesis are fundamental problems in biology. One useful approach is lattice gas cellular automata (LGCA) model. This paper reviews several stochastic lattice gas models for pattern formation in myxobacteria fruiting body morphogenesis and vertebrate limb skeletogenesis. The fruiting body formation in myxobacteria is a complex morphological process that requires the organized, collective effort of tens of thousands of cells. It provides new insight into collective microbial behavior since myxobacteria morphogenic pattern formation is governed by cell-cell interactions rather than chemotaxis. We describe LGCA models for the aggregation stage of the fruiting body formation. Limb bud precartilage mesenchymal cells in micromass culture undergo chondrogenic pattern formation, which results in the formation of regularly-spaced "islands" of cartilage analogous to the cartilage primordia of the developing limb skeleton. An LGCA model, based on reaction-diffusion coupling and cell-matrix adhesion, is described for this process.
Counting Lattice-Gas Invariants
2007-11-02
Dominique d’Humières, Brosl Hasslacher, Pierre Lallemand, Yves Pomeau, and Jean-Pierre Rivet . Lattice gas hydrodynamics in two and three dimensions...177. Springer -Verlag, Februrary 1989. Proceedings of the Winter School, Les Houches, France. 6
NASA Astrophysics Data System (ADS)
Ahmad, Waqar; Parvez, M.; Baloach, Musa Kaleem; Qaisrani, A. U.; Khalid, M.
2006-11-01
The kinetics of an irreversible dimer-trimer reaction of the type 3A 2 + 2B 3 → 6AB have been studied using a non-thermal (precursor mechanism) model on a square as well as on a hexagonal lattice surface by Monte Carlo simulation. When the range of the precursors (A atoms) is increased, the model gives production rates (reactive window widths) that are quite large as compared with those for thermal (Langmuir-Hanshelwood mechanism) model. The phase diagrams qualitatively resemble with the standard ZGB model except that the continuous transition point is eliminated when the range of the precursors is extended up to the third nearest neighbourhood. The diffusion of A atoms on the surface as well as their desorption from the surface with a certain probability is also considered to see their effects on the reaction mechanism.
NASA Astrophysics Data System (ADS)
Liu, Da-Jiang; Evans, James W.
2013-12-01
A realistic molecular-level description of catalytic reactions on single-crystal metal surfaces can be provided by stochastic multisite lattice-gas (msLG) models. This approach has general applicability, although in this report, we will focus on the example of CO-oxidation on the unreconstructed fcc metal (1 0 0) or M(1 0 0) surfaces of common catalyst metals M = Pd, Rh, Pt and Ir (i.e., avoiding regimes where Pt and Ir reconstruct). These models can capture the thermodynamics and kinetics of adsorbed layers for the individual reactants species, such as CO/M(1 0 0) and O/M(1 0 0), as well as the interaction and reaction between different reactant species in mixed adlayers, such as (CO + O)/M(1 0 0). The msLG models allow population of any of hollow, bridge, and top sites. This enables a more flexible and realistic description of adsorption and adlayer ordering, as well as of reaction configurations and configuration-dependent barriers. Adspecies adsorption and interaction energies, as well as barriers for various processes, constitute key model input. The choice of these energies is guided by experimental observations, as well as by extensive Density Functional Theory analysis. Model behavior is assessed via Kinetic Monte Carlo (KMC) simulation. We also address the simulation challenges and theoretical ramifications associated with very rapid diffusion and local equilibration of reactant adspecies such as CO. These msLG models are applied to describe adsorption, ordering, and temperature programmed desorption (TPD) for individual CO/M(1 0 0) and O/M(1 0 0) reactant adlayers. In addition, they are also applied to predict mixed (CO + O)/M(1 0 0) adlayer structure on the nanoscale, the complete bifurcation diagram for reactive steady-states under continuous flow conditions, temperature programmed reaction (TPR) spectra, and titration reactions for the CO-oxidation reaction. Extensive and reasonably successful comparison of model predictions is made with experimental
Noise and compressibility in lattice-gas fluids
NASA Technical Reports Server (NTRS)
Dahlburg, Jill P.; Montgomery, David; Doolen, Gary D.
1987-01-01
Computations are reported in which the hexagonal lattice gas is used to simulate two-dimensional Navier-Stokes shear flows. Limitations associated with noise in the initial loading and compressible effects associated with a velocity-dependent equation of state arise and interact with each other. A relatively narrow window in density and flow speed exhibits physical behavior.
Quantum lattice gas algorithm for the telegraph equation.
Coffey, Mark W; Colburn, Gabriel G
2009-06-01
The telegraph equation combines features of both the diffusion and wave equations and has many applications to heat propagation, transport in disordered media, and elsewhere. We describe a quantum lattice gas algorithm (QLGA) for this partial differential equation with one spatial dimension. This algorithm generalizes one previously known for the diffusion equation. We present an analysis of the algorithm and accompanying simulation results. The QLGA is suitable for simulation on combined classical-quantum computers.
Lattice gas hydrodynamics in two and three dimensions
Frisch, U.; d'Humieres, D.; Hasslacher, B.; Lallemand, P.; Pomeau, Y.; Rivet, J.P.
1986-01-01
Hydrodynamical phenomena can be simulated by discrete lattice gas models obeing cellular automata rules (U. Frisch, B. Hasslacher, and Y. Pomeau, Phys. Rev. Lett. 56, 1505, (1986); D. d'Humieres, P. Lallemand, and U. Frisch, Europhys. Lett. 2, 291, (1986)). It is here shown for a class of D-dimensional lattice gas models how the macrodynamical (large-scale) equations for the densities of microscopically conserved quantities can be systematically derived from the underlying exact ''microdynamical'' Boolean equations. With suitable restrictions on the crystallographic symmetries of the lattice and after proper limits are taken, various standard fluid dynamical equations are obtained, including the incompressible Navier-Stokes equations in two and three dimensions. The transport coefficients appearing in the macrodynamical equations are obtained using variants of fluctuation-dissipation and Boltzmann formalisms adapted to fully discrete situations.
Lattice gas methods for computational aeroacoustics
NASA Technical Reports Server (NTRS)
Sparrow, Victor W.
1995-01-01
This paper presents the lattice gas solution to the category 1 problems of the ICASE/LaRC Workshop on Benchmark Problems in Computational Aeroacoustics. The first and second problems were solved for Delta t = Delta x = 1, and additionally the second problem was solved for Delta t = 1/4 and Delta x = 1/2. The results are striking: even for these large time and space grids the lattice gas numerical solutions are almost indistinguishable from the analytical solutions. A simple bug in the Mathematica code was found in the solutions submitted for comparison, and the comparison plots shown at the end of this volume show the bug. An Appendix to the present paper shows an example lattice gas solution with and without the bug.
Measurement-based quantum lattice gas model of fluid dynamics in 2+1 dimensions.
Micci, Michael M; Yepez, Jeffrey
2015-09-01
Presented are quantum simulation results using a measurement-based quantum lattice gas algorithm for Navier-Stokes fluid dynamics in 2+1 dimensions. Numerical prediction of the kinematic viscosity was measured by the decay rate of an initial sinusoidal flow profile. Due to local quantum entanglement in the quantum lattice gas, the minimum kinematic viscosity in the measurement-based quantum lattice gas is lower than achievable in a classical lattice gas. The numerically predicted viscosities precisely match the theoretical predictions obtained with a mean field approximation. Uniform flow profile with double shear layers, on a 16K×8K lattice, leads to the Kelvin-Helmholtz instability, breaking up the shear layer into pairs of counter-rotating vortices that eventually merge via vortex fusion and dissipate because of the nonzero shear viscosity.
A lattice gas model for thermohydrodynamics
Chen, Shiyi; Chen, Hudong; Doolen, G.D.; Gutman, S.; Lee, M.
1990-05-03
The FHP lattice gas model is extended to include a temperature variable in order to study thermohydrodynamics. The compressible Navier-Stokes equations are derived using a Chapman-Enskog expansion. Heat conduction and convention problems are investigated, including Benard convention. It is shown that the usual FHP rescaling procedure can be avoided by controlling the temperature. 20 refs., 12 figs.
Lattice gas models with long range interactions
NASA Astrophysics Data System (ADS)
Aristoff, David; Zhu, Lingjiong
2017-02-01
We study microcanonical lattice gas models with long range interactions, including power law interactions. We rigorously obtain a variational principle for the entropy. In a one dimensional example, we find a first order phase transition by proving the entropy is non-differentiable along a certain curve.
An Overview of Lattice-Gas Dynamics
1997-11-01
irreversible. There- fore, the CAM-8 dissipates heat like any conventional computer even though the Szilard entropy of the lattice gas is unchanged, but an...Reviews of Modern Physics, 49(3):435–479, 1977. [37] Leo P. Kadanoff and Jack Swift. Transport coefficients near the critical point: A master-equation
Multisite Interactions in Lattice-Gas Models
NASA Astrophysics Data System (ADS)
Einstein, T. L.; Sathiyanarayanan, R.
For detailed applications of lattice-gas models to surface systems, multisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We recall that trio (3-adatom, non-pairwise) interactions do not inevitably create phase boundary asymmetries about half coverage. We discuss a sophisticated application to an experimental system and describe refinements in extracting lattice-gas energies from calculations of total energies of several different ordered overlayers. We describe how lateral relaxations complicate matters when there is direct interaction between the adatoms, an issue that is important when examining the angular dependence of step line tensions. We discuss the connector model as an alternative viewpoint and close with a brief account of recent work on organic molecule overlayers.
Edison, John R; Monson, Peter A
2013-06-21
This article addresses the accuracy of a dynamic mean field theory (DMFT) for fluids in porous materials [P. A. Monson, J. Chem. Phys. 128, 084701 (2008)]. The theory is used to study the relaxation processes of fluids in pores driven by step changes made to a bulk reservoir in contact with the pore. We compare the results of the DMFT to those obtained by averaging over large numbers of dynamic Monte Carlo (DMC) simulation trajectories. The problem chosen for comparison is capillary condensation in slit pores, driven by step changes in the chemical potential in the bulk reservoir and involving a nucleation process via the formation of a liquid bridge. The principal difference between the DMFT results and DMC is the replacement of a distribution of nucleation times and location along the pore for the formation of liquid bridges by a single time and location. DMFT is seen to yield an otherwise qualitatively accurate description of the dynamic behavior.
NASA Astrophysics Data System (ADS)
Edison, John R.; Monson, Peter A.
2013-06-01
This article addresses the accuracy of a dynamic mean field theory (DMFT) for fluids in porous materials [P. A. Monson, J. Chem. Phys. 128, 084701 (2008)], 10.1063/1.2837287. The theory is used to study the relaxation processes of fluids in pores driven by step changes made to a bulk reservoir in contact with the pore. We compare the results of the DMFT to those obtained by averaging over large numbers of dynamic Monte Carlo (DMC) simulation trajectories. The problem chosen for comparison is capillary condensation in slit pores, driven by step changes in the chemical potential in the bulk reservoir and involving a nucleation process via the formation of a liquid bridge. The principal difference between the DMFT results and DMC is the replacement of a distribution of nucleation times and location along the pore for the formation of liquid bridges by a single time and location. DMFT is seen to yield an otherwise qualitatively accurate description of the dynamic behavior.
Dynamic lattice-gas model of underpotential deposition
NASA Astrophysics Data System (ADS)
Brown, Gregory; Rikvold, Per Arne; Novotny, M. A.; Wieckowski, Andrzej
1998-03-01
Underpotential deposition (UPD) is the process by which a monolayer or less of one metal is adsorbed onto the surface of another at electrode potentials more positive than those at which bulk deposition occurs. For particular combinations of metals, lattice-gas models have been formulated and studied using both analytical and numerical techniques. Dynamic Monte Carlo simulations of a lattice-gas model of UPD of copper onto Au(111) in the presence of sulfuric acid are presented. The simulations include adsorption, desorption, and lateral diffusion and span timescales from 10-9 to 10^1 s. The results reproduce the strong asymmetry seen in experimental current profiles that occur after a sudden potential change.(M. H. Hölzle, et al.), J. Electroanal. Chem. \\underbar371, 101 (1994). The simulation technique can also be used to understand features in cyclic-voltammetry profiles, where the applied potential is changed continuously.
High-performance multiprocessor architecture for a 3-D lattice gas model
NASA Technical Reports Server (NTRS)
Lee, F.; Flynn, M.; Morf, M.
1991-01-01
The lattice gas method has recently emerged as a promising discrete particle simulation method in areas such as fluid dynamics. We present a very high-performance scalable multiprocessor architecture, called ALGE, proposed for the simulation of a realistic 3-D lattice gas model, Henon's 24-bit FCHC isometric model. Each of these VLSI processors is as powerful as a CRAY-2 for this application. ALGE is scalable in the sense that it achieves linear speedup for both fixed and increasing problem sizes with more processors. The core computation of a lattice gas model consists of many repetitions of two alternating phases: particle collision and propagation. Functional decomposition by symmetry group and virtual move are the respective keys to efficient implementation of collision and propagation.
Quantum learning for a quantum lattice gas computer
NASA Astrophysics Data System (ADS)
Behrman, Elizabeth; Steck, James
2015-03-01
Quantum lattice gas is the logical generalization of quantum cellular automata. In low energy the dynamics are well described by the Gross-Pitaevskii equation in the mean field limit, which is an effective nonlinear interaction model of a Bose-Einstein condensate. In previous work, we have shown in simulation that both spatial and temporal models of quantum learning computers can be used to ``design'' non-trivial quantum algorithms. The advantages of quantum learning over the usual practice of using quantum gate building blocks are, first, the rapidity with which the problem can be solved, without having to decompose the problem; second, the fact that our technique can be used readily even when the problem, or the operator, is not well understood; and, third, that because the interactions are a natural part of the physical system, connectivity is automatic. The advantage to quantum learning obviously grows with the size and the complexity of the problem. We develop and present our learning algorithm as applied to the mean field lattice gas equation, and present a few preliminary results.
Quantum learning in a quantum lattice gas computer
NASA Astrophysics Data System (ADS)
Behrman, Elizabeth; Steck, James
2015-04-01
Quantum lattice gas is the logical generalization of quantum cellular automata. At low energy the dynamics are well described by the Gross-Pitaevskii equation in the mean field limit, which is an effective nonlinear interaction model of a Bose-Einstein condensate. In previous work, we have shown in simulation that both spatial and temporal models of quantum learning computers can be used to ``design'' non-trivial quantum algorithms. The advantages of quantum learning over the usual practice of using quantum gate building blocks are, first, the rapidity with which the problem can be solved, without having to decompose the problem; second, the fact that our technique can be used readily even when the problem, or the operator, is not well understood; and, third, that because the interactions are a natural part of the physical system, connectivity is automatic. The advantage to quantum learning obviously grows with the size and the complexity of the problem. We develop and present our learning algorithm as applied to the mean field lattice gas equation, and present a few preliminary results.
Gradient Driven Flow: Lattice Gas, Diffusion Equation and Measurement Scales
2001-01-01
03-200 1 Journal Article (refereed) 2001 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Gradient Driven Flow : Lattice Gas, Diffusion Equation and...time regime, the collective motion exhibits an onset of oscillation. 15. SUBJECT TERMS Diffusion; Fick’s Law; Gradient Driven Flow ; Lattice Gas 16...Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 20010907 062 Gradient driven flow : lattice gas, diffusion equation and measurement scales R.B
A lattice-gas model for amyloid fibril aggregation
Hong, Liu; Qi, Xianghong; Zhang, Yang
2012-01-01
A simple lattice-gas model, with two fundamental energy terms —elongation and nucleation effects, is proposed for understanding the mechanisms of amyloid fibril formation. Based on the analytical solution and Monte Carlo simulation of 1D system, we have thoroughly explored the dependence of mass concentration, number concentration of amyloid filaments and the lag-time on the initial protein concentration, the critical nucleus size, the strengths of nucleation and elongation effects, respectively. We also found that thickening process (self-association of filaments into multi-strand fibrils) is not essential for the modeling of amyloid filaments through simulations on 2D lattice. Compared with the kinetic model recently proposed by Knowles et al., highly quantitative consistency of two models in the calculation of mass fraction of filaments is found. Moreover our model can generate a better prediction on the number fraction, which is closer to experimental values when the elongation strength gets stronger. PMID:23275684
Lattice gas dynamics under continuous measurement
NASA Astrophysics Data System (ADS)
Patil, Yogesh Sharad; Cheung, Hil F. H.; Madjarov, Ivaylo S.; Chen, Huiyao Y.; Vengalattore, Mukund
2016-05-01
The act of measurement has a profound consequences quantum systems. While this backaction has so far been discussed as being a limitation on the precision of measurements, it is increasingly being appreciated that measurement backaction is a powerful and versatile means of quantum control. We have previously demonstrated that backaction from position measurement can modify the coherent tunneling rate of a lattice gas through the Quantum Zeno effect. Here, we show how spatially designed measurement landscapes can be used to realize entropy segregation in lattice gases. This presents an alternate path to the longstanding challenge of realizing lattice gases with sufficiently low entropy to access regimes of correlated quantum behavior such as Néel ordered states. This work is supported by the ARO MURI on non-equilibrium dynamics.
Dynamic behavior of multirobot systems using lattice gas automata
NASA Astrophysics Data System (ADS)
Stantz, Keith M.; Cameron, Stewart M.; Robinett, Rush D., III; Trahan, Michael W.; Wagner, John S.
1999-07-01
Recent attention has been given to the deployment of an adaptable sensor array realized by multi-robotic systems (or swarms). Our group has been studying the collective, autonomous behavior of these such systems and their applications in the area of remote-sensing and emerging threats. To accomplish such tasks, an interdisciplinary research effort at Sandia National Laboratories are conducting tests in the fields of sensor technology, robotics, and multi- agents architectures. Our goal is to coordinate a constellation of point sensors using unmanned robotic vehicles (e.g., RATLERs, Robotic All-Terrain Lunar Exploration Rover- class vehicles) that optimizes spatial coverage and multivariate signal analysis. An overall design methodology evolves complex collective behaviors realized through local interaction (kinetic) physics and artificial intelligence. Learning objectives incorporate real-time operational responses to environmental changes. This paper focuses on our recent work understanding the dynamics of many-body systems according to the physics-based hydrodynamic model of lattice gas automata. Three design features are investigated. One, for single-speed robots, a hexagonal nearest-neighbor interaction topology is necessary to preserve standard hydrodynamic flow. Two, adaptability, defined by the swarm's rate of deformation, can be controlled through the hydrodynamic viscosity term, which, in turn, is defined by the local robotic interaction rules. Three, due to the inherent nonlinearity of the dynamical equations describing large ensembles, stability criteria ensuring convergence to equilibrium states is developed by scaling information flow rates relative to a swarm's hydrodynamic flow rate. An initial test case simulates a swarm of twenty-five robots maneuvering past an obstacle while following a moving target. A genetic algorithm optimizes applied nearest-neighbor forces in each of five spatial regions distributed over the simulation domain. Armed with
A (reactive) lattice-gas approach to economic cycles
NASA Astrophysics Data System (ADS)
Ausloos, Marcel; Clippe, Paulette; Miśkiewicz, Janusz; Peķalski, Andrzej
2004-12-01
A microscopic approach to macroeconomic features is intended. A model for macroeconomic behavior under heterogeneous spatial economic conditions is reviewed. A birth-death lattice gas model taking into account the influence of an economic environment on the fitness and concentration evolution of economic entities is numerically and analytically examined. The reaction-diffusion model can also be mapped onto a high-order logistic map. The role of the selection pressure along various dynamics with entity diffusion on a square symmetry lattice has been studied by Monte-Carlo simulation. The model leads to a sort of phase transition for the fitness gap as a function of the selection pressure and to cycles. The control parameter is a (scalar) “business plan”. The business plan(s) allows for spin-offs or merging and enterprise survival evolution law(s), whence bifurcations, cycles and chaotic behavior.
Residual entropy and waterlike anomalies in the repulsive one dimensional lattice gas
Silva, Fernando Barbosa V. da; Oliveira, Fernando Albuquerque; Barbosa, Marco Aurélio A.
2015-04-14
The thermodynamics and kinetics of the one dimensional lattice gas with repulsive interaction are investigated using transfer matrix technique and Monte Carlo simulations. This simple model is shown to exhibit waterlike anomalies in density, thermal expansion coefficient, and self-diffusion. An unified description for the thermodynamic anomalies in this model is achieved based on the ground state residual entropy which appears in the model due to mixing entropy in a ground state phase transition.
Dynamics of a lattice gas system of three species
NASA Astrophysics Data System (ADS)
Wang, Yuanshi; Wu, Hong; Liang, Junhao
2016-10-01
This paper considers a mutualism system of three species in which each species provides resource for the next one in a one-directional loop, while there exists spatial competition among them. The system is characterized by a lattice gas model and the cases of obligate mutualisms, obligate-facultative mutualisms and facultative mutualisms are considered. Using dynamical systems theory, it is shown that (i) the mutualisms can lead to coexistence of species; (ii) A weak mutualism or an extremely strong mutualism will result in extinction of species, while even the superior facultative species will be driven into extinction by its over-strong mutualism on the next one; (iii) Initial population density plays a role in the coexistence of species. It is also shown that when there exists weak mutualism, an obligate species can survive by providing more benefit to the next one, and the inferior facultative species will not be driven into extinction if it can strengthen its mutualism on the next species. Moreover, Hopf bifurcation, saddle-node bifurcation and bifurcation of heteroclinic cycles are shown in the system. Projection method is extended to exhibit bistability in the three-dimensional model: when saddle-node bifurcation occurs, stable manifold of the saddle-node point divides intR+3 into two basins of attraction of two equilibria. Furthermore, Lyapunov method is applied to exhibit unstability of heteroclinic cycles. Numerical simulations confirm and extend our results.
Shim, Jae Wan; Gatignol, Renée
2010-04-01
We show that the heat exchange between fluid particles and boundary walls can be achieved by controlling the velocity change rate following the particles' collision with a wall in discrete kinetic theory, such as the lattice-gas cellular automata and the lattice Boltzmann method. We derive a relation between the velocity change rate and temperature so that we can control the velocity change rate according to a given temperature boundary condition. This relation enables us to deal with the thermal boundary whose temperature varies along a wall in contrast to the previous works of the lattice-gas cellular automata. In addition, we present simulation results to compare our method to the existing and give an example in a microchannel with a high temperature gradient boundary condition by the lattice-gas cellular automata.
Transport of a lattice gas under continuous measurement
NASA Astrophysics Data System (ADS)
Cheung, Hil F. H.; Patil, Yogesh Sharad; Madjarov, Ivaylo S.; Chen, Huiyao Y.; Vengalattore, Mukund
2016-05-01
The act of measurement has a profound consequence on a quantum system. While this backaction has hitherto been discussed as a limitation to the precision of measurements, it is increasingly being appreciated that measurement backaction is a powerful means of quantum control. We have previously demonstrated that backaction from position measurement can modify the coherent tunneling rate of a lattice gas through the Quantum Zeno effect. By suitably designing measurement landscapes we can control the transport properties of the lattice gas. We describe a quantitative study of lattice gas dynamics under continuous quantum measurement in the context of a quantum to classical transition where the atom dynamics goes from a quantum walk at low measurement strengths to classical diffusion at high measurement strengths. We further discuss the prospect of using disorder measurement landscapes to realize a new form of Anderson localization. This work is supported by the ARO MURI on non-equilibrium dynamics.
Theory of multicolor lattice gas - A cellular automaton Poisson solver
NASA Technical Reports Server (NTRS)
Chen, H.; Matthaeus, W. H.; Klein, L. W.
1990-01-01
The present class of models for cellular automata involving a quiescent hydrodynamic lattice gas with multiple-valued passive labels termed 'colors', the lattice collisions change individual particle colors while preserving net color. The rigorous proofs of the multicolor lattice gases' essential features are rendered more tractable by an equivalent subparticle representation in which the color is represented by underlying two-state 'spins'. Schemes for the introduction of Dirichlet and Neumann boundary conditions are described, and two illustrative numerical test cases are used to verify the theory. The lattice gas model is equivalent to a Poisson equation solution.
The Classical Lattice-Gas Method
1999-02-01
also be fixed obstacles with which the particles have perfectly elastic collisions. For example, one can simulate vortex shedding in a fluid flowing ...cause an attractive force between particles giving rise to an athermal liquid-gas phase transition.4 To simulate the correct macroscopic dynamics , the...rheology of mul- tiphase dynamics is driven by low Reynolds number flows . The rheology of droplets (for example 3 The first lattice Boltzmann simulations
Local lattice-gas model for immiscible fluids
NASA Technical Reports Server (NTRS)
Chen, S.; Doolen, G. D.; Eggert, K.; Grunau, D.; Loh, E. Y.
1991-01-01
A lattice-gas model is presented for two-dimensional immiscible fluid flows with surface tension that uses strictly local collision rules. Instead of using a local total color flux as Somers and Rem (1991), local colored holes are used to be the memory of particles of the same color. Interactions between walls and fluids are included that produce arbitrary contact angles.
A lattice gas cellular automaton approach to model volcanic eruptions
NASA Astrophysics Data System (ADS)
Sanchez, L.; Shcherbakov, R.
2011-12-01
Volcanic eruptions are the result of complex mechanisms that operate in a magma chamber within the crust. In a previous study, we showed that the dynamics of eruptions on Earth are the same and are quite independent of the location and type of volcanism. The goal of this study is to test the universality of volcanism by designing a simple, general model to simulate processes occurring within a magma chamber. We aim at reproducing the threshold behavior that operates in the magma chamber when pressure increase leads to an eruption. To simulate volcanic eruptions, we propose to use a lattice gas cellular automata (LGCA), which have been proven efficient to simulate fluid flow behavior. This type cellular automaton is a discrete dynamical model in space and time, where the fluid is represented at the microscopic level by discrete particles. We start with the simplest LGCA: the 2-dimensional HPP model (proposed in 1973 by Hardy, de Pazzis and Pomeau), which consists of a square lattice where particles interact with one another mimicking the fluid flow and conserving mass and momentum. We also consider the model on a hexagonal lattice to take anisotropy into account. In this model, magma propagates through a heterogeneous medium, and deformation and fracturing occurs on the walls of the chamber up until a pressure threshold is reached and an eruption or a cascade of eruptions occur. We record the size of each event and the number of time steps between consecutive events (or interevent time). The model simulation results for a large number of realizations are compared with observed data. The observations come from eruption records of 13 individual volcanoes located around the world as well as 11 groups of volcanoes located in various regions surrounded by different tectonic settings. From these, we computed the frequency-size distribution of eruptions and the interevent time distributions for a large number of active volcanoes on Earth. This model allows us to study a
High-density equation of state for a lattice gas.
Ushcats, M V
2015-05-01
For the lattice gas models of arbitrary geometry and dimensions with absolute repulsion between particles at zero distance (a hard core identical to a single lattice site) and arbitrary repulsion or attraction at other distances, the "hole-particle" symmetry of the system potential energy has been stated and an equation of state has been derived on the basis of the classical Gibbs statistics. The equation is completely analogous to the well-known virial equation of state, except that it is more accurate at high-density states, while the virial equation has the low-density limitation. Both equations contain the common set of the so-called irreducible integrals, related to the corresponding virial coefficients, and can be used together to describe the behavior of a lattice gas in a wide range of densities.
Towards the simplest hydrodynamic lattice-gas model.
Boghosian, Bruce M; Love, Peter J; Meyer, David A
2002-03-15
It has been known since 1986 that it is possible to construct simple lattice-gas cellular automata whose hydrodynamics are governed by the Navier-Stokes equations in two dimensions. The simplest such model heretofore known has six bits of state per site on a triangular lattice. In this work, we demonstrate that it is possible to construct a model with only five bits of state per site on a Kagome lattice. Moreover, the model has a simple, deterministic set of collision rules and is easily implemented on a computer. In this work, we derive the equilibrium distribution function for this lattice-gas automaton and carry out the Chapman-Enskog analysis to determine the form of the Navier-Stokes equations.
Spontaneous formation of large clusters in a lattice gas above the critical point.
Khain, Evgeniy; Khasin, Michael; Sander, Leonard M
2014-12-01
We consider clustering of particles in the lattice gas model above the critical point. We find the probability for large density fluctuations over scales much larger than the correlation length. This fundamental problem is of interest in various biological contexts such as quorum sensing and clustering of motile, adhesive, cancer cells. In the latter case, it may give a clue to the problem of growth of recurrent tumors. We develop a formalism for the analysis of this rare event employing a phenomenological master equation and measuring the transition rates in numerical simulations. The spontaneous clustering is treated in the framework of the eikonal approximation to the master equation.
Lattice-gas models of phase separation: interfaces, phase transitions, and multiphase flow
Rothman, D.H. ); Zaleski, S. )
1994-10-01
Momentum-conserving lattice gases are simple, discrete, microscopic models of fluids. This review describes their hydrodynamics, with particular attention given to the derivation of macroscopic constitutive equations from microscopic dynamics. Lattice-gas models of phase separation receive special emphasis. The current understanding of phase transitions in these momentum-conserving models is reviewed; included in this discussion is a summary of the dynamical properties of interfaces. Because the phase-separation models are microscopically time irreversible, interesting questions are raised about their relationship to real fluid mixtures. Simulation of certain complex-fluid problems, such as multiphase flow through porous media and the interaction of phase transitions with hydrodynamics, is illustrated.
Spontaneous formation of large clusters in a lattice gas above the critical point
NASA Astrophysics Data System (ADS)
Khain, Evgeniy; Khasin, Michael; Sander, Leonard M.
2014-12-01
We consider clustering of particles in the lattice gas model above the critical point. We find the probability for large density fluctuations over scales much larger than the correlation length. This fundamental problem is of interest in various biological contexts such as quorum sensing and clustering of motile, adhesive, cancer cells. In the latter case, it may give a clue to the problem of growth of recurrent tumors. We develop a formalism for the analysis of this rare event employing a phenomenological master equation and measuring the transition rates in numerical simulations. The spontaneous clustering is treated in the framework of the eikonal approximation to the master equation.
An Efficient and Accurate Quantum Lattice-Gas Model for the Many-Body Schroedinger Wave Equation
2002-01-01
CONTRACT NUMBER AN EFFICIENT AND ACCURATE QUANTUM LATTICE-GAS MODEL FOR THE MANY-BODY SCHROEDINGER WAVE EQUATION 5b. GRANT NUMBER SC. PROGRAM ELEMENT...for simulating the time-dependent evolution of a many-body jiiantum mechanical system of particles governed by the non-relativistic Schroedinger " wave...the numerical dispersion of the simulated wave packets is compared with the analytical solutions. 15. SUBJECT TERM: Schroedinger wave equation
Lattice gas automata for flow and transport in geochemical systems
Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.
1992-05-01
Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.
A lattice gas of prime numbers and the Riemann Hypothesis
NASA Astrophysics Data System (ADS)
Vericat, Fernando
2013-10-01
In recent years, there has been some interest in applying ideas and methods taken from Physics in order to approach several challenging mathematical problems, particularly the Riemann Hypothesis. Most of these kinds of contributions are suggested by some quantum statistical physics problems or by questions originated in chaos theory. In this article, we show that the real part of the non-trivial zeros of the Riemann zeta function extremizes the grand potential corresponding to a simple model of one-dimensional classical lattice gas, the critical point being located at 1/2 as the Riemann Hypothesis claims.
Lattice gas automata for flow and transport in geochemical systems
Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.
1992-01-01
Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.
Critical dynamics of the jamming transition in one-dimensional nonequilibrium lattice-gas models.
Priyanka; Jain, Kavita
2016-04-01
We consider several one-dimensional driven lattice-gas models that show a phase transition in the stationary state between a high-density fluid phase in which the typical length of a hole cluster is of order unity and a low-density jammed phase where a hole cluster of macroscopic length forms in front of a particle. Using a hydrodynamic equation for an interface growth model obtained from the driven lattice-gas models of interest here, we find that in the fluid phase, the roughness exponent and the dynamic exponent that, respectively, characterize the scaling of the saturation width and the relaxation time of the interface with the system size are given by the Kardar-Parisi-Zhang exponents. However, at the critical point, we show analytically that when the equal-time density-density correlation function decays slower than inverse distance, the roughness exponent varies continuously with a parameter in the hop rates, but it is one-half otherwise. Using these results and numerical simulations for the density-density autocorrelation function, we further find that the dynamic exponent z=3/2 in all cases.
Thermodynamics of a lattice gas with linear attractive potential
Pirjol, Dan; Schat, Carlos
2015-01-15
We study the equilibrium thermodynamics of a one-dimensional lattice gas with interaction V(|i−j|)=−1/(μn) (ξ−1/n |i−j|) given by the superposition of a universal attractive interaction with strength −1/(μn) ξ<0, and a linear attractive potential 1/(μn{sup 2}) |i−j|. The interaction is rescaled with the lattice size n, such that the thermodynamical limit n → ∞ is well-behaved. The thermodynamical properties of the system can be found exactly, both for a finite size lattice and in the thermodynamical limit n → ∞. The lattice gas can be mapped to a system of non-interacting bosons which are placed on known energy levels. The exact solution shows that the system has a liquid-gas phase transition for ξ > 0. In the large temperature limit T ≫ T{sub 0}(ρ) = ρ{sup 2}/(4μ) with ρ the density, the system becomes spatially homogeneous, and the equation of state is given to a good approximation by a lattice version of the van der Waals equation, with critical temperature T{sub c}{sup (vdW)}=1/(12μ) (3ξ−1)
Nucleation near the eutectic point in a Potts-lattice gas model.
Agarwal, Vishal; Peters, Baron
2014-02-28
We use the Potts-lattice gas model to study nucleation at and near the eutectic composition. We use rare-event methods to compute the free energy landscape for the competing nucleation products, and short trajectories at the barrier top to obtain prefactors. We introduce a procedure to tune the frequency of semigrand Monte Carlo moves so that the dynamics of a small closed system roughly resemble those of an infinite system. The non-dimensionalized nucleation rates follow trends as predicted by the classical nucleation theory. Finally, we develop corrections that convert free energy surfaces from closed (canonical) simulations into free energy surfaces from open (semigrand) simulations. The new corrections extend earlier corrections to now address situations like nucleation at the eutectic point where two products nucleate competitively.
Measurement-Induced Localization of an Ultracold Lattice Gas
NASA Astrophysics Data System (ADS)
Patil, Y. S.; Chakram, S.; Vengalattore, M.
2015-10-01
The process of measurement can modify the state of a quantum system and its subsequent evolution. Here, we demonstrate the control of quantum tunneling in an ultracold lattice gas by the measurement backaction imposed by the act of imaging the atoms, i.e., light scattering. By varying the rate of light scattering from the atomic ensemble, we show the crossover from the weak measurement regime, where position measurements have little influence on tunneling dynamics, to the strong measurement regime, where measurement-induced localization causes a large suppression of tunneling—a manifestation of the quantum Zeno effect. Our study realizes an experimental demonstration of the paradigmatic Heisenberg microscope and sheds light on the implications of measurement on the coherent evolution of a quantum system.
History dependent quantum random walks as quantum lattice gas automata
Shakeel, Asif E-mail: dmeyer@math.ucsd.edu Love, Peter J. E-mail: dmeyer@math.ucsd.edu; Meyer, David A. E-mail: dmeyer@math.ucsd.edu
2014-12-15
Quantum Random Walks (QRW) were first defined as one-particle sectors of Quantum Lattice Gas Automata (QLGA). Recently, they have been generalized to include history dependence, either on previous coin (internal, i.e., spin or velocity) states or on previous position states. These models have the goal of studying the transition to classicality, or more generally, changes in the performance of quantum walks in algorithmic applications. We show that several history dependent QRW can be identified as one-particle sectors of QLGA. This provides a unifying conceptual framework for these models in which the extra degrees of freedom required to store the history information arise naturally as geometrical degrees of freedom on the lattice.
Microscopic reversibility and macroscopic irreversibility: A lattice gas model
NASA Astrophysics Data System (ADS)
Pérez-Cárdenas, Fernando C.; Resca, Lorenzo; Pegg, Ian L.
2016-09-01
We present coarse-grained descriptions and computations of the time evolution of a lattice gas system of indistinguishable particles, whose microscopic laws of motion are exactly reversible, in order to investigate how or what kind of macroscopically irreversible behavior may eventually arise. With increasing coarse-graining and number of particles, relative fluctuations of entropy rapidly decrease and apparently irreversible behavior unfolds. Although that behavior becomes typical in those limits and within a certain range, it is never absolutely irreversible for any individual system with specific initial conditions. Irreversible behavior may arise in various ways. We illustrate one possibility by replacing detailed integer occupation numbers at lattice sites with particle probability densities that evolve diffusively.
Imaginary time integration method using a quantum lattice gas approach
NASA Astrophysics Data System (ADS)
Oganesov, Armen; Flint, Christopher; Vahala, George; Vahala, Linda; Yepez, Jeffrey; Soe, Min
2016-02-01
By modifying the collision operator in the quantum lattice gas (QLG) algorithm one can develop an imaginary time (IT) integration to determine the ground state solutions of the Schrödinger equation and its variants. These solutions are compared to those found by other methods (in particular the backward-Euler finite-difference scheme and the quantum lattice Boltzmann). In particular, the ground state of the quantum harmonic oscillator is considered as well as bright solitons in the one-dimensional (1D) non-linear Schrödinger equation. The dark solitons in an external potential are then determined. An advantage of the QLG IT algorithm is the avoidance of any real/complex matrix inversion and that its extension to arbitrary dimensions is straightforward.
Dynamical Behavior of Multi-Robot Systems Using Lattice Gas Automata
Cameron, S.M.; Robinett, R.; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.
1999-03-11
Recent attention has been given to the deployment of an adaptable sensor array realized by multi-robotic systems. Our group has been studying the collective behavior of autonomous, multi-agent systems and their applications in the area of remote-sensing and emerging threats. To accomplish such tasks, an interdisciplinary research effort at Sandia National Laboratories are conducting tests in the fields of sensor technology, robotics, and multi-robotic and multi-agents architectures. Our goal is to coordinate a constellation of point sensors that optimizes spatial coverage and multivariate signal analysis using unmanned robotic vehicles (e.g., RATLERs, Robotic All-ten-sin Lunar Exploration Rover-class vehicles). Overall design methodology is to evolve complex collective behaviors realized through simple interaction (kinetic) physics and artificial intelligence to enable real-time operational responses to emerging threats. This paper focuses on our recent work understanding the dynamics of many-body systems using the physics-based hydrodynamic model of lattice gas automata. Three design features are investigated. One, for single-speed robots, a hexagonal nearest-neighbor interaction topology is necessary to preserve standard hydrodynamic flow. Two, adaptability, defined by the swarm's deformation rate, can be controlled through the hydrodynamic viscosity term, which, in turn, is defined by the local robotic interaction rules. Three, due to the inherent non-linearity of the dynamical equations describing large ensembles, development of stability criteria ensuring convergence to equilibrium states is developed by scaling information flow rates relative to a swarm's hydrodynamic flow rate. An initial test case simulates a swarm of twenty-five robots that maneuvers past an obstacle while following a moving target. A genetic algorithm optimizes applied nearest-neighbor forces in each of five spatial regions distributed over the simulation domain. Armed with knowledge, the
Catalytic formation of ammonia: a lattice gas non-thermal Langmuir Hinshelwood mechanism
NASA Astrophysics Data System (ADS)
Khan, K. M.; Ahmad, N.; Albano, E. V.
2001-11-01
The catalytic formation of ammonia synthesis through dimers N 2 and H 2 has been studied through Monte-Carlo simulation via a model based on lattice gas non-thermal Langmuir-Hinshelwood mechanism, which involves the precursor motion of H 2 molecule. The most interesting feature of this model is it yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The phase diagram is qualitatively similar to well-known ZGB model. The width of the window depends upon the mobility of precursors. The continuous transition disappears when mobility of precursors is extended to third nearest neighbourhood. The dependence of production rate on partial pressure of hydrogen is predicted by simple mathematical equations in our model. Some more interesting results are observed when reaction between precursors and chemisorbed hydrogen atoms is considered.
Two-dimensional crystals of Rydberg excitations in a resonantly driven lattice gas
NASA Astrophysics Data System (ADS)
Petrosyan, David
2013-10-01
The competition between resonant optical excitation of Rydberg states of atoms and their strong, long-range van der Waals interaction results in spatial ordering of Rydberg excitations in a two-dimensional lattice gas, as observed in a recent experiment of Schauß [Nature (London)NATUAS0028-083610.1038/nature11596 491, 87 (2012)]. Here we use semiclassical Monte Carlo simulations to obtain stationary states for hundreds of atoms in finite-size lattices. We show the formation of regular spatial structures of Rydberg excitations in a system of increasing size, and find highly sub-Poissonian distribution of the number of Rydberg excitations characterized by a large negative value of the Mandel Q parameter which is nearly independent of the system size.
Crackling sound generation during the formation of liquid bridges: A lattice gas model
NASA Astrophysics Data System (ADS)
Almeida, Alexandre B.; Buldyrev, Sergey V.; Alencar, Adriano M.
2013-08-01
Due to abnormal mechanical instabilities, liquid bridges may form in the small airways blocking airflow. Liquid bridge ruptures during inhalation are the major cause of the crackling adventitious lung sound, which can be heard using a simple stethoscope. Recently, Vyshedskiy and colleagues (2009) [1] described and characterized a crackle sound originated during expiration. However, the mechanism and origin of the expiratory crackle are still controversial. Thus, in this paper, we propose a mechanism for expiratory crackles. We hypothesize that the expiratory crackle sound is a result of the energy released in the form of acoustic waves during the formation of the liquid bridge. The magnitude of the energy released is proportional to the difference in free energy prior and after the bridge formation. We use a lattice gas model to describe the liquid bridge formation between two parallel planes. Specifically, we determine the surface free energy and the conditions of the liquid bridge formation between two parallel planes separated by a distance 2h by a liquid droplet of volume Ω and contact angle Θ, using both Monte Carlo simulation of a lattice gas model and variational calculus based on minimization of the surface area with the volume and the contact angle constrained. We numerically and analytically determine the phase diagram of the system as a function of the dimensionless parameter hΩ and Θ. We can distinguish two different phases: one droplet and one liquid bridge. We observe a hysteresis curve for the energy changes between these two states, and a finite size effect in the bridge formation. We compute the release of free energy during the formation of the liquid bridge and discuss the results in terms of system size. We also calculate the force exerted from liquid bridge on the planes by studying the dependence of the free energy on the separation between the planes 2h. The simulation results are in agreement with the analytical solution.
NASA Astrophysics Data System (ADS)
Rubio Puzzo, M. Leticia; Saracco, Gustavo P.; Bab, Marisa A.
2016-02-01
Phase transitions and damage spreading for a lattice gas model with mixed driven lattice gas (DLG)-Glauber dynamics are studied by means of Monte Carlo simulations. In order to control the number of sites updated according to the nonconservative Glauber dynamics, a parameter pɛ [ 0 , 1 ] is defined. In this way, for p = 0 the system corresponds to the DLG model with biased Kawasaki conservative dynamics, while for p = 1 it corresponds to the Ising model with Glauber dynamics. The results obtained show that the introduction of nonconservative dynamics dramatically affects the behavior of the DLG model, leading to the existence of Ising-like phase transitions from fully occupied to disordered states. The short-time dynamics results suggest that this transition is second order for values of p = 0.1 and p > 0.6 and first order for 0.1 < p ≤ 0.6. On the other hand, damage always spreads within the investigated temperature range and reaches a saturation value Dsat that depends on the system size, the temperature, and p. The value of Dsat in the thermodynamic limit is estimated by performing a finite-size analysis. For p < 0.6 the results show a change in the behavior of Dsat with temperature, similar to those reported for the pure (p = 0) DLG model. However, for p ≥ 0.6 the data remind us of the Ising (p = 1) curves. In each case, a damage temperature TD(p) can be defined as the value where either Dsat reaches a maximum or it becomes nonzero. This temperature is, within error bars, similar to the reported values of the temperatures that characterize the mentioned phase transitions.
Nucleation in a Potts lattice gas model of crystallization from solution
NASA Astrophysics Data System (ADS)
Duff, Nathan; Peters, Baron
2009-11-01
Nucleation from solution is important in many pharmaceutical crystallization, biomineralization, material synthesis, and self-assembly processes. Simulation methodology has progressed rapidly for studies of nucleation in pure component and implicit solvent systems; however little progress has been made in the simulation of explicit solvent systems. The impasse stems from the inability of rare events simulation methodology to be combined with simulation techniques which maintain a constant chemical potential driving force (supersaturation) for nucleation. We present a Potts lattice gas (PLG) to aid in the development of new simulation strategies for nucleation from solution. The PLG captures common crystallization phase diagram features such as a eutectic point and solute/solvent melting points. Simulations of the PLG below the bulk solute melting temperature reveal a competition between amorphous and crystalline nuclei. As the temperature is increased toward the bulk melting temperature, the nucleation pathway changes from a one step crystalline nucleation pathway to a two step pathway, where an amorphous nucleus forms and then crystallizes. We explain these results in terms of classical nucleation theory with different size-dependant chemical potentials for the amorphous and crystalline nucleation pathways. The two step pathway may be particularly important when crystallization is favored only at postcritical sizes.
Nucleation in a Potts lattice gas model of crystallization from solution.
Duff, Nathan; Peters, Baron
2009-11-14
Nucleation from solution is important in many pharmaceutical crystallization, biomineralization, material synthesis, and self-assembly processes. Simulation methodology has progressed rapidly for studies of nucleation in pure component and implicit solvent systems; however little progress has been made in the simulation of explicit solvent systems. The impasse stems from the inability of rare events simulation methodology to be combined with simulation techniques which maintain a constant chemical potential driving force (supersaturation) for nucleation. We present a Potts lattice gas (PLG) to aid in the development of new simulation strategies for nucleation from solution. The PLG captures common crystallization phase diagram features such as a eutectic point and solute/solvent melting points. Simulations of the PLG below the bulk solute melting temperature reveal a competition between amorphous and crystalline nuclei. As the temperature is increased toward the bulk melting temperature, the nucleation pathway changes from a one step crystalline nucleation pathway to a two step pathway, where an amorphous nucleus forms and then crystallizes. We explain these results in terms of classical nucleation theory with different size-dependant chemical potentials for the amorphous and crystalline nucleation pathways. The two step pathway may be particularly important when crystallization is favored only at postcritical sizes.
Enantiomeric phase separation in a lattice gas model: Guggenheim approximation
NASA Astrophysics Data System (ADS)
Huckaby, Dale A.; Shinmi, Masato; Ausloos, Marcel; Clippe, Paulette
1986-05-01
We consider a lattice gas in which the two enantiomeric forms of a tetrahedral molecule, consisting of a central carbon atom bonded to four different groups A, B, G, and H, are adsorbed onto a triangular lattice, such that the carbon atom is above a lattice site, the three bonds to A, B, and G point toward neighboring lattice sites, and the bond to H points perpendicular to and away from the plane of the lattice. For a certain choice of intermolecular interactions, such as may exist between the zwitterion forms of an amino acid, the phase diagram was investigated using a Guggenheim approximation with two order parameters. Enantiomeric phase separation into two symmetric condensed phases occurs at low temperatures. These condensed phases become a single racemic condensed phase at a critical line, and they are in equilibrium with a racemic gas phase along a line of triple points. These two lines coincide at a critical endpoint. The racemic condensed and gas phases are in equilibrium along a two phase coexistence line which begins at the critical endpoint and ends at a critical point. No tricritical point was found in the model for the special choice of interactions studied.
Solution of an associating lattice-gas model with density anomaly on a Husimi lattice.
Oliveira, Tiago J; Stilck, Jürgen F; Barbosa, Marco Aurélio A
2010-11-01
We study a model of a lattice gas with orientational degrees of freedom which resemble the formation of hydrogen bonds between the molecules. In this model, which is the simplified version of the Henriques-Barbosa model, no distinction is made between donors and acceptors in the bonding arms. We solve the model in the grand-canonical ensemble on a Husimi lattice built with hexagonal plaquettes with a central site. The ground state of the model, which was originally defined on the triangular lattice, is exactly reproduced by the solution on this Husimi lattice. In the phase diagram, one gas and two liquid [high density liquid (HDL) and low density liquid (LDL)] phases are present. All phase transitions (GAS-LDL, GAS-HDL, and LDL-HDL) are discontinuous, and the three phases coexist at a triple point. A line of temperatures of maximum density in the isobars is found in the metastable GAS phase, as well as another line of temperatures of minimum density appears in the LDL phase, part of it in the stable region and another in the metastable region of this phase. These findings are at variance with simulational results for the same model on the triangular lattice, which suggested a phase diagram with two critical points. However, our results show very good quantitative agreement with the simulations, both for the coexistence loci and the densities of particles and of hydrogen bonds. We discuss the comparison of the simulations with our results.
Solution of an associating lattice-gas model with density anomaly on a Husimi lattice
NASA Astrophysics Data System (ADS)
Oliveira, Tiago J.; Stilck, Jürgen F.; Barbosa, Marco Aurélio A.
2010-11-01
We study a model of a lattice gas with orientational degrees of freedom which resemble the formation of hydrogen bonds between the molecules. In this model, which is the simplified version of the Henriques-Barbosa model, no distinction is made between donors and acceptors in the bonding arms. We solve the model in the grand-canonical ensemble on a Husimi lattice built with hexagonal plaquettes with a central site. The ground state of the model, which was originally defined on the triangular lattice, is exactly reproduced by the solution on this Husimi lattice. In the phase diagram, one gas and two liquid [high density liquid (HDL) and low density liquid (LDL)] phases are present. All phase transitions (GAS-LDL, GAS-HDL, and LDL-HDL) are discontinuous, and the three phases coexist at a triple point. A line of temperatures of maximum density in the isobars is found in the metastable GAS phase, as well as another line of temperatures of minimum density appears in the LDL phase, part of it in the stable region and another in the metastable region of this phase. These findings are at variance with simulational results for the same model on the triangular lattice, which suggested a phase diagram with two critical points. However, our results show very good quantitative agreement with the simulations, both for the coexistence loci and the densities of particles and of hydrogen bonds. We discuss the comparison of the simulations with our results.
Lattice gas cellular automation model for rippling and aggregation in myxobacteria
NASA Astrophysics Data System (ADS)
Alber, Mark S.; Jiang, Yi; Kiskowski, Maria A.
2004-05-01
A lattice gas cellular automation (LGCA) model is used to simulate rippling and aggregation in myxobacteria. An efficient way of representing cells of different cell size, shape and orientation is presented that may be easily extended to model later stages of fruiting body formation. This LGCA model is designed to investigate whether a refractory period, a minimum response time, a maximum oscillation period and non-linear dependence of reversals of cells on C-factor are necessary assumptions for rippling. It is shown that a refractory period of 2-3 min, a minimum response time of up to 1 min and no maximum oscillation period best reproduce rippling in the experiments of Myxococcus xanthus. Non-linear dependence of reversals on C-factor is critical at high cell density. Quantitative simulations demonstrate that the increase in wavelength of ripples when a culture is diluted with non-signaling cells can be explained entirely by the decreased density of C-signaling cells. This result further supports the hypothesis that levels of C-signaling quantitatively depend on and modulate cell density. Analysis of the interpenetrating high density waves shows the presence of a phase shift analogous to the phase shift of interpenetrating solitons. Finally, a model for swarming, aggregation and early fruiting body formation is presented.
Laterally driven interfaces in the three-dimensional Ising lattice gas.
Smith, Thomas H R; Vasilyev, Oleg; Maciołek, Anna; Schmidt, Matthias
2010-08-01
We study the steady state of a phase-separated driven Ising lattice gas in three dimensions using computer simulations with Kawasaki dynamics. An external force field F(z) acts in the x direction parallel to the interface, creating a lateral order parameter current j^{x}(z) which varies with distance z from the interface. Above the roughening temperature, our data for "shearlike" linear variation of F(z) are in agreement with the picture wherein shear acts as effective confinement in this system, thus suppressing the interfacial capillary-wave fluctuations. We find sharper magnetization profiles and reduced interfacial width as compared to equilibrium. Pair correlations are more suppressed in the vorticity direction y than in the driving direction; the opposite holds for the structure factor. Lateral transport of capillary waves occurs for those forms of F(z) for which the current j^{x}(z) is an odd function of z , for example the shearlike drive, and a "steplike" driving field. For a V-shaped driving force no such motion occurs, but capillary waves are suppressed more strongly than for the shearlike drive. These findings are in agreement with our previous simulation studies in two dimensions. Near and below the (equilibrium) roughening temperature the effective-confinement picture ceases to work, but the lateral motion of the interface persists.
Multiple phase transitions in extended hard-core lattice gas models in two dimensions.
Nath, Trisha; Rajesh, R
2014-07-01
We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition.
When is a quantum cellular automaton (QCA) a quantum lattice gas automaton (QLGA)?
NASA Astrophysics Data System (ADS)
Shakeel, Asif; Love, Peter J.
2013-09-01
Quantum cellular automata (QCA) are models of quantum computation of particular interest from the point of view of quantum simulation. Quantum lattice gas automata (QLGA - equivalently partitioned quantum cellular automata) represent an interesting subclass of QCA. QLGA have been more deeply analyzed than QCA, whereas general QCA are likely to capture a wider range of quantum behavior. Discriminating between QLGA and QCA is therefore an important question. In spite of much prior work, classifying which QCA are QLGA has remained an open problem. In the present paper we establish necessary and sufficient conditions for unbounded, finite QCA (finitely many active cells in a quiescent background) to be QLGA. We define a local condition that classifies those QCA that are QLGA, and we show that there are QCA that are not QLGA. We use a number of tools from functional analysis of separable Hilbert spaces and representation theory of associative algebras that enable us to treat QCA on finite but unbounded configurations in full detail.
Surfactant effects on droplet dynamics and deposition patterns: a lattice gas model.
Jung, Narina; Seo, Hae Won; Leo, Perry H; Kim, Jaeup; Kim, Pilwon; Yoo, Chun Sang
2017-09-12
A coarse-grained lattice gas model is developed to study pattern forming processes in drying drops containing surfactant. By performing Monte Carlo simulations of the model, the coupled dynamics of surfactant and liquid evaporation and the resulting oscillatory dynamics at the contact line are elucidated. We show that the coupled drop dynamics and the resulting final deposition patterns can be altered by adsorption kinetics. For slow adsorption rates, surfactant molecules recirculate along with colloidal particles and the area covered by the surfactant on the surface grows from the contact line as the initial concentration of the surfactant increases. This leads to coffee-ring patterns with wide rim areas upon drying or to multi-ring patterns depending on the surfactant concentration. For fast adsorption rates, a surfactant skin covers the entire surface area during the early phase of evaporation. This suppresses the coffee ring effect, and uniform patterns are obtained independent of surfactant concentration. The results suggest that the distribution of surfactant on the surface is critical in determining final deposition patterns and that understanding of the skin-forming process of the surfactant on the surface can help in manipulating the delicate pattern forming process of particles in evaporating drops.
Thermal phase transitions in a honeycomb lattice gas with three-body interactions.
Lohöfer, Maximilian; Bonnes, Lars; Wessel, Stefan
2013-11-01
We study the thermal phase transitions in a classical (hard-core) lattice gas model with nearest-neighbor three-body interactions on the honeycomb lattice, based on parallel tempering Monte Carlo simulations. This system realizes incompressible low-temperature phases at fractional fillings of 9/16, 5/8, and 3/4 that were identified in a previous study of a related quantum model. In particular, both the 9/16 and the 5/8 phase exhibit an extensive ground-state degeneracy reflecting the frustrated nature of the three-body interactions on the honeycomb lattice. The thermal melting of the 9/16 phase is found to be a first-order, discontinuous phase transition. On the other hand, from the thermodynamic behavior we obtain indications for a four-states Potts-model thermal transition out of the 5/8 phase. We find that this thermal Potts-model transition relates to the selection of one out of four extensive sectors within the low-energy manifold of the 5/8 phase, which we obtain via an exact mapping of the ground-state manifold to a hard-core dimer model on an embedded honeycomb superlattice.
Monte Carlo tests of nucleation concepts in the lattice gas model
NASA Astrophysics Data System (ADS)
Schmitz, Fabian; Virnau, Peter; Binder, Kurt
2013-05-01
The conventional theory of homogeneous and heterogeneous nucleation in a supersaturated vapor is tested by Monte Carlo simulations of the lattice gas (Ising) model with nearest-neighbor attractive interactions on the simple cubic lattice. The theory considers the nucleation process as a slow (quasistatic) cluster (droplet) growth over a free energy barrier ΔF*, constructed in terms of a balance of surface and bulk term of a critical droplet of radius R*, implying that the rates of droplet growth and shrinking essentially balance each other for droplet radius R=R*. For heterogeneous nucleation at surfaces, the barrier is reduced by a factor depending on the contact angle. Using the definition of physical clusters based on the Fortuin-Kasteleyn mapping, the time dependence of the cluster size distribution is studied for quenching experiments in the kinetic Ising model and the cluster size ℓ* where the cluster growth rate changes sign is estimated. These studies of nucleation kinetics are compared to studies where the relation between cluster size and supersaturation is estimated from equilibrium simulations of phase coexistence between droplet and vapor in the canonical ensemble. The chemical potential is estimated from a lattice version of the Widom particle insertion method. For large droplets it is shown that the physical clusters have a volume consistent with the estimates from the lever rule. Geometrical clusters (defined such that each site belonging to the cluster is occupied and has at least one occupied neighbor site) yield valid results only for temperatures less than 60% of the critical temperature, where the cluster shape is nonspherical. We show how the chemical potential can be used to numerically estimate ΔF* also for nonspherical cluster shapes.
Monte Carlo tests of nucleation concepts in the lattice gas model.
Schmitz, Fabian; Virnau, Peter; Binder, Kurt
2013-05-01
The conventional theory of homogeneous and heterogeneous nucleation in a supersaturated vapor is tested by Monte Carlo simulations of the lattice gas (Ising) model with nearest-neighbor attractive interactions on the simple cubic lattice. The theory considers the nucleation process as a slow (quasistatic) cluster (droplet) growth over a free energy barrier ΔF(*), constructed in terms of a balance of surface and bulk term of a critical droplet of radius R(*), implying that the rates of droplet growth and shrinking essentially balance each other for droplet radius R=R(*). For heterogeneous nucleation at surfaces, the barrier is reduced by a factor depending on the contact angle. Using the definition of physical clusters based on the Fortuin-Kasteleyn mapping, the time dependence of the cluster size distribution is studied for quenching experiments in the kinetic Ising model and the cluster size ℓ(*) where the cluster growth rate changes sign is estimated. These studies of nucleation kinetics are compared to studies where the relation between cluster size and supersaturation is estimated from equilibrium simulations of phase coexistence between droplet and vapor in the canonical ensemble. The chemical potential is estimated from a lattice version of the Widom particle insertion method. For large droplets it is shown that the physical clusters have a volume consistent with the estimates from the lever rule. Geometrical clusters (defined such that each site belonging to the cluster is occupied and has at least one occupied neighbor site) yield valid results only for temperatures less than 60% of the critical temperature, where the cluster shape is nonspherical. We show how the chemical potential can be used to numerically estimate ΔF(*) also for nonspherical cluster shapes.
Implementation and Performance of a Binary Lattice Gas Algorithm on Parallel Processor Systems
NASA Astrophysics Data System (ADS)
Hayot, F.; Mandal, M.; Sadayappan, P.
1989-02-01
We study the performance of a lattice gas binary algorithm on a "real arithmetic" machine, a 32 processor INTEL iPSC hypercube. The implementation is based on so-called multi-spin coding techniques. From the measured performance we extrapolate to larger and more powerful parallel systems. Comparisons are made with "bit" machines, such as the parallel Connection Machine.
Lattice gas dynamics: application to driven vortices in two dimensional superconductors.
Gotcheva, Violeta; Wang, Albert T J; Teitel, S
2004-06-18
A continuous time Monte Carlo lattice gas dynamics is developed to model driven steady states of vortices in two dimensional superconducting networks. Dramatic differences are found when compared to a simpler Metropolis dynamics. Subtle finite size effects are found at low temperature, with a moving smectic that becomes unstable to an anisotropic liquid on sufficiently large length scales.
Slow relaxation and aging kinetics for the driven lattice gas.
Daquila, George L; Täuber, Uwe C
2011-05-01
We numerically investigate the long-time behavior of the density-density autocorrelation function in driven lattice gases with particle exclusion and periodic boundary conditions in one, two, and three dimensions using precise Monte Carlo simulations. In the one-dimensional asymmetric exclusion process on a ring with half the lattice sites occupied, we find that correlations induce extremely slow relaxation to the asymptotic power law decay. We compare the crossover functions obtained from our simulations with various analytic results in the literature and analyze the characteristic oscillations that occur in finite systems away from half-filling. As expected, in three dimensions correlations are weak and consequently the mean-field description is adequate. We also investigate the relaxation toward the nonequilibrium steady state in the two-time density-density autocorrelations, starting from strongly correlated initial conditions. We obtain simple aging scaling behavior in one, two, and three dimensions, with the expected power laws.
COMMENT: Comment on 'Transverse fluctuations in the driven lattice gas'
NASA Astrophysics Data System (ADS)
Albano, Ezequiel V.
2004-08-01
Extensive simulation results of the transverse fluctuations in two driven lattice gases, the classical one with current and a modified version without current, are in agreement with the field theory proposed by Garrido et al (GSM). Based on the facts that results from both models are indistinguishable and they obey excellent scaling only by using GSM exponents, I concluded that the conclusions of the recent letter by Caracciolo et al are flawed.
Discontinuous phase transition in a dimer lattice gas
NASA Astrophysics Data System (ADS)
Dickman, Ronald
2012-05-01
I study a dimer model on the square lattice with nearest neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2, 0, 1/2} structure identified by Phares et al. [Physica B 409, 1096 (2011)] in a dimer model with finite repulsion at fixed density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q = 8 Potts model.
Discontinuous phase transition in a dimer lattice gas.
Dickman, Ronald
2012-05-07
I study a dimer model on the square lattice with nearest neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2, 0, 1/2} structure identified by Phares et al. [Physica B 409, 1096 (2011)] in a dimer model with finite repulsion at fixed density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q = 8 Potts model.
A lattice-gas model for alkali-metal fullerides: body-centred-cubic structure
NASA Astrophysics Data System (ADS)
Szabó, György; Udvardi, László
1998-05-01
A Coulomb lattice-gas model with a host-lattice screening mechanism is adapted to describe the ordering phenomena in alkali-metal fullerides of body-centred-cubic structure. It is assumed that the electric charge of an alkali ion residing at a tetrahedral interstitial site is completely screened by its first-neighbour 0953-8984/10/19/009/img5 molecules. The electronic energy of the 0953-8984/10/19/009/img6 ion is also taken into consideration as a charged spherical shell. By means of these assumptions an effective (short-range) pair interaction between two alkali ions is obtained. The resultant lattice-gas model is analysed by using two- and six-sublattice mean-field approximations. The thermodynamic properties are summarized in phase diagrams for different shell radii.
NASA Astrophysics Data System (ADS)
Georgiev, Ivan T.; McKay, Susan R.
2005-12-01
We present a general position-space renormalization-group approach for systems in steady states far from equilibrium and illustrate its application to the three-state driven lattice gas. The method is based upon the possibility of a closed form representation of the parameters controlling transition rates of the system in terms of the steady state probability distribution of small clusters, arising from the application of the master equations to small clusters. This probability distribution on various length scales is obtained through a Monte Carlo algorithm on small lattices, which then yields a mapping between parameters on different length scales. The renormalization-group flows indicate the phase diagram, analogous to equilibrium treatments. For the three-state driven lattice gas, we have implemented this procedure and compared the resulting phase diagrams with those obtained directly from simulations. Results in general show the expected topology with one exception. For high densities, an unexpected additional fixed point emerges, which can be understood qualitatively by comparing it with the fixed point of the fully asymmetric exclusion process.
NASA Astrophysics Data System (ADS)
Georgiev, Ivan T.; McKay, Susan R.
2004-03-01
We have introduced a general position-space renormalization-group approach for non-equilibrium systems developed from the microscopic master equation. The method is based upon a closed form representation of the parameters of the system in terms of the steady state probability distribution of small clusters. From the master equation in terms of these small clusters, we build recursion relations linking parameters affecting transition rates on various length scales and determine the flow topology. Results for the three-state driven lattice gas show many of the expected features associated with the phase diagrams previously reported for this system, (G. Korniss, B. Schmittmann, and R.K.P. Zia, Non-Equilibrium Phase Transitions in a Simple Three-State Lattice Gas, J. Stat. Phys. 86, 721 (1997).)in excellent agreement with simulations. The flow diagrams also exhibit added complexities, suggesting multiple regions within the ordered phase for some values of parameters and the presence of an extra "source" fixed point. (I.T. Georgiev, U. of Maine Ph.D. Thesis (2003); I.T. Georgiev and S.R. McKay, in preparation.)
Fluctuations in an ordered c (2×2) two-dimensional lattice-gas system with repulsive interactions
NASA Astrophysics Data System (ADS)
Argyrakis, P.; Chumak, A. A.; Maragakis, M.
2005-06-01
Fluctuations of the particle density in an ordered c(2×2) two-dimensional lattice-gas system are studied both analytically and by means of Monte Carlo simulations. The ordering is caused by a strong interparticle repulsive interaction resulting in the second order phase transition. The lattice of adsorption sites is divided into two sublattices (almost filled and almost empty sublattices) each of which contains a small number of structural “defects,” i.e., vacancies and excess particles. The relaxation of the correlation function of fluctuations turns out to be governed by two different functions. This peculiarity is to be contrasted with the traditional fluctuation theory which predicts the existence of a single damping constant, determined by the collective diffusion coefficient. A specific thesis of the proposed approach is that transport phenomena in ordered systems may be described in terms of both displacements and generation-recombination of structural defects. Accordingly, the correlation function of fluctuations depends on diffusion coefficients of two defect species as well as on the generation-recombination frequency. Our theory reduces to the usual one when fluctuations occur under local equilibrium conditions, i.e., for a sufficiently large size of probe areas and not too great values of interaction parameter. The analytical results agree well with those obtained in the Monte Carlo framework.
A lattice-gas model for alkali-metal fullerides: face-centred-cubic structure
NASA Astrophysics Data System (ADS)
Udvardi, László; Szabó, György
1996-12-01
A lattice-gas model is suggested for describing the ordering phenomena in alkali-metal fullerides of face-centred-cubic structure assuming that the electric charge of alkali ions residing in either octahedral or tetrahedral sites is completely screened by the first-neighbour 0953-8984/8/50/022/img5 molecules. This approximation allows us to derive an effective ion - ion interaction. The van der Waals interaction between the ion and 0953-8984/8/50/022/img5 molecule is characterized by introducing an additional site energy at the tetrahedral sites. This model is investigated by using a three-sublattice mean-field approximation and a simple cluster-variation method. The analysis shows a large variety of phase diagrams as the site energy parameter is changed.
Effect of disorder on condensation in the lattice gas model on a random graph
NASA Astrophysics Data System (ADS)
Handford, Thomas P.; Dear, Alexander; Pérez-Reche, Francisco J.; Taraskin, Sergei N.
2014-07-01
The lattice gas model of condensation in a heterogeneous pore system, represented by a random graph of cells, is studied using an exact analytical solution. A binary mixture of pore cells with different coordination numbers is shown to exhibit two phase transitions as a function of chemical potential in a certain temperature range. Heterogeneity in interaction strengths is demonstrated to reduce the critical temperature and, for large-enough degreeS of disorder, divides the cells into ones which are either on average occupied or unoccupied. Despite treating the pore space loops in a simplified manner, the random-graph model provides a good description of condensation in porous structures containing loops. This is illustrated by considering capillary condensation in a structural model of mesoporous silica SBA-15.
Competition of coarsening and shredding of clusters in a driven diffusive lattice gas
NASA Astrophysics Data System (ADS)
Kunwar, Ambarish; Chowdhury, Debashish; Schadschneider, Andreas; Nishinari, Katsuhiro
2006-06-01
We investigate a driven diffusive lattice gas model with two oppositely moving species of particle. The model is motivated by bidirectional traffic of ants on a pre-existing trail. A third species, corresponding to pheromones used by the ants for communication, is not conserved and mediates interactions between the particles. Here we study the spatio-temporal organization of the particles. In the unidirectional variant of this model it is known to be determined by the formation and coarsening of 'loose clusters'. For our bidirectional model, we show that the interaction of oppositely moving clusters is essential. In the late stages of evolution the cluster size oscillates because of a competition between their 'shredding' during encounters with oppositely moving counterparts and subsequent 'coarsening' during collision-free evolution. We also establish a nontrivial dependence of the spatio-temporal organization on the system size.
Study of the critical behavior of the driven lattice gas model with limited nonequilibrium dynamics
NASA Astrophysics Data System (ADS)
Saracco, Gustavo P.; Rubio Puzzo, M. Leticia; Bab, Marisa A.
2017-02-01
In this paper the nonequilibrium critical behavior is investigated using a variant of the well-known two-dimensional driven lattice gas (DLG) model, called modified driven lattice gas (MDLG). In this model, the application of the external field is regulated by a parameter p ɛ [ 0 , 1 ] in such a way that if p = 0, the field is not applied, and it becomes the Ising model, while if p = 1, the DLG model is recovered. The behavior of the model is investigated for several values of p by studying the dynamic evolution of the system within the short-time regime in the neighborhood of a phase transition. It is found that the system experiences second-order phase transitions in all the interval of p for the density of particles ρ = 0.5. The determined critical temperatures Tc(p) are greater than the critical temperature of the Ising model TcI, and increase with p up to the critical temperature of the DLG model in the limit of infinite driving fields. The dependence of Tc(p) on p is compatible with a power-law behavior whose exponent is ψ = 0.27(3) . Furthermore, the complete set of the critical and the anisotropic exponents is estimated. For the smallest value of p, the dynamics and β exponents are close to that calculated for the Ising model, and the anisotropic exponent Δ is near zero. As p is increased, the exponents and Δ change, meaning that the anisotropy effects increase. For the largest value investigated, the set of exponents approaches to that reported by the most recent theoretical framework developed for the DLG model.
DTIC Information for AFOSR Task 2304CP Lattice-Gas Theory and Computation for Complex Fluid Dynamics
1997-11-06
by ANSI Std Z39-18 ifested sound waves, surprising fluid-like behavior given the model’s simplicity and severe spacetime discretization. The transport...the integer lattice-gas: (1) is exactly computed on a discrete spacetime lattice (all the additive con- served quantities, e.g. mass and momentum, are
Meyer, D.A.
1995-12-01
The goal of this project has been to build on the understanding of the connections between knot invariants, exactly solvable statistical mechanics models and discrete dynamical systems gained in earlier work, toward an answer to the question of how early and robust thermodynamic behavior appears in lattice gas automata. These investigations have recently become relevant, unanticipatedly, to crucial issues in quantum computation.
Mente, Carsten; Voss-Böhme, Anja; Deutsch, Andreas
2015-04-01
Collective dynamics of migrating cell populations drive key processes in tissue formation and maintenance under normal and diseased conditions. Collective cell behavior at the tissue level is typically characterized by considering cell density patterns such as clusters and moving cell fronts. However, there are also important observables of collective dynamics related to individual cell behavior. In particular, individual cell trajectories are footprints of emergent behavior in populations of migrating cells. Lattice-gas cellular automata (LGCA) have proven successful to model and analyze collective behavior arising from interactions of migrating cells. There are well-established methods to analyze cell density patterns in LGCA models. Although LGCA dynamics are defined by cell-based rules, individual cells are not distinguished. Therefore, individual cell trajectories cannot be analyzed in LGCA so far. Here, we extend the classical LGCA framework to allow labeling and tracking of individual cells. We consider cell number conserving LGCA models of migrating cell populations where cell interactions are regulated by local cell density and derive stochastic differential equations approximating individual cell trajectories in LGCA. This result allows the prediction of complex individual cell trajectories emerging in LGCA models and is a basis for model-experiment comparisons at the individual cell level.
Guo, Xiaofang; De Decker, Y; Evans, J W
2010-08-01
We analyze metastability associated with a discontinuous nonequilibrium phase transition in a stochastic lattice-gas realization of Schloegl's second model for autocatalysis. This model realization involves spontaneous annihilation, autocatalytic creation, and diffusion of particles on a square lattice, where creation at empty sites requires an adjacent diagonal pair of particles. This model, also known as the quadratic contact process, exhibits discontinuous transition between a populated active state and a particle-free vacuum or "poisoned" state, as well as generic two-phase coexistence. The poisoned state exists for all particle annihilation rates p>0 and hop rates h≥0 and is an absorbing state in the sense of Markovian processes. The active or reactive steady state exists only for p below a critical value, p{e}=p{e}(h) , but a metastable extension appears for a range of higher p up to an effective upper spinodal point, p{s+}=p{s+}(h) (i.e., p{s+}>p{e} ). For selected h , we assess the location of p{s+}(h) by characterizing both the poisoning kinetics and the propagation of interfaces separating vacuum and active states as a function of p .
Microcanonical Monte Carlo study of one dimensional self-gravitating lattice gas models
NASA Astrophysics Data System (ADS)
Maciel, Joao Marcos; Amato, Marco Antônio; da Rocha Filho, Tarcisio Marciano; Figueiredo, Annibal D.
2017-03-01
In this study we present a microcanonical Monte Carlo investigation of one dimensional (1 - d) self-gravitating toy models. We study the effect of hard-core potentials and compare to the results obtained with softening parameters and also the effect of the topology on these systems. In order to study the effect of the topology in the system we introduce a model with the symmetry of motion in a line instead of a circle, which we denominate as 1 /r model. The hard-core particle potential introduces the effect of the size of particles and, consequently, the effect of the density of the system that is redefined in terms of the packing fraction of the system. The latter plays a role similar to the softening parameter ɛ in the softened particles' case. In the case of low packing fractions both models with hard-core particles show a behavior that keeps the intrinsic properties of the three dimensional gravitational systems such as negative heat capacity. For higher values of the packing fraction the ring model behaves as the potential for the standard cosine Hamiltonian Mean Field model while for the 1 /r model it is similar to the one-dimensional systems. In the present paper we intend to show that a further simplification level is possible by introducing the lattice-gas counterpart of such models, where a drastic simplification of the microscopic state is obtained by considering a local average of the exact N-body dynamics.
Lattice-Gas Automata for the Problem Of Kinetic Theory of Gas During Free Expansion
NASA Astrophysics Data System (ADS)
Khotimah, Siti Nurul; Arif, Idam; Liong, The Houw
The lattice-gas method has been applied to solve the problem of kinetic theory of gas in the Gay-Lussac-Joule experiment. Numerical experiments for a two-dimensional gas were carried out to determine the number of molecules in one vessel (Nr), the ratio between the mean square values of the components of molecule velocity (/line{vx2}//line{v_y^2}), and the change in internal energy (ΔU) as a function of time during free expansion. These experiments were repeated for different sizes of an aperture in the partition between the two vessels. After puncturing the partition, the curve for the particle number in one vessel shows a damped oscillation for about half of the total number. The oscillations do not vanish after a sampling over different initial configurations. The system is in nonequilibrium due to the pressure equilibration, and here the flow is actually compressible. The equilibration time (in time steps) decreases with decreased size of aperture in the partition. For very small apertures (equal or less than 9{√{3}}/{2} lattice units), the number of molecules in one vessel changes with time in a smooth way until it reaches half of the total number; their curves obey the analytical solution for quasi-static processes. The calculations on /line{vx2}//line{v_y^2} and ΔU also support the results that the equilibration time decreases with decreased size of aperture in the partition.
Lattice-gas model for active vesicle transport by molecular motors with opposite polarities
NASA Astrophysics Data System (ADS)
Muhuri, Sudipto; Pagonabarraga, Ignacio
2010-08-01
We introduce a multispecies lattice-gas model for motor protein driven collective cargo transport on cellular filaments. We use this model to describe and analyze the collective motion of interacting vesicle cargos being carried by oppositely directed molecular motors, moving on a single biofilament. Building on a totally asymmetric exclusion process to characterize the motion of the interacting cargos, we allow for mass exchange with the environment, input, and output at filament boundaries and focus on the role of interconversion rates and how they affect the directionality of the net cargo transport. We quantify the effect of the various different competing processes in terms of nonequilibrium phase diagrams. The interplay of interconversion rates, which allow for flux reversal and evaporation-deposition processes, introduces qualitatively unique features in the phase diagrams. We observe regimes of three-phase coexistence, the possibility of phase re-entrance, and a significant flexibility in how the different phase boundaries shift in response to changes in control parameters. The moving steady-state solutions of this model allows for different possibilities for the spatial distribution of cargo vesicles, ranging from homogeneous distribution of vesicles to polarized distributions, characterized by inhomogeneities or shocks. Current reversals due to internal regulation emerge naturally within the framework of this model. We believe that this minimal model will clarify the understanding of many features of collective vesicle transport, apart from serving as the basis for building more exact quantitative models for vesicle transport relevant to various in vivo situations.
Phase separation dynamics of polydisperse colloids: a mean-field lattice-gas theory.
de Castro, Pablo; Sollich, Peter
2017-08-23
New insights into phase separation in colloidal suspensions are provided via a dynamical theory based on the polydisperse lattice-gas model. The model gives a simplified description of polydisperse colloids, incorporating a hard-core repulsion combined with polydispersity in the strength of the attraction between neighbouring particles. Our mean-field equations describe the local concentration evolution for each of an arbitrary number of species, and for an arbitrary overall composition of the system. We focus on the predictions for the dynamics of colloidal gas-liquid phase separation after a quench into the coexistence region. The critical point and the relevant spinodal curves are determined analytically, with the latter depending only on three moments of the overall composition. The results for the early-time spinodal dynamics show qualitative changes as one crosses a 'quenched' spinodal that excludes fractionation and so allows only density fluctuations at fixed composition. This effect occurs for dense systems, in agreement with a conjecture by Warren that, at high density, fractionation should be generically slow because it requires inter-diffusion of particles. We verify this conclusion by showing that the observed qualitative changes disappear when direct particle-particle swaps are allowed in the dynamics. Finally, the rich behaviour beyond the spinodal regime is examined, where we find that the evaporation of gas bubbles with strongly fractionated interfaces causes long-lived composition heterogeneities in the liquid phase; we introduce a two-dimensional density histogram method that allows such effects to be easily visualized for an arbitrary number of particle species.
NASA Astrophysics Data System (ADS)
Titov, S. V.; Tovbin, Yu. K.
2016-11-01
A molecular model developed earlier for a polar fluid within the lattice gas model is supplemented by considering the vibrational motions of molecules using water as an example. A combination of point dipole and Lennard-Jones potentials from SPC parametrization is chosen as the force field model for the molecule. The main thermodynamic properties of liquid water (density, internal energy, and entropy) are studied as functions of temperature. There is qualitative agreement between the calculation results and the experimental data. Ways of refining the molecular theory are discussed.
Mente, Carsten; Prade, Ina; Brusch, Lutz; Breier, Georg; Deutsch, Andreas
2011-07-01
Lattice-gas cellular automata (LGCAs) can serve as stochastic mathematical models for collective behavior (e.g. pattern formation) emerging in populations of interacting cells. In this paper, a two-phase optimization algorithm for global parameter estimation in LGCA models is presented. In the first phase, local minima are identified through gradient-based optimization. Algorithmic differentiation is adopted to calculate the necessary gradient information. In the second phase, for global optimization of the parameter set, a multi-level single-linkage method is used. As an example, the parameter estimation algorithm is applied to a LGCA model for early in vitro angiogenic pattern formation.
NASA Astrophysics Data System (ADS)
Costanza, E. F.; Costanza, G.
2017-09-01
Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion on a cubic lattice within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to a cubic three-dimensional lattice is described in detail using a successive ;unfolding; process. This example shows some new features that possess the procedure and extensions are also suggested in order to provide some another uses of the present approach.
Edison, John R; Monson, Peter A
2014-07-14
Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.
Edison, John R.; Monson, Peter A.
2014-07-14
Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.
Transfer-matrix study of a hard-square lattice gas with two kinds of particles and density anomaly.
Oliveira, Tiago J; Stilck, Jürgen F
2015-09-01
Using transfer matrix and finite-size scaling methods, we study the thermodynamic behavior of a lattice gas with two kinds of particles on the square lattice. Only excluded volume interactions are considered, so that the model is athermal. Large particles exclude the site they occupy and its four first neighbors, while small particles exclude only their site. Two thermodynamic phases are found: a disordered phase where large particles occupy both sublattices with the same probability and an ordered phase where one of the two sublattices is preferentially occupied by them. The transition between these phases is continuous at small concentrations of the small particles and discontinuous at larger concentrations, both transitions are separated by a tricritical point. Estimates of the central charge suggest that the critical line is in the Ising universality class, while the tricritical point has tricritical Ising (Blume-Emery-Griffiths) exponents. The isobaric curves of the total density as functions of the fugacity of small or large particles display a minimum in the disordered phase.
Transfer-matrix study of a hard-square lattice gas with two kinds of particles and density anomaly
NASA Astrophysics Data System (ADS)
Oliveira, Tiago J.; Stilck, Jürgen F.
2015-09-01
Using transfer matrix and finite-size scaling methods, we study the thermodynamic behavior of a lattice gas with two kinds of particles on the square lattice. Only excluded volume interactions are considered, so that the model is athermal. Large particles exclude the site they occupy and its four first neighbors, while small particles exclude only their site. Two thermodynamic phases are found: a disordered phase where large particles occupy both sublattices with the same probability and an ordered phase where one of the two sublattices is preferentially occupied by them. The transition between these phases is continuous at small concentrations of the small particles and discontinuous at larger concentrations, both transitions are separated by a tricritical point. Estimates of the central charge suggest that the critical line is in the Ising universality class, while the tricritical point has tricritical Ising (Blume-Emery-Griffiths) exponents. The isobaric curves of the total density as functions of the fugacity of small or large particles display a minimum in the disordered phase.
Phase diagram of a bidispersed hard-rod lattice gas in two dimensions
NASA Astrophysics Data System (ADS)
Kundu, Joyjit; Stilck, Jürgen F.; Rajesh, R.
2015-12-01
We obtain, using extensive Monte Carlo simulations, virial expansion and a high-density perturbation expansion about the fully packed monodispersed phase, the phase diagram of a system of bidispersed hard rods on a square lattice. We show numerically that when the length of the longer rods is 7, two continuous transitions may exist as the density of the longer rods is increased, keeping the density of shorter rods fixed: first from a low-density isotropic phase to a nematic phase, and second from the nematic to a high-density isotropic phase. The difference between the critical densities of the two transitions decreases to zero at a critical density of the shorter rods so that the fully packed phase is disordered for any composition. When both the rod lengths are larger than 6, we observe the existence of two transitions along the fully packed line as the composition is varied. Low-density virial expansion, truncated at the second virial coefficient, reproduces features of the first transition. By developing a high-density perturbation expansion, we show that when one of the rods is long enough, there will be at least two isotropic-nematic transitions along the fully packed line as the composition is varied.
2008-04-26
intensity of one of the mixed beams at a substrate will be proportional to 1+cos f, much as in the Mach -Zehnder interferometer f23g from classical...Dürr, G. Rempe, E. G. M. van Kempen, and B. J. Verhaa, Phys. Rev. Lett. 89, 283202 s2002d. f44g T. Volz, S. Dürr, S. Ernst , A. Marte, and G. Rempe
Elton, A.B.H.
1990-09-24
A numerical theory for the massively parallel lattice gas and lattice Boltzmann methods for computing solutions to nonlinear advective-diffusive systems is introduced. The convergence theory is based on consistency and stability arguments that are supported by the discrete Chapman-Enskog expansion (for consistency) and conditions of monotonicity (in establishing stability). The theory is applied to four lattice methods: Two of the methods are for some two-dimensional nonlinear diffusion equations. One of the methods is for the one-dimensional lattice method for the one-dimensional viscous Burgers equation. And one of the methods is for a two-dimensional nonlinear advection-diffusion equation. Convergence is formally proven in the L{sub 1}-norm for the first three methods, revealing that they are second-order, conservative, conditionally monotone finite difference methods. Computational results which support the theory for lattice methods are presented. In addition, a domain decomposition strategy using mesh refinement techniques is presented for lattice gas and lattice Boltzmann methods. The strategy allows concentration of computational resources on regions of high activity. Computational evidence is reported for the strategy applied to the lattice gas method for the one-dimensional viscous Burgers equation. 72 refs., 19 figs., 28 tabs.
NASA Astrophysics Data System (ADS)
Costanza, E. F.; Costanza, G.
2017-02-01
Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a hexagonal lattice which has the particular feature that need four types of dynamical variables. This example shows additional features to the general procedure and some extensions are also suggested in order to provide a wider insight in the present approach.
NASA Astrophysics Data System (ADS)
Costanza, E. F.; Costanza, G.
2016-12-01
Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a triangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.
NASA Astrophysics Data System (ADS)
Barry, J. H.; Muttalib, K. A.; Tanaka, T.
2008-01-01
We consider a two-dimensional (d=2) kagomé lattice gas model with attractive three-particle interactions around each triangular face of the kagomé lattice. Exact solutions are obtained for multiparticle correlations along the liquid and vapor branches of the coexistence curve and at criticality. The correlation solutions are also determined along the continuation of the curvilinear diameter of the coexistence region into the disordered fluid region. The method generates a linear algebraic system of correlation identities with coefficients dependent only upon the interaction parameter. Using a priori knowledge of pertinent solutions for the density and elementary triplet correlation, one finds a closed and linearly independent set of correlation identities defined upon a spatially compact nine-site cluster of the kagomé lattice. Resulting exact solution curves of the correlations are plotted and discussed as functions of the temperature and are compared with corresponding results in a traditional kagomé lattice gas having nearest-neighbor pair interactions. An example of application for the multiparticle correlations is demonstrated in cavitation theory.
Gavilán Arriazu, E M; López de Mishima, B A; Oviedo, O A; Leiva, E P M; Pinto, O A
2017-08-30
Herein, a Monte Carlo study within the canonical assembly has been applied to elucidate the lithium-ion phase transition order of a stage II lithium-graphite intercalation compound (LiC12) around the critical point. The results reveal a weakly first-order phase transition at 354.6 ± 0.5 K via measurements that follows the power laws with effective exponents. The graphite-lithium system was emulated within a lattice-gas model, comprising specific insertion sites arranged in four parallel planes with a triangular geometry. Moreover, two different types of energetic interactions were used: a Lennard-Jones potential, for particle interactions in the same plane, and a power law potential that decreased with distance, for particles in different planes. The energy per site and order parameter distribution were used to classify the order of the transition. Furthermore, the order parameters, susceptibility, and heat capacity were computed and analyzed.
2006-05-31
methods. LBE is a generalization of LGA, where single- particle distributions are encoded directly using real numbers. The simulation dynamics is driven...local cellular automaton rule (A.14) does not explicitly show any mixing of particle flow directions. That fact that (A.14) does represent collisional ... dynamics simulation , provides the researcher with complete system de- tails not obtainable by either empirical or analytical treatments. LGA as a
Azevedo, R M; Montenegro-Filho, R R; Coutinho-Filho, M D
2013-09-01
We use a lattice gas cellular automata model in the presence of random dynamic scattering sites and quenched disorder in the two-phase immiscible model with the aim of producing an interface dynamics similar to that observed in Hele-Shaw cells. The dynamics of the interface is studied as one fluid displaces the other in a clean lattice and in a lattice with quenched disorder. For the clean system, if the fluid with a lower viscosity displaces the other, we show that the model exhibits the Saffman-Taylor instability phenomenon, whose features are in very good agreement with those observed in real (viscous) fluids. In the system with quenched disorder, we obtain estimates for the growth and roughening exponents of the interface width in two cases: viscosity-matched fluids and the case of unstable interface. The first case is shown to be in the same universality class of the random deposition model with surface relaxation. Moreover, while the early-time dynamics of the interface behaves similarly, viscous fingers develop in the second case with the subsequent production of bubbles in the context of a complex dynamics. We also identify the Hurst exponent of the subdiffusive fractional Brownian motion associated with the interface, from which we derive its fractal dimension and the universality classes related to a percolation process.
NASA Astrophysics Data System (ADS)
Azevedo, R. M.; Montenegro-Filho, R. R.; Coutinho-Filho, M. D.
2013-09-01
We use a lattice gas cellular automata model in the presence of random dynamic scattering sites and quenched disorder in the two-phase immiscible model with the aim of producing an interface dynamics similar to that observed in Hele-Shaw cells. The dynamics of the interface is studied as one fluid displaces the other in a clean lattice and in a lattice with quenched disorder. For the clean system, if the fluid with a lower viscosity displaces the other, we show that the model exhibits the Saffman-Taylor instability phenomenon, whose features are in very good agreement with those observed in real (viscous) fluids. In the system with quenched disorder, we obtain estimates for the growth and roughening exponents of the interface width in two cases: viscosity-matched fluids and the case of unstable interface. The first case is shown to be in the same universality class of the random deposition model with surface relaxation. Moreover, while the early-time dynamics of the interface behaves similarly, viscous fingers develop in the second case with the subsequent production of bubbles in the context of a complex dynamics. We also identify the Hurst exponent of the subdiffusive fractional Brownian motion associated with the interface, from which we derive its fractal dimension and the universality classes related to a percolation process.
Parallel Markov chain Monte Carlo simulations
NASA Astrophysics Data System (ADS)
Ren, Ruichao; Orkoulas, G.
2007-06-01
With strict detailed balance, parallel Monte Carlo simulation through domain decomposition cannot be validated with conventional Markov chain theory, which describes an intrinsically serial stochastic process. In this work, the parallel version of Markov chain theory and its role in accelerating Monte Carlo simulations via cluster computing is explored. It is shown that sequential updating is the key to improving efficiency in parallel simulations through domain decomposition. A parallel scheme is proposed to reduce interprocessor communication or synchronization, which slows down parallel simulation with increasing number of processors. Parallel simulation results for the two-dimensional lattice gas model show substantial reduction of simulation time for systems of moderate and large size.
Parallel Markov chain Monte Carlo simulations.
Ren, Ruichao; Orkoulas, G
2007-06-07
With strict detailed balance, parallel Monte Carlo simulation through domain decomposition cannot be validated with conventional Markov chain theory, which describes an intrinsically serial stochastic process. In this work, the parallel version of Markov chain theory and its role in accelerating Monte Carlo simulations via cluster computing is explored. It is shown that sequential updating is the key to improving efficiency in parallel simulations through domain decomposition. A parallel scheme is proposed to reduce interprocessor communication or synchronization, which slows down parallel simulation with increasing number of processors. Parallel simulation results for the two-dimensional lattice gas model show substantial reduction of simulation time for systems of moderate and large size.
Corey, I.; Bergman, W.
1996-06-01
We have a developed a computer code that simulates 3-D filtration of suspended particles in fluids in realistic filter structures. This code, being the most advanced filtration simulation package developed to date, provides LLNL and DOE with new capabilities to address problems in cleaning liquid wastes, medical fluid cleaning, and recycling liquids. The code is an integrated system of commercially available and LLNL-developed software; the most critical are the computational fluid dynamics (CFD) solver and the particle transport program. For the CFD solver, we used a commercial package based on Navier-Stokes equations and a LLNL-developed package based on Boltzman-lattice gas equations. For the particle transport program, we developed a cod based on the 3-D Langevin equation of motion and the DLVO theory of electrical interactions. A number of additional supporting packages were purchased or developed to integrate the simulation tasks and to provide visualization output.
Monte Carlo simulation of liquid bridge rupture: Application to lung physiology
NASA Astrophysics Data System (ADS)
Alencar, Adriano M.; Wolfe, Elie; Buldyrev, Sergey V.
2006-08-01
In the course of certain lung diseases, the surface properties and the amount of fluids coating the airways changes and liquid bridges may form in the small airways blocking the flow of air, impairing gas exchange. During inhalation, these liquid bridges may rupture due to mechanical instability and emit a discrete sound event called pulmonary crackle, which can be heard using a simple stethoscope. We hypothesize that this sound is a result of the acoustical release of energy that had been stored in the surface of liquid bridges prior to its rupture. We develop a lattice gas model capable of describing these phenomena. As a step toward modeling this process, we address a simpler but related problem, that of a liquid bridge between two planar surfaces. This problem has been analytically solved and we use this solution as a validation of the lattice gas model of the liquid bridge rupture. Specifically, we determine the surface free energy and critical stability conditions in a system containing a liquid bridge of volume Ω formed between two parallel planes, separated by a distance 2h , with a contact angle Θ using both Monte Carlo simulation of a lattice gas model and variational calculus based on minimization of the surface area with the volume and the contact angle constraints. In order to simulate systems with different contact angles, we vary the parameters between the constitutive elements of the lattice gas. We numerically and analytically determine the phase diagram of the system as a function of the dimensionless parameters hΩ-1/3 and Θ . The regions of this phase diagram correspond to the mechanical stability and thermodynamical stability of the liquid bridge. We also determine the conditions for the symmetrical versus asymmetrical rupture of the bridge. We numerically and analytically compute the release of free energy during rupture. The simulation results are in agreement with the analytical solution. Furthermore, we discuss the results in connection
Monte Carlo simulation of liquid bridge rupture: application to lung physiology.
Alencar, Adriano M; Wolfe, Elie; Buldyrev, Sergey V
2006-08-01
In the course of certain lung diseases, the surface properties and the amount of fluids coating the airways changes and liquid bridges may form in the small airways blocking the flow of air, impairing gas exchange. During inhalation, these liquid bridges may rupture due to mechanical instability and emit a discrete sound event called pulmonary crackle, which can be heard using a simple stethoscope. We hypothesize that this sound is a result of the acoustical release of energy that had been stored in the surface of liquid bridges prior to its rupture. We develop a lattice gas model capable of describing these phenomena. As a step toward modeling this process, we address a simpler but related problem, that of a liquid bridge between two planar surfaces. This problem has been analytically solved and we use this solution as a validation of the lattice gas model of the liquid bridge rupture. Specifically, we determine the surface free energy and critical stability conditions in a system containing a liquid bridge of volume Omega formed between two parallel planes, separated by a distance 2h, with a contact angle Theta using both Monte Carlo simulation of a lattice gas model and variational calculus based on minimization of the surface area with the volume and the contact angle constraints. In order to simulate systems with different contact angles, we vary the parameters between the constitutive elements of the lattice gas. We numerically and analytically determine the phase diagram of the system as a function of the dimensionless parameters hOmega(-1/3) and Theta. The regions of this phase diagram correspond to the mechanical stability and thermodynamical stability of the liquid bridge. We also determine the conditions for the symmetrical versus asymmetrical rupture of the bridge. We numerically and analytically compute the release of free energy during rupture. The simulation results are in agreement with the analytical solution. Furthermore, we discuss the results in
Long-Range Lattice-Gas Algorithm
2007-11-02
lattice-gases, and therefore inherits exact computabil- ity on a discrete spacetime lattice. Our contribution is the use of nonlocal interactions that...gases, and therefore inherits exact computability on a discrete spacetime lattice. Our contribution is the use of nonlocal interactions that allow us to
Experimental Demonstration of Quantum Lattice Gas Computation
2003-04-01
30] M. Pravia, E. Fortunato, Y. Weinstein, M.D. Price, G. Teklemariam, R.J. Nelson, Y. Sharf , S. Somaroo, C.H. Tseng, T.F. Havel, and D.G. Cory...D.G. Cory, Progress in Magnetic Resonance 33 78 (1998) [33] T.F. Havel, Y. Sharf , L. Viola, and D.G. Cory Physics Letters A 280 282 (2001) [34] The
Coarse-graining the computations of surface reactions: Nonlinear dynamics from atomistic simulators
NASA Astrophysics Data System (ADS)
Makeev, Alexei G.; Kevrekidis, Ioannis G.
2009-06-01
We review and discuss the use of equation-free computation in extracting coarse-grained, nonlinear dynamics information from atomistic (lattice-gas) models of surface reactions. The approach is based on circumventing the explicit derivation of macroscopic equations for the system statistics (e.g., average coverage). Short bursts of appropriately initialized computational experimentation with the lattice-gas simulator are designed "on demand" and processed in the spirit of the coarse timestepper introduced in Theodoropoulos et al. (2000) (K. Theodoropoulos, Y.-H. Qian, I.G. Kevrekidis, Proc. Natl. Acad. Sci. USA 97 (2000) 9840). The information derived from these computational experiments, processed through traditional, continuum numerical methods is used to solve the macroscopic equations without ever deriving them in closed form. The approach is illustrated through two computational examples: the CO oxidation reaction, and the NO + CO/Pt(1 0 0) reaction.
NASA Technical Reports Server (NTRS)
Foster, F.; Randle, R.
1984-01-01
The application of flight simulation in regional airline training programs is discussed. Specifically, the use of simulation in cockpit resources management training (CRMT) is investigated. The availability of simulation resources is explored and the simulator disadvantages and advantages are cited. Problems with simulator specification, procurement, validation and use that have plagued the major air carriers over several decades are addressed.
Simulation research on pedestrian counter flow subconscious behavior
NASA Astrophysics Data System (ADS)
Li, Yongxing; Jia, Hongfei; Zhou, Ya-Nan; Yang, Lili
Analyzing the pedestrian subconscious behavior and walking environment in the passage, right-moving preference subconscious strength and overtaking subconscious strength are introduced into the pedestrian simulation model which is based on lattice gas model. Two pedestrian subconscious behavior simulation models, which are distinguished by whether considering pedestrian flow ratio of two directions or not, are established respectively. With the platform of MATLAB software, the simulations of pedestrian counter flow subconscious behavior are realized. The simulations indicate that compared with the pedestrian subconscious behavior simulation model without considering the pedestrian flow ratio of two directions, the model that considers the pedestrian flow ratio of two directions is better in simulating the pedestrian subconscious behavior.
Population dynamics of intraguild predation in a lattice gas system.
Wang, Yuanshi; Wu, Hong
2015-01-01
In the system of intraguild predation (IGP) we are concerned with, species that are in a predator-prey relationship, also compete for shared resources (space or food). While several models have been established to characterize IGP, mechanisms by which IG prey and IG predator can coexist in IGP systems with spatial competition, have not been shown. This paper considers an IGP model, which is derived from reactions on lattice and has a form similar to that of Lotka-Volterra equations. Dynamics of the model demonstrate properties of IGP and mechanisms by which the IGP leads to coexistence of species and occurrence of alternative states. Intermediate predation is shown to lead to persistence of the predator, while extremely big predation can lead to extinction of one/both species and extremely small predation can lead to extinction of the predator. Numerical computations confirm and extend our results. While empirical observations typically exhibit coexistence of IG predator and IG prey, theoretical analysis in this work demonstrates exact conditions under which this coexistence can occur. Copyright © 2014 Elsevier Inc. All rights reserved.
On the coarsening dynamics of a granular lattice gas.
Opsomer, E; Noirhomme, M; Ludewig, F; Vandewalle, N
2016-06-01
We investigated experimentally and theoretically the dynamics of a driven granular gas on a square lattice and discovered two characteristic regimes: Initially, given the dissipative nature of the collisions, particles move erratically through the system and start to gather on selected sites called traps. Later on, the formation of those traps leads to a strong decrease of the grain mobility and slows down dramatically the dynamics of the entire system. We realize detailed measurements linking a trap's stability to the global evolution of the system and propose a model reproducing the entire dynamics of the system. Our work emphasizes the complexity of coarsening dynamics of dilute granular systems.
Nonequilibrium quantum magnetism in a dipolar lattice gas.
de Paz, A; Sharma, A; Chotia, A; Maréchal, E; Huckans, J H; Pedri, P; Santos, L; Gorceix, O; Vernac, L; Laburthe-Tolra, B
2013-11-01
We report on the realization of quantum magnetism using a degenerate dipolar gas in an optical lattice. Our system implements a lattice model resembling the celebrated t-J model. It is characterized by a nonequilibrium spinor dynamics resulting from intersite Heisenberg-like spin-spin interactions provided by nonlocal dipole-dipole interactions. Moreover, due to its large spin, our chromium lattice gases constitute an excellent environment for the study of quantum magnetism of high-spin systems, as illustrated by the complex spin dynamics observed for doubly occupied sites.
Surface-subsurface model for a dimer-dimer catalytic reaction: a Monte Carlo simulation study
NASA Astrophysics Data System (ADS)
Khan, K. M.; Albano, E. V.
2002-02-01
The surface-subsurface model for a dimer-dimer reaction of the type A2 + 2B2→2AB2 has been studied through Monte Carlo simulation via a model based on the lattice gas non-thermal Langmuir-Hinshelwood mechanism, which involves the precursor motion of the B2 molecule. The motion of precursors is considered on the surface as well as in the subsurface. The most interesting feature of this model is that it yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The phase diagram is qualitatively similar to the well known Ziff, Gulari and Barshad (ZGB) model. The width of the window depends upon the mobility of precursors. The continuous transition disappears when the mobility of the surface precursors is extended to the third-nearest neighbourhood. The dependence of production rate on partial pressure of B2 dimer is predicted by simple mathematical equations in our model.
Evans, J. W.; Thiel, P. A.; Li, Maozhi
2007-06-14
We consider homoepitaxy (or low-misfit heteroepitaxy) via vapor deposition or MBE under UHV conditions. Thin film growth is initiated by nucleation and growth of 2D islands in the submonolayer regime. For atoms subsequently deposited on top of islands, a step edge barrier often inhibits downward transport and produces kinetic roughening during multilayer growth. Such unstable growth is characterized by the formation of 3D mounds (multilayer stacks of 2D islands). Kinetic Monte Carlo (KMC) simulation of suitable atomistic lattice-gas models can address fundamental or general issues related to both submonolayer and multilayer film evolution, and can also provide a predictive tool for morphological evolution in specific systems. Examples of the successes of KMC modeling are provided for metal homoepitaxial film growth, specifically for contrasting behavior in the classic Ag/Ag(100) and Ag/Ag(111) systems.
Pintus, Alberto M; Gabrieli, Andrea; Pazzona, Federico G; Demontis, Pierfranco; Suffritti, Giuseppe B
2014-08-21
We developed a coarse-grained model suitable for the study of adsorbed molecules in microporous materials. A partition of the space available to the motion of adsorbed molecules was carried out, which allows to formulate the dynamics in terms of jumps between discrete regions. The probabilities of observing given pairs of successive jumps were calculated from Molecular Dynamics (MD) simulations, performed on small systems, and used to drive the motion of molecules in a lattice-gas model. Dynamics is thus reformulated in terms of event-space dynamics and this allows to treat the system despite its inherent non markovity. Despite the assumptions enforced in the algorithm, results show that it can be applied to various spherical molecules adsorbed in the all-silica zeolite ITQ-29, establishing a suitable direct bridge between MD simulation results and coarse-grained models.
Monte Carlo simulation studies of diffusion in crowded environments
NASA Astrophysics Data System (ADS)
Nandigrami, Prithviraj; Grove, Brandy; Konya, Andrew; Selinger, Robin
Anomalous diffusion has been observed in protein solutions and other multi-component systems due to macromolecular crowding. Using Monte Carlo simulations, we investigate mechanisms that govern anomalous diffusive transport and pattern formation in a crowded mixture. We consider a multi-component lattice gas model with ``tracer'' molecules diffusing across a density gradient in a solution containing sticky ``crowder'' molecules that cluster to form dynamically evolving obstacles. The dependence of tracer flux on crowder density shows an intriguing re-entrant behavior as a function of temperature with three distinct temperature regimes. At high temperature, crowders segregate near the tracer sink but, for low enough overall crowder density, remain sufficiently disordered to allow continuous tracer flux. At intermediate temperature, crowders segregate and block tracer flux entirely, giving rise to complex pattern formation. At low temperature, crowders aggregate to form small, slowly diffusing obstacles. The resulting tracer flux shows scaling behavior near the percolation threshold, analogous to the scenario when the obstacles are fixed and randomly distributed. Our simulations predict distinct quantitative dependence of tracer flux on crowder density in these temperature limits.
Simulation estimates of cloud points of polydisperse fluids.
Buzzacchi, Matteo; Sollich, Peter; Wilding, Nigel B; Müller, Marcus
2006-04-01
We describe two distinct approaches to obtaining the cloud-point densities and coexistence properties of polydisperse fluid mixtures by Monte Carlo simulation within the grand-canonical ensemble. The first method determines the chemical potential distribution mu(sigma) (with the polydisperse attribute) under the constraint that the ensemble average of the particle density distribution rho(sigma) match a prescribed parent form. Within the region of phase coexistence (delineated by the cloud curve) this leads to a distribution of the fluctuating overall particle density n, p(n), that necessarily has unequal peak weights in order to satisfy a generalized lever rule. A theoretical analysis shows that as a consequence, finite-size corrections to estimates of coexistence properties are power laws in the system size. The second method assigns mu(sigma) such that an equal-peak-weight criterion is satisfied for p(n) for all points within the coexistence region. However, since equal volumes of the coexisting phases cannot satisfy the lever rule for the prescribed parent, their relative contributions must be weighted appropriately when determining mu(sigma). We show how to ascertain the requisite weight factor operationally. A theoretical analysis of the second method suggests that it leads to finite-size corrections to estimates of coexistence properties which are exponentially small in the system size. The scaling predictions for both methods are tested via Monte Carlo simulations of a polydisperse lattice-gas model near its cloud curve, the results showing excellent quantitative agreement with the theory.
Simulating granular media on the computer
NASA Astrophysics Data System (ADS)
Herrmann, H. J.
Granular materials, like sand or powder, can present very intriguing effects. When shaken, sheared or poured they show segregation, convection and spontaneous fluctuations in densities and stresses. I will discuss the modeling of a granular medium on a computer by simulating a packing of elastic spheres via Molecular Dynamics. Dissipation of energy and shear friction at collisions are included. In the physical range the friction coefficient is found to be a linear function of the angle of repose. On a vibrating plate the formation of convection cells due to walls or amplitude modulations can be observed. The onset of fluidization can be determined and is in good agreement with experiments. Segregation of larger particles is found to be always accompanied by convection cells. There is also ample experimental evidence showing the existence of spontaneous density patterns in granular material flowing through pipes or hoppers. The Molecular Dynamics simulations show that these density fluctuations follow a 1/f α spectrum. I compare this behavior to deterministic one-dimensional traffic models. A model with continuous positions and velocities shows self-organized critical jamming behind a slower car. The experimentally observed effects are also reproduced by Lattice Gas and Boltzmann Lattice Models. Density waves are spontaneously generated when the viscosity has a nonlinear dependence on density which characterizes granular flow. We also briefly sketch a thermodynamic formalism for loose granular material. In a dense packing non-linear acoustic phenomena, like the pressure dependence of the sound velocity are studied. Finally the plastic shear bands occurring in large scale deformations of compactified granular media are investigated using an explicit Lagrangian technique.
NASA Astrophysics Data System (ADS)
Frank, Stefan; Rikvold, Per Arne
2006-06-01
The influence of lateral adsorbate diffusion on the dynamics of the first-order phase transition in a two-dimensional Ising lattice gas with attractive nearest-neighbor interactions is investigated by means of kinetic Monte Carlo simulations. For example, electrochemical underpotential deposition proceeds by this mechanism. One major difference from adsorption in vacuum surface science is that under control of the electrode potential and in the absence of mass-transport limitations, local adsorption equilibrium is approximately established. We analyze our results using the theory of Kolmogorov, Johnson and Mehl, and Avrami (KJMA), which we extend to an exponentially decaying nucleation rate. Such a decay may occur due to a suppression of nucleation around existing clusters in the presence of lateral adsorbate diffusion. Correlation functions prove the existence of such exclusion zones. By comparison with microscopic results for the nucleation rate I and the interface velocity of the growing clusters v, we can show that the KJMA theory yields the correct order of magnitude for Iv2. This is true even though the spatial correlations mediated by diffusion are neglected. The decaying nucleation rate causes a gradual crossover from continuous to instantaneous nucleation, which is complete when the decay of the nucleation rate is very fast on the time scale of the phase transformation. Hence, instantaneous nucleation can be homogeneous, producing negative minima in the two-point correlation functions. We also present in this paper an n-fold way Monte Carlo algorithm for a square lattice gas with adsorption/desorption and lateral diffusion.
NASA Astrophysics Data System (ADS)
Lasich, Matthew; Ramjugernath, Deresh
2015-11-01
Activated carbons are popular adsorbents due to their large micro- and mesoporous volumes and high specific surface areas. Modeling adsorption behaviour using molecular computations is frequently undertaken, but the influence of the unlike intermolecular interactions on adsorption behaviour is often not well understood. This study employed grand canonical Monte Carlo simulations, and classical density functional theory coupled with a simple lattice gas model to study the influence of unlike intermolecular interactions on adsorption behaviour, with a focus on the dispersive interactions. Both approaches yielded qualitative agreement with experimental data from the literature, although only a fitted classical density functional theory approach agreed quantitatively. Changing the potential energy well depth of the methane-carbon interaction did not change the Langmuir-type adsorption behaviour observed, however, there was some dependence of the adsorption behaviour on the unlike interactions, depending on the thermodynamic conditions.
Computer simulations studies of the catalytic oxidation of carbon monoxide on platinum metals
NASA Astrophysics Data System (ADS)
Kaukonen, H.-P.; Nieminen, R. M.
1989-10-01
The steady-state catalytic oxidation process of carbon monoxide on platinum metal surfaces is studied using two irreversible kinetic computer simulation models: (a) An extended version of the model introduced by Ziff, Gulari, and Barshad (ZGB) with the effects of CO desorption and diffusion as well as finite reaction probability taken into account. The different physical processes, diffusion and desorption are studied independently and their effect on the equilibrium window, i.e., the regime where steady CO2 formation occurs is determined. (b) An interaction model where adatom-adatom nearest-neighbor (nn) interactions are taken explicitly into account through Boltzmann terms J1, J2, and J3 which are the energies of the CO-CO, O-O, and CO-O interactions, respectively. The phase diagrams in the temperature-CO-partial pressure (T,pCO-) plane are determined for different values of the nn interactions. The behavior of the system is dependent on the sign of J1(=J2 in the simulations) as well as the sign of the difference J1-J3. There is thus a clear analogy with a two-component equilibrium lattice gas with nn interactions.
NASA Astrophysics Data System (ADS)
Gavilán Arriazu, E. M.; Paz Zanini, Verónica I.; Gulotta, Florencia A.; Araujo, Virginia M.; Pinto, O. A.
2017-04-01
This paper describes the study of a redox species electrosorption on a modified electrode by experimental measurements and computer simulation. The propose model is based on the fact that charges are transferred to the electrode when an electroactive species is adsorbed on its surface. The electrode surface is modified by the irreversible adsorption of a non-electroactive species, which blocks a percentage of the adsorption sites. Hence, the electroactive species can only be adsorbed on the surface vacancies, and, when this phenomenon occurs, interact laterally with the non-electroactive one. Lattice-gas models and Monte Carlo simulations in the Gran Canonical Ensemble are used. The analysis conducted is based on the study of adsorption isotherms and voltammograms, for several values of energies and adsorption degrees of the non-electroactive species. In the case of experimental measurements, an artificial clay (Laponite®) represents the non-electroactive species while the redox probe Fe(CN)64- is the electroactive one. The results obtained by the proposed model are compared with experimental voltammograms.
Computer simulation of heterogeneous nucleation of colloidal crystals at planar walls
NASA Astrophysics Data System (ADS)
Block, B. J.; Deb, D.; Schmitz, F.; Statt, A.; Tröster, A.; Winkler, A.; Zykova-Timan, T.; Virnau, P.; Binder, K.
2014-02-01
A mini-review of the classical theory of heterogeneous nucleation at planar walls is given, and tests by Monte Carlo simulations for simple models of colloidal suspensions exhibiting a fluid-solid transition are described. This theory (due to Turnbull) assumes sphere-cap-shaped "sessile" droplets at the substrate, and the nucleation barrier that appears in the classical theory of homogeneous nucleation then is reduced by a factor depending on the Young contact angle. Various approximations inherent in this theory are examined: curvature corrections to the interfacial free energy of small droplets; neglect of anisotropy of the surface tension between crystal and fluid; neglect of corrections due to the line tension of the three-phase contact line; continuum rather than atomistic description. Also the problem of precise identification of the particles belonging (or not) to the "droplet" is discussed, and an alternative concept of extracting droplet properties from an analysis of finite size effects on phase coexistence in finite simulation boxes is explored. While the focus of our treatment is on the Asakura-Oosawa model of colloid polymer mixtures, also simple Ising/lattice gas models are considered to test some of these questions.
A simulation test of the optical Kerr mechanism for laser-induced nucleation
NASA Astrophysics Data System (ADS)
Knott, Brandon C.; Doherty, Michael F.; Peters, Baron
2011-04-01
Recent experiments have demonstrated that intense, nanosecond laser pulses can induce crystal nucleation from supersaturated solutions that are transparent at the incident wavelengths, a phenomenon termed nonphotochemical laser-induced nucleation (NPLIN). Previous work has proposed that this effect is due to the alignment of solute molecules in solution due to the electric field of the applied laser light, promoting crystalline order. We have used simulations of NPLIN to examine how an orientational bias in solution affects nucleation with Monte Carlo simulations of a Potts lattice gas model. We examine this effect within both a classical, one-step nucleation framework as well as in the context of two-step nucleation. Our results indicate that an orientational bias can reduce the free energy barrier to nucleation within the one-step picture as well as promote the crystallization of amorphous precritical nuclei (the rate-determining step in the two-step picture). However, these effects are only present with field strengths that are much greater than those used in experiments.
Rother, Gernot; Vlcek, Lukas; Gruszkiewicz, Miroslaw {Mirek} S; Chialvo, Ariel A; Anovitz, Lawrence {Larry} M; Banuelos, Jose Leo; Wallacher, Dirk; Grimm, Nico; Cole, David
2014-01-01
Adsorption of supercritical CO2 in nanoporous silica aerogel was investigated by a combination of experiments and molecular-level computer modeling. High-pressure gravimetric and vibrating tube densimetry techniques were used to measure the mean pore fluid density and excess sorption at 35 C and 50 C and pressures of 0-200 bar. Densification of the pore fluid was observed at bulk fluid densities below 0.7 g/cm3. Far above the bulk fluid density, near-zero sorption or weak depletion effects were measured, while broad excess sorption maxima form in the vicinity of the bulk critical density region. The CO2 sorption properties are very similar for two aerogels with different bulk densities of 0.1 g/cm3 and 0.2 g/cm3, respectively. The spatial distribution of the confined supercritical fluid was analyzed in terms of sorption- and bulk-phase densities by means of the Adsorbed Phase Model (APM), which used data from gravimetric sorption and small-angle neutron scattering experiments. To gain more detailed insight into supercritical fluid sorption, large-scale lattice gas GCMC simulations were utilized and tuned to resemble the experimental excess sorption data. The computed three-dimensional pore fluid density distributions show that the observed maximum of the excess sorption near the critical density originates from large density fluctuations pinned to the pore walls. At this maximum, the size of these fluctuations is comparable to the prevailing pore sizes.
Lattice-Gas Model Description of Kinetic Roughening and Fluctuations in Chemical Wave Propagation
NASA Astrophysics Data System (ADS)
Tammaro, Michael; Evans, Jim
1996-03-01
The ZGB model [1] for CO-oxidation on surfaces displays a discontinuous transition from a reactive to a CO-poisoned state, with increasing CO partial pressure. We consider the evolution of the interface between these two states in the vicinity of the poisoning transition [2]. We observe large ``intrinsic fluctuations" at the interface of the order of 10-20 lattice spacings, together with the gradual development of long-wavelength fluctuations. The latter are described by the KPZ-theory for noise-induced kinetic roughening of driven interfaces, for CO partial pressures strictly below the poisoning transition. Distinct behavior is observed and characterized right at the transition. We also show that the influence of introducing surface diffusion of adsorbed reactants into the model is to dramatically quench the intrinsic fluctuations. [1] R.M. Ziff, E. Gulari, and Y. Barshad, Phys. Rev. Lett. 56, p.2553 (1986). [2] J.W. Evans and T.R. Ray, Phys. Rev. E 50, p.4302 (1994).
Spin-Based Lattice-Gas Quantum Computers in Solids Using Optical Addressing
2007-04-30
As the length of the first pulse is increased the Rabi nutation in the echo amplitude is clearly visible. Here, only the in-phase part of the echo...4 6 10 12 14 4 1 i 20 Length of first pulse (microsec) Figure 2. Observation of Rabi nutation (single qubit rotations) using photon echo readout. (a...field is applied, the Kramer’s degenerate spin sublevels split due to the Zeeman effect. Here, the effect of an axial magnetic field (along the ion
Recovery of the Navier-Stokes equations using a lattice-gas Boltzmann method
NASA Technical Reports Server (NTRS)
Chen, Hudong; Chen, Shiyi; Matthaeus, William H.
1992-01-01
A lattice Boltzmann model is presented which gives the complete Navier-Stokes equation and may provide an efficient parallel numerical method for solving various fluid problems. The model uses the single-time relaxation approximation and a particular Maxwell-type distribution. The model eliminates exactly (1) the non-Galilean invariance caused by a density-dependent coefficient in the convection term and (2) a velocity-dependent equation of state.
Phase Diagrams of a Simple H-Bonded Lattice Gas Obtained With The Cluster Variation Method.
1981-01-01
orientation of the molecules will keep the number of cluster variables low , but it will oversimplify the entropy expression and it will of course bar us from...i.e. density approximately one half. In this model we find this state at low temperatures by adjusting the energy parameters. Such a state refers to...three parameters: e Pthe pair interaction between nearest neighbors when they are not hydrogen bonded. eH the additional pair energy between two
2012-07-01
ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NO. Air Force Research Laboratory (AFMC) AFRL/RQRC 10 E. Saturn Blvd. Edwards AFB CA 93524-7680...unlimited CRBS Results Low Intensity • Experiment and DSMC show good agreement with six-moment model (s6) for low intensity (X. Pan , “Coherent
Quantum Algorithms for Computational Physics: Volume 3 of Lattice Gas Dynamics
2007-01-03
spacetime -dependent quantity, proportional to the probability of particle occupation, the modulus squared of the wave function. The numerical solution...Chapter 4 The Dirac equation 4.1 Introduction Finding a simple rule to represent the spacetime quantum mechanical dynamics of a system of Dirac particles...Ising spin system with nearest-neighbor spin-spin interaction [Jacobson and Schulman, 1984]. The 1+1 dimensional chessboard is a square spacetime lat
Dynamic mean field theory for lattice gas models of fluid mixtures confined in mesoporous materials.
Edison, J R; Monson, P A
2013-11-12
We present the extension of dynamic mean field theory (DMFT) for fluids in porous materials (Monson, P. A. J. Chem. Phys. 2008, 128, 084701) to the case of mixtures. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable equilibrium states for fluids in pores after a change in the bulk pressure or composition. It is especially useful for studying systems where there are capillary condensation or evaporation transitions. Nucleation processes associated with these transitions are emergent features of the theory and can be visualized via the time dependence of the density distribution and composition distribution in the system. For mixtures an important component of the dynamics is relaxation of the composition distribution in the system, especially in the neighborhood of vapor-liquid interfaces. We consider two different types of mixtures, modeling hydrocarbon adsorption in carbon-like slit pores. We first present results on bulk phase equilibria of the mixtures and then the equilibrium (stable/metastable) behavior of these mixtures in a finite slit pore and an inkbottle pore. We then use DMFT to describe the evolution of the density and composition in the pore in the approach to equilibrium after changing the state of the bulk fluid via composition or pressure changes.
Recovery of the Navier-Stokes equations using a lattice-gas Boltzmann method
NASA Technical Reports Server (NTRS)
Chen, Hudong; Chen, Shiyi; Matthaeus, William H.
1992-01-01
A lattice Boltzmann model is presented which gives the complete Navier-Stokes equation and may provide an efficient parallel numerical method for solving various fluid problems. The model uses the single-time relaxation approximation and a particular Maxwell-type distribution. The model eliminates exactly (1) the non-Galilean invariance caused by a density-dependent coefficient in the convection term and (2) a velocity-dependent equation of state.
Ionic conductivity in a quantum lattice gas model with three-particle interactions
NASA Astrophysics Data System (ADS)
Barry, J. H.; Muttalib, K. A.; Tanaka, T.
2012-12-01
A system of mesoscopic ions with dominant three-particle interactions is modeled by a quantum lattice liquid on the planar kagomé lattice. The two-parameter Hamiltonian contains localized attractive triplet interactions as potential energy and nearest neighbor hopping-type terms as kinetic energy. The dynamic ionic conductivity σ(ω) is theoretically investigated for ‘weak hopping’ via a quantum many-body perturbation expansion of the thermal (Matsubara) Green function (current-current correlation). A simple analytic continuation and mapping of the thermal Green function provide the temporal Fourier transform of the physical retarded Green function in the Kubo formula. Substituting pertinent exact solutions for static multi-particle correlations known from previous work, Arrhenius relations are revealed in zeroth-order approximation for the dc ionic conductivity σdc along special trajectories in density-temperature space. The Arrhenius plots directly yield static activation energies along the latter loci. Experimental possibilities relating to σdc are discussed in the presence of equilibrium aggregation. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.
NASA Astrophysics Data System (ADS)
Ueda, Seiji; Yamada, Yoshiyuki; Kuwabara, Takashi; Gouda, Naoteru; Tsujimoto, Takuji; Kobayashi, Yukiyasu; Nakajima, Tadashi; Matsuhara, Hideo; Yano, Taihei; Suganuma, Masahiro; Jasmine Working Group
2005-04-01
We explain simulation tools in the JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Therefore it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. We find that new software technologies, such as Object Oriented (OO) methodologies, are ideal tools for the simulation system of JASMINE (the JASMINE simulator). In this article, we explain the framework of the JASMINE simulator.
ERIC Educational Resources Information Center
Stebbins, Robert C.; Allen, Brockenbrough
1975-01-01
Described are simulations that can be used to illustrate evolution by natural selection. Suggestions for simulating phenomena such as adaptive radiation, color match to background and vision of predators are offered. (BR)
NASA Astrophysics Data System (ADS)
Yamada, Yoshiyuki; Gouda, Naoteru; Yano, Taihei; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Suganuma, Masahiro; Niwa, Yoshito; Sako, Nobutada; Hatsutori, Yoichi; Tanaka, Takashi
2006-06-01
We explain simulation tools in JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations into error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented(OO) methodologies are ideal tools for the simulation system of JASMINE(the JASMINE simulator). In this article, we explain the framework of the JASMINE simulator.
Simulation of selective thermodynamic deposition in nanoholes.
Pinto, O A; López de Mishima, B A; Leiva, E P M; Oviedo, O A
2017-01-04
The deposition of particles in nanoholes is analyzed, taking into account the curvature of their inner walls. Different lattice-gas models of the nanoholes are considered. The heterogeneous surface are shaped from a (100)-surface where a nanohollow are incorporated with parallelepiped or polyhedral geometry. Several deposition stages are identified as a function of the degree of curvature of the inner walls of the nanoholes. The Monte Carlo technique in the grand canonical ensemble is used to calculate isotherms, isosteric heats, energies per site and other thermodynamic properties. This study is based on different magnitudes of the interaction energies between the particles being deposited and those surrounding the nanohole.
NASA Astrophysics Data System (ADS)
Yamada, Y.; Gouda, N.; Yano, T.; Kobayashi, Y.; Suganuma, M.; Tsujimoto, T.; Sako, N.; Hatsutori, Y.; Tanaka, T.
2006-08-01
We explain simulation tools in JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented (OO) methodologies are ideal tools for the simulation system of JASMINE (the JASMINE simulator). The simulation system should include all objects in JASMINE such as observation techniques, models of instruments and bus design, orbit, data transfer, data analysis etc. in order to resolve all issues which can be expected beforehand and make it easy to cope with some unexpected problems which might occur during the mission of JASMINE. So, the JASMINE Simulator is designed as handling events such as photons from astronomical objects, control signals for devices, disturbances for satellite attitude, by instruments such as mirrors and detectors, successively. The simulator is also applied to the technical demonstration "Nano-JASMINE". The accuracy of ordinary sensor is not enough for initial phase attitude control. Mission instruments may be a good sensor for this purpose. The problem of attitude control in initial phase is a good example of this software because the problem is closely related to both mission instruments and satellite bus systems.
NASA Technical Reports Server (NTRS)
1998-01-01
Under a NASA SBIR (Small Business Innovative Research) contract, (NAS5-30905), EAI Simulation Associates, Inc., developed a new digital simulation computer, Starlight(tm). With an architecture based on the analog model of computation, Starlight(tm) outperforms all other computers on a wide range of continuous system simulation. This system is used in a variety of applications, including aerospace, automotive, electric power and chemical reactors.
ERIC Educational Resources Information Center
Markowitz, Dina; Holt, Susan
2011-01-01
Students use manipulative models and small-scale simulations that promote learning of complex biological concepts. The authors have developed inexpensive wet-lab simulations and manipulative models for "Diagnosing Diabetes," "A Kidney Problem?" and "A Medical Mystery." (Contains 5 figures and 3 online resources.)
ERIC Educational Resources Information Center
Markowitz, Dina; Holt, Susan
2011-01-01
Students use manipulative models and small-scale simulations that promote learning of complex biological concepts. The authors have developed inexpensive wet-lab simulations and manipulative models for "Diagnosing Diabetes," "A Kidney Problem?" and "A Medical Mystery." (Contains 5 figures and 3 online resources.)
ERIC Educational Resources Information Center
Snadden, R. B.; Runquist, O.
1975-01-01
Presents an experiment in which a programmable calculator is employed as a data generating system for simulated laboratory experiments. The example used as an illustration is a simulated conductimetric titration of an aqueous solution of HC1 with an aqueous solution of NaOH. (Author/EB)
NASA Technical Reports Server (NTRS)
1993-01-01
MOOG, Inc. supplies hydraulic actuators for the Space Shuttle. When MOOG learned NASA was interested in electric actuators for possible future use, the company designed them with assistance from Marshall Space Flight Center. They also decided to pursue the system's commercial potential. This led to partnership with InterActive Simulation, Inc. for production of cabin flight simulators for museums, expositions, etc. The resulting products, the Magic Motion Simulator 30 Series, are the first electric powered simulators. Movements are computer-guided, including free fall to heighten the sense of moving through space. A projection system provides visual effects, and the 11 speakers of a digital laser based sound system add to the realism. The electric actuators are easier to install, have lower operating costs, noise, heat and staff requirements. The U.S. Space & Rocket Center and several other organizations have purchased the simulators.
NASA Astrophysics Data System (ADS)
Sinha, Indrajit; Mukherjee, Ashim K.
2014-03-01
The oxidation of CO on Pt-group metal surfaces has attracted widespread attention since a long time due to its interesting oscillatory kinetics and spatiotemporal behavior. The use of STM in conjunction with other experimental data has confirmed the validity of the surface reconstruction (SR) model under low pressure and the more recent surface oxide (SO) model which is possible under sub-atmospheric pressure conditions [1]. In the SR model the surface is periodically reconstructed below a certain low critical CO-coverage and this reconstruction is lifted above a second, higher critical CO-coverage. Alternatively the SO model proposes periodic switching between a low-reactivity metallic surface and a high-reactivity oxide surface. Here we present an overview of our recent kinetic Monte Carlo (KMC) simulation studies on the oscillatory kinetics of surface catalyzed CO oxidation. Different modifications of the lattice gas Ziff-Gulari-Barshad (ZGB) model have been utilized or proposed for this purpose. First we present the effect of desorption on the ZGB reactive to poisoned irreversible phase transition in the SR model. Next we discuss our recent research on KMC simulation of the SO model. The ZGB framework is utilized to propose a new model incorporating not only the standard Langmuir-Hinshelwood (LH) mechanism, but also introducing the Mars-van Krevelen (MvK) mechanism for the surface oxide phase [5]. Phase diagrams, which are plots between long time averages of various oscillating quantities against the normalized CO pressure, show two or three transitions depending on the CO coverage critical threshold (CT) value beyond which all adsorbed oxygen atoms are converted to surface oxide.
NASA Astrophysics Data System (ADS)
Yamada, Y.; Gouda, N.; Yano, T.; Sako, N.; Hatsutori, Y.; Tanaka, T.; Yamauchi, M.
We explain simulation tools in JASMINE project(JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented(OO) methodologies are ideal tools for the simulation system of JASMINE(the JASMINE simulator). The simulation system should include all objects in JASMINE such as observation techniques, models of instruments and bus design, orbit, data transfer, data analysis etc. in order to resolve all issues which can be expected beforehand and make it easy to cope with some unexpected problems which might occur during the mission of JASMINE. So, the JASMINE Simulator is designed as handling events such as photons from astronomical objects, control signals for devices, disturbances for satellite attitude, by instruments such as mirrors and detectors, successively. The simulator is also applied to the technical demonstration "Nano-JASMINE". The accuracy of ordinary sensor is not enough for initial phase attitude control. Mission instruments may be a good sensor for this purpose. The problem of attitude control in initial phase is a good example of this software because the problem is closely related to both mission instruments and satellite bus systems.
NASA Technical Reports Server (NTRS)
1981-01-01
Oriel Corporation's simulators have a high pressure xenon lamp whose reflected light is processed by an optical system to produce a uniform solar beam. Because of many different types of applications, the simulators must be adjustable to replicate many different areas of the solar radiation spectrum. Simulators are laboratory tools for such purposes as testing and calibrating solar cells, or other solar energy systems, testing dyes, paints and pigments, pharmaceuticals and cosmetic preparations, plant and animal studies, food and agriculture studies and oceanographic research.
Walker, Howard Andrew
2008-12-31
The Software consists of a spreadsheet written in Microsoft Excel that provides an hourly simulation of a wind energy system, which includes a calculation of wind turbine output as a power-curve fit of wind speed.
Students will use NASA Web-based simulators to follow sequenced directions and complete ordered tasks while learning how the shuttle is made ready for flight, how the shuttle docks with the Interna...
1991-05-01
to estimate the original probability of the rare event one needs to compensate for the change of measure and this involves using likelihood rations...Glynn Ward Whitt 48 12/89 A New View of the Heavy-Traffic Limit Theorem Peter W. Glynn for Many-Server Queues Ward Whitt 49 12/89 The Covariance...Validity of Sequential Stopping Rules Peter W. Glynn for Stochastic Simulations Ward Whitt 56 02/90 Analysis of Parallel, Replicated Simulations
NASA Technical Reports Server (NTRS)
Norris, Andrew
2003-01-01
The goal was to perform 3D simulation of GE90 combustor, as part of full turbofan engine simulation. Requirements of high fidelity as well as fast turn-around time require massively parallel code. National Combustion Code (NCC) was chosen for this task as supports up to 999 processors and includes state-of-the-art combustion models. Also required is ability to take inlet conditions from compressor code and give exit conditions to turbine code.
What can we hope for from cellular automata?
NASA Astrophysics Data System (ADS)
Doolen, Gary
Although the idea of using discrete methods for modeling partial differential equations occured very early, the actual statement that cellular automata techniques can approximate the solutions of hydrodynamic partial differential equations was first discovered by Frisch, Hasslacher, and Pomeau. Their description of the derivation, which assumes the validity of the Boltzmann equation, appeared in the Physical Review Letters in April 1986. It is the intent of this article to provide a description of the simplest lattice gas model and to examine the successes and inadequacies of a lattice gas calculation of flow in a two-dimensional channel. Some comments will summarize a recent result of a lattice gas simulation of flow through porous media, a problem which is ideal for the lattice gas method. Finally, some remarks will be focused on the impressive speeds which could be obtained from a dedicated lattice gas computer.
NASA Astrophysics Data System (ADS)
Goldberg, David M.; Vogeley, Michael S.
2004-04-01
We present a novel method for the simulation of the interior of large cosmic voids, suitable for the study of the formation and evolution of objects lying within such regions. Following Birkhoff's theorem, void regions dynamically evolve as universes with cosmological parameters that depend on the underdensity of the void. We derive the values of ΩM, ΩΛ, and H0 that describe this evolution. We examine how the growth rate of structure and scale factor in a void differ from the background universe. Together with a prescription for the power spectrum of fluctuations, these equations provide the initial conditions for running specialized void simulations. The increased efficiency of such simulations, in comparison to general-purpose simulations, allows an improvement of upward of 20 in the mass resolution. As a sanity check, we run a moderate-resolution simulation (N=1283 particles) and confirm that the resulting mass function of void halos is consistent with other theoretical and numerical models.
NASA Technical Reports Server (NTRS)
1996-01-01
Various NASA Small Business Innovation Research grants from Marshall Space Flight Center, Langley Research Center and Ames Research Center were used to develop the 'kernel' of COMCO's modeling and simulation software, the PHLEX finite element code. NASA needed it to model designs of flight vehicles; one of many customized commercial applications is UNISIM, a PHLEX-based code for analyzing underground flows in oil reservoirs for Texaco, Inc. COMCO's products simulate a computational mechanics problem, estimate the solution's error and produce the optimal hp-adapted mesh for the accuracy the user chooses. The system is also used as a research or training tool in universities and in mechanical design in industrial corporations.
ERIC Educational Resources Information Center
Salisbury, Howard G., III
"Simulated Agribusiness" is designed to provide the student with a role playing situation dealing with the complexities and problems of modern agriculture. It is a competitive game played on a hypothetical mid-latitude diversified farm in a capitalistic system. The player is faced with a series of decisions which will determine his success or…
NASA Astrophysics Data System (ADS)
Černý, Pavol; Henzinger, Thomas A.; Radhakrishna, Arjun
Boolean notions of correctness are formalized by preorders on systems. Quantitative measures of correctness can be formalized by real-valued distance functions between systems, where the distance between implementation and specification provides a measure of "fit" or "desirability." We extend the simulation preorder to the quantitative setting, by making each player of a simulation game pay a certain price for her choices. We use the resulting games with quantitative objectives to define three different simulation distances. The correctness distance measures how much the specification must be changed in order to be satisfied by the implementation. The coverage distance measures how much the implementation restricts the degrees of freedom offered by the specification. The robustness distance measures how much a system can deviate from the implementation description without violating the specification. We consider these distances for safety as well as liveness specifications. The distances can be computed in polynomial time for safety specifications, and for liveness specifications given by weak fairness constraints. We show that the distance functions satisfy the triangle inequality, that the distance between two systems does not increase under parallel composition with a third system, and that the distance between two systems can be bounded from above and below by distances between abstractions of the two systems. These properties suggest that our simulation distances provide an appropriate basis for a quantitative theory of discrete systems. We also demonstrate how the robustness distance can be used to measure how many transmission errors are tolerated by error correcting codes.
ERIC Educational Resources Information Center
Moertel, Cheryl; Frutiger, Bruce
1996-01-01
Describes a DNA fingerprinting simulation that uses vegetable food coloring and plastic food containers instead of DNA and expensive gel electrophoresis chambers. Allows students to decipher unknown combinations of dyes in a method similar to that used to decipher samples of DNA in DNA fingerprint techniques. (JRH)
ERIC Educational Resources Information Center
Shelly, Ann C.; Wilen, William W.
1982-01-01
Presents a simulation which can be used in any secondary social studies course to teach about the Equal Rights Amendment. It can be played with as few as ten and as many as 40 students. Playing time varies from three to seven class periods. (RM)
ERIC Educational Resources Information Center
Pipinos, Savas
2010-01-01
This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…
ERIC Educational Resources Information Center
Pipinos, Savas
2010-01-01
This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…
ERIC Educational Resources Information Center
Moertel, Cheryl; Frutiger, Bruce
1996-01-01
Describes a DNA fingerprinting simulation that uses vegetable food coloring and plastic food containers instead of DNA and expensive gel electrophoresis chambers. Allows students to decipher unknown combinations of dyes in a method similar to that used to decipher samples of DNA in DNA fingerprint techniques. (JRH)
Sanchez, J.R.; Evans, J.W.
1999-01-01
Exact results are presented for the surface diffusion of small two-dimensional clusters, the constituent atoms of which are commensurate with a square lattice of adsorption sites. Cluster motion is due to the hopping of atoms along the cluster perimeter with various rates. We apply the formalism of Titulaer and Deutch [J. Chem. Phys. {bold 77}, 472 (1982)], which describes evolution in reciprocal space via a linear master equation with dimension equal to the number of cluster configurations. We focus on the regime of rapid hopping of atoms along straight close-packed edges, where certain subsets of configurations cycle rapidly between each other. Each such subset is treated as a single quasiconfiguration, thereby reducing the dimension of the evolution equation, simplifying the analysis, and elucidating limiting behavior. We also discuss the influence of concerted atom motions on the diffusion of tetramers and larger clusters. {copyright} {ital 1999} {ital The American Physical Society}
Spatial signal amplification in cell biology: A lattice-gas model for self-tuned phase ordering
NASA Astrophysics Data System (ADS)
Ferraro, T.; de Candia, A.; Gamba, A.; Coniglio, A.
2008-09-01
Experiments show that the movement of eukaryotic cells is regulated by a process of phase separation of two competing enzymes on the cell membrane, that effectively amplifies shallow external gradients of chemical attractant. Notably, the cell is able to self-tune the final enzyme concentrations to an equilibrium state of phase coexistence, for a wide range of the average attractant concentration. We propose a simple lattice model in which, together with a short-range attraction between enzymes, a long-range repulsion naturally arises from physical considerations, that easily explains such observed behavior.
Okamoto, Atsushi; Kuwatani, Tatsu; Omori, Toshiaki; Hukushima, Koji
2015-10-01
Metastable minerals commonly form during reactions between water and rock. The nucleation mechanism of polymorphic phases from solution are explored here using a two-dimensional Potts model. The model system is composed of a solvent and three polymorphic solid phases. The local state and position of the solid phase are updated by Metropolis dynamics. Below the critical temperature, a large cluster of the least stable solid phase initially forms in the solution before transitioning into more-stable phases following the Ostwald step rule. The free-energy landscape as a function of the modal abundance of each solid phase clearly reveals that before cluster formation, the least stable phase has an energetic advantage because of its low interfacial energy with the solution, and after cluster formation, phase transformation occurs along the valley of the free-energy landscape, which contains several minima for the regions of three phases. Our results indicate that the solid-solid and solid-liquid interfacial energy contribute to the formation of the complex free-energy landscape and nucleation pathways following the Ostwald step rule.
1974-09-01
S74-28972 (20 Sept. 1974) --- Astronaut Vance D. Brand (foreground) and cosmonaut Aleksandr S. Ivanchenko are seated in the Docking Module trainer in Building 35 during Apollo-Soyuz Test Project simulation training at the Johnson Space Center. Brand is the command module pilot of the American ASTP prime crew. Ivanchenko is the engineer on the Soviet ASTP fourth crew (backup). During the exercise the American ASTP crew and the Soviet ASTP crew simulated docking the Apollo and Soyuz in Earth orbit and transferring to each other?s spacecraft. The Docking Module is designed to link the Apollo and Soyuz spacecraft. The ASTP crewmen are training in both the U.S. and USSR for the joint mission scheduled for the summer of 1975. This view is looking from inside the Command Module into the Docking Module. The hatchway loading into the Soyuz spacecraft orbital module mock-up is in the background.
NASA Astrophysics Data System (ADS)
Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.
The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.
2005-05-01
store config.) to be considered, Moving parts to be considered · Hybridisation of methods · Fast algorithms, new Aproaches · Geometry representations...Page 2 Military Aircraft Overview • Introduction • Methods ,Tools for mm-wave applications • Examples • Further requirements / developments Page 3...Flexible handling of Geometry · Parametrisation of Geometry Page 4 Military Aircraft Methods for RCS simulations •Fundamental subdivision between full
NASA Technical Reports Server (NTRS)
Fijany, Amir; Vatan, Farrokh; Barrett, Anthony; James, Mark; Mackey, Ryan; Williams, Colin
2009-01-01
The DSN Simulator (wherein DSN signifies NASA's Deep Space Network) is an updated version of the software described in DSN Array Simulator (NPO-44506), Software Tech Briefs (Special supplement to NASA Tech Briefs), Vol. 32, No. 9 (September 2008), page 26. To recapitulate: This software is used for computational modeling of proposed DSN facilities comprising arrays of antennas and transmitting and receiving equipment for microwave communication with spacecraft on interplanetary missions. Such modeling is performed to estimate facility performance, evaluate requirements that govern facility design, and evaluate proposed improvements in hardware and/or software. The software includes a Monte Carlo simulation component that enables rapid generation of key mission-set metrics (e.g., numbers of links, data rates, and data volumes), and statistical distributions thereof as functions of time. The prior version of the software could model only one DSN facility at a time and included hard-coded, unconfigurable metrics. The present updated version is capable of modeling the entire DSN and provides for configurable metrics, making it possible to perform loading analyses for alternative future DSN architectures and mission-set scenarios. The present version also features an improved user interface and interfaces for exchange of data with other DSN software and with a DSN mission model database.
NASA Technical Reports Server (NTRS)
1992-01-01
A highlight of the IMAX film, Blue Planet, is a 100-second computer- generated animation of a flight and earthquake simulation along California's San Andreas Fault. Created by the VESA group at the Jet Propulsion Laboratory, the sequence required the development of a technique to make possible terrain rendering of very large digital images. An image mosaic of California constructed from Landsat data made this possible. An advanced pyramidal terrain rendering technique was developed, significantly reducing the necessary time involved in transferring the Landsat data to film. The new technique has also enabled NASA to develop new perspective rendering technologies in order to cope with anticipated increased remote sensor data.
Trujillo, David J.; Sridharan, Srikesh; Weinstock, Irvin
2005-10-15
HybSim (short for Hybrid Simulator) is a flexible, easy to use screening tool that allows the user to quanti the technical and economic benefits of installing a village hybrid generating system and simulates systems with any combination of Diesel generator sets Photovoltaic arrays -Wind Turbines and -Battery energy storage systems Most village systems (or small population sites such as villages, remote military bases, small communities, independent or isolated buildings or centers) depend on diesel generation systems for their source of energy. HybSim allows the user to determine other "sources" of energy that can greatly reduce the dollar to kilo-watt hour ratio. Supported by the DOE, Energy Storage Program, HybSim was initially developed to help analyze the benefits of energy storage systems in Alaskan villages. Soon after its development, other sources of energy were added providing the user with a greater range of analysis opportunities and providing the village with potentially added savings. In addition to village systems, HybSim has generated interest for use from military institutions in energy provisions and USAID for international village analysis.
Edwards, Donald H.
2010-01-01
The importance of the interaction between the body and the brain for the control of behavior has been recognized in recent years with the advent of neuromechanics, a field in which the coupling between neural and biomechanical processes is an explicit focus. A major tool used in neuromechanics is simulation, which connects computational models of neural circuits to models of an animal's body situated in a virtual physical world. This connection closes the feedback loop that links the brain, the body, and the world through sensory stimuli, muscle contractions, and body movement. Neuromechanical simulations enable investigators to explore the dynamical relationships between the brain, the body, and the world in ways that are difficult or impossible through experiment alone. Studies in a variety of animals have permitted the analysis of extremely complex and dynamic neuromechanical systems, they have demonstrated that the nervous system functions synergistically with the mechanical properties of the body, they have examined hypotheses that are difficult to test experimentally, and they have explored the role of sensory feedback in controlling complex mechanical systems with many degrees of freedom. Each of these studies confronts a common set of questions: (i) how to abstract key features of the body, the world and the CNS in a useful model, (ii) how to ground model parameters in experimental reality, (iii) how to optimize the model and identify points of sensitivity and insensitivity, and (iv) how to share neuromechanical models for examination, testing, and extension by others. PMID:20700384
Comparing simulation results of SBML capable simulators
Bergmann, Frank T.; Sauro, Herbert M.
2008-01-01
Motivation: Simulations are an essential tool when analyzing biochemical networks. Researchers and developers seeking to refine simulation tools or develop new ones would benefit greatly from being able to compare their simulation results. Summary: We present an approach to compare simulation results between several SBML capable simulators and provide a website for the community to share simulation results. Availability: The website with simulation results and additional material can be found under: http://sys-bio.org/sbwWiki/compare. The software used to generate the simulation results is available on the website for download. Contact: fbergman@u.washington.edu PMID:18579569
Introduction to Quantum Simulation
NASA Technical Reports Server (NTRS)
Williams, Colin P.
2005-01-01
This viewgraph presentation addresses the problem of efficiently simulating the evolution of a quantum system. The contents include: 1) Quantum Simulation; 2) Extracting Answers from Quantum Simulations; 3) Quantum Fourier Transform; 4) Eigenvalue Estimation; 5) Fermionic Simulations.
Puibasset, Joël
2005-04-28
Materials presenting nanoscale porosity are able to condense gases in their structure. This "capillary condensation" phenomenon has been studied for more than one century. Theoretical models help to understand experimental results but fail in explaining all experimental features. Most of the time, the difficulties in making quantitative or even qualitative predictions are due to the geometric complexity of the porous materials, such as large pore size distribution, chemical heterogeneities, or pore interconnections. Numerical calculations (lattice gas models or molecular simulations) are of considerable interest to calculate the adsorption properties of a fluid confined in a porous model with characteristic sizes up to several tens of nanometers. For instance, the grand canonical Monte Carlo method allows one to compute the average amount of fluid adsorbed in the porous model as a function of the temperature and the chemical potential of the fluid. However, the grand potential, necessary for a complete characterization of the system, is not a direct output of the algorithm. It is shown in this paper that the use of the isobaric-isothermal (NPT) ensemble allows one to circumvent this problem; that is, it is possible to get in one single Monte Carlo run the absolute grand potential for any given thermodynamic state of the fluid. A simplified thermodynamic integration scheme is then used to evaluate the grand potential over the whole isotherm branch passing through this initially given point. Since the usual NPT technique is a priori limited to homogeneous pores, it is proposed, for the first time, to generalize this procedure to a pore presenting a chemical heterogeneity along its axis. The new method gives the same results as the previous for homogeneous pores and allows new predictions for chemically heterogeneous pores. Comparison with the full integration scheme shows that the proposed direct calculation is faster since it avoids multiple Monte Carlo runs and
Meakin, Paul; Tartakovsky, Alexandre M.
2009-01-01
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
Paul Meakin; Alexandre Tartakovsky
2009-07-01
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
NASA Astrophysics Data System (ADS)
Unemi, Tatsuo
This chapter describes a basic framework of simulated breeding, a type of interactive evolutionary computing to breed artifacts, whose origin is Blind Watchmaker by Dawkins. These methods make it easy for humans to design a complex object adapted to his/her subjective criteria, just similarly to agricultural products we have been developing over thousands of years. Starting from randomly initialized genome, the solution candidates are improved through several generations with artificial selection. The graphical user interface helps the process of breeding with techniques of multifield user interface and partial breeding. The former improves the diversity of individuals that prevents being trapped at local optimum. The latter makes it possible for the user to fix features he/she already satisfied. These methods were examined through artistic applications by the author: SBART for graphics art and SBEAT for music. Combining with a direct genome editor and exportation to another graphical or musical tool on the computer, they can be powerful tools for artistic creation. These systems may contribute to the creation of a type of new culture.
ERIC Educational Resources Information Center
Heyman, Mark
1982-01-01
Simulation games are instructional techniques which create a social environment in which participants become involved with whatever resources they have. Discusses: (1) definitions of game, simulation, simulation game, and role playing; (2) advantages/disadvantages of simulation games; and (3) grading simulation games. (Author/JN)
Software simulator for multiple computer simulation system
NASA Technical Reports Server (NTRS)
Ogrady, E. P.
1983-01-01
A description is given of the structure and use of a computer program that simulates the operation of a parallel processor simulation system. The program is part of an investigation to determine algorithms that are suitable for simulating continous systems on a parallel processor configuration. The simulator is designed to accurately simulate the problem-solving phase of a simulation study. Care has been taken to ensure the integrity and correctness of data exchanges and to correctly sequence periods of computation and periods of data exchange. It is pointed out that the functions performed during a problem-setup phase or a reset phase are not simulated. In particular, there is no attempt to simulate the downloading process that loads object code into the local, transfer, and mapping memories of processing elements or the memories of the run control processor and the system control processor. The main program of the simulator carries out some problem-setup functions of the system control processor in that it requests the user to enter values for simulation system parameters and problem parameters. The method by which these values are transferred to the other processors, however, is not simulated.
Successful Simulations for Health Education.
ERIC Educational Resources Information Center
Hoban, J. Dennis
1978-01-01
Describes the use of simulation to improve the effectiveness of health education. The types of simulation described include written simulations, simulated patients, audiovisual simulations, computer simulations, and mannequins. (CMV)
NASA Technical Reports Server (NTRS)
Bartlett, R. G.; Hendricks, C. M.
1972-01-01
Metabolic simulation combustion chamber was developed as subsystem for breathing metabolic simulator. Entire system is used for evaluation of life support and resuscitation equipment. Metabolism subsystem simulates a human by consuming oxygen and producing carbon dioxide. Basic function is to simulate human metabolic range from rest to hard work.
Some Dimensions of Simulation.
ERIC Educational Resources Information Center
Beck, Isabel; Monroe, Bruce
Beginning with definitions of "simulation" (a methodology for testing alternative decisions under hypothetical conditions), this paper focuses on the use of simulation as an instructional method, pointing out the relationships and differences between role playing, games, and simulation. The term "simulation games" is explored with an analysis of…
COCOA: Simulating Observations of Star Cluster Simulations
NASA Astrophysics Data System (ADS)
Askar, Abbas; Giersz, Mirek; Pych, Wojciech; Dalessandro, Emanuele
2017-03-01
COCOA (Cluster simulatiOn Comparison with ObservAtions) creates idealized mock photometric observations using results from numerical simulations of star cluster evolution. COCOA is able to present the output of realistic numerical simulations of star clusters carried out using Monte Carlo or N-body codes in a way that is useful for direct comparison with photometric observations. The code can simulate optical observations from simulation snapshots in which positions and magnitudes of objects are known. The parameters for simulating the observations can be adjusted to mimic telescopes of various sizes. COCOA also has a photometry pipeline that can use standalone versions of DAOPHOT (ascl:1104.011) and ALLSTAR to produce photometric catalogs for all observed stars.
Systems Engineering Simulator (SES) Simulator Planning Guide
NASA Technical Reports Server (NTRS)
McFarlane, Michael
2011-01-01
The simulation process, milestones and inputs are unknowns to first-time users of the SES. The Simulator Planning Guide aids in establishing expectations for both NASA and non-NASA facility customers. The potential audience for this guide includes both internal and commercial spaceflight hardware/software developers. It is intended to assist their engineering personnel in simulation planning and execution. Material covered includes a roadmap of the simulation process, roles and responsibilities of facility and user, major milestones, facility capabilities, and inputs required by the facility. Samples of deliverables, facility interfaces, and inputs necessary to define scope, cost, and schedule are included as an appendix to the guide.
NASA Technical Reports Server (NTRS)
1963-01-01
Rendezvous Docking Simulator. The simulation demonstrated linear and gimbal motions of the capsule and a Gemini-Agena docking. [Entire movie available on DVD from CASI as Doc ID 20070030983. Contact help@sti.nasa.gov
NASA Technical Reports Server (NTRS)
Goswami, Kumar K.; Iyer, Ravishankar K.
1990-01-01
Discrete event-driven simulation makes it possible to model a computer system in detail. However, such simulation models can require a significant time to execute. This is especially true when modeling large parallel or distributed systems containing many processors and a complex communication network. One solution is to distribute the simulation over several processors. If enough parallelism is achieved, large simulation models can be efficiently executed. This study proposes a distributed simulator called DSIM which can run on various architectures. A simulated test environment is used to verify and characterize the performance of DSIM. The results of the experiments indicate that speedup is application-dependent and, in DSIM's case, is also dependent on how the simulation model is distributed among the processors. Furthermore, the experiments reveal that the communication overhead of ethernet-based distributed systems makes it difficult to achieve reasonable speedup unless the simulation model is computation bound.
NASA Technical Reports Server (NTRS)
Kavaya, M. J.
1985-01-01
Transfer function simulator constructed from analog or both analog and digital components substitute for device that has faults that confound analysis of feedback control loop. Simulator is substitute for laser and spectrophone.
The Business Flight Simulator.
ERIC Educational Resources Information Center
Dwyer, P.; Simpson, D.
1989-01-01
The authors describe a simulation program based on a workshop approach designed for postsecondary business students. Features and benefits of the workshop technique are discussed. The authors cover practical aspects of designing and implementing simulation workshops. (CH)
Remote manipulator dynamic simulation
NASA Technical Reports Server (NTRS)
Wild, E. C.; Donges, P. K.; Garand, W. A.
1972-01-01
A simulator to generate the real time visual scenes required to perform man in the loop investigations of remote manipulator application and design concepts for the space shuttle is described. The simulated remote manipulator consists of a computed display system that uses a digital computer, the electronic scene generator, an operator's station, and associated interface hardware. A description of the capabilities of the implemented simulation is presented. The mathematical models and programs developed for the simulation are included.
NASA Technical Reports Server (NTRS)
Bahrami, K. A.; Kirkham, H.; Rahman, S.
1986-01-01
In a series of tests performed under the Department of Energy auspices, power line carrier propagation was observed to be anomalous under certain circumstances. To investigate the cause, a distribution system simulator was constructed. The simulator was a physical simulator that accurately represented the distribution system from below power frequency to above 50 kHz. Effects such as phase-to-phase coupling and skin effect were modeled. Construction details of the simulator, and experimental results from its use are presented.
Launch Vehicle Operations Simulator
NASA Technical Reports Server (NTRS)
Blackledge, J. W.
1974-01-01
The Saturn Launch Vehicle Operations Simulator (LVOS) was developed for NASA at Kennedy Space Center. LVOS simulates the Saturn launch vehicle and its ground support equipment. The simulator was intended primarily to be used as a launch crew trainer but it is also being used for test procedure and software validation. A NASA/contractor team of engineers and programmers implemented the simulator after the Apollo XI lunar landing during the low activity periods between launches.
Microgravity Simulation Facility (MSF)
NASA Technical Reports Server (NTRS)
Richards, Stephanie E. (Compiler); Levine, Howard G.; Zhang, Ye
2016-01-01
The Microgravity Simulator Facility (MSF) at Kennedy Space Center (KSC) was established to support visiting scientists for short duration studies utilizing a variety of microgravity simulator devices that negate the directional influence of the "g" vector (providing simulated conditions of micro or partial gravity). KSC gravity simulators can be accommodated within controlled environment chambers allowing investigators to customize and monitor environmental conditions such as temperature, humidity, CO2, and light exposure.
NASA Astrophysics Data System (ADS)
Knight, J. D.; Lynch, R. L.; Pyles, D. A.; Seitz, R. N.; Thornton, T. V.
1982-07-01
Pershing 2 flight simulations were performed using the U70 missile simulation program to determine (1) in the event of an accidental nozzle deflection, how fast the missile would leave its (safe) flight corridor; (2) how well the U70 aerodynamic simulation matches the actual flight data; and (3) the trajectory profiles for nine Tactical Ballistic Missile flight trajectories. Also an advanced simulation program developed by TRW, Inc. was partially converted to run on an inhouse computer.
1983-05-24
S83-32568 (23 May 1983) --- Astronaut Sally K. Ride, STS-7 mission specialist, straps herself into a seat in the Shuttle Mission Simulator (SMS) in Johnson Space Center?s Mission Simulation and Training Facility. Dr. Ride and the other STS-7 crew members continue their simulations in the motion base simulator in preparation for their flight in the space shuttle Challenger. Launch is scheduled for June 18. Troy Stewart, suit technician, assisted Dr. Ride. Photo credit: NASA
Burr, Melvin J.
1990-01-30
An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.
Computerized Simulation: An Overview.
ERIC Educational Resources Information Center
Crookall, David
1988-01-01
This article outlines issues and practices related to the philosophy of simulations and the relationship between traditional simulation techniques and computer technology. Introduces the articles in this special issue and concludes by discussing various problems related to computer simulation, modeling, design, and evaluation. (Author/BSR)
Electrical Circuit Simulation Code
Wix, Steven D.; Waters, Arlon J.; Shirley, David
2001-08-09
Massively-Parallel Electrical Circuit Simulation Code. CHILESPICE is a massively-arallel distributed-memory electrical circuit simulation tool that contains many enhanced radiation, time-based, and thermal features and models. Large scale electronic circuit simulation. Shared memory, parallel processing, enhance convergence. Sandia specific device models.
Today's Business Simulation Industry
ERIC Educational Resources Information Center
Summers, Gary J.
2004-01-01
New technologies are transforming the business simulation industry. The technologies come from research in computational fields of science, and they endow simulations with new capabilities and qualities. These capabilities and qualities include computerized behavioral simulations, online feedback and coaching, advanced interfaces, learning on…
CAISSON: Interconnect Network Simulator
NASA Technical Reports Server (NTRS)
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.
NASA Technical Reports Server (NTRS)
Bartlett, R. G., Jr.; Hendricks, C. M.; Morison, W. B.
1972-01-01
A description is given of an automatic computer controlled second generation breathing metabolic simulator (BMS). The simulator is used for evaluating and testing respiratory diagnostic, monitoring, support, and resuscitation equipment. Any desired sequence of metabolic activities can be simulated on the device for up to 15 hours. The computer monitors test procedures and provides printouts of test results.
A mathematical and numerical model is developed to simulate the transport and fate of NAPLs (Non-Aqueous Phase Liquids) in near-surface granular soils. The resulting three-dimensional, three phase simulator is called NAPL. The simulator accommodates three mobile phases: water, NA...
Simulating Supernova Light Curves
Even, Wesley Paul; Dolence, Joshua C.
2016-05-05
This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.
ERIC Educational Resources Information Center
Drayer, Joris; Rascher, Dan
2010-01-01
Simulations have long been used in business schools to give students experience making real-world decisions in a relatively low risk environment. The OAKLAND A'S BASEBALL BUSINESS SIMULATOR takes a traditional business simulation and applies it to the sport industry, in which sales of tangible products are replaced by sales of experiences provided…
NASA Technical Reports Server (NTRS)
Wood, Charles C.
1991-01-01
The following topics are presented in tabular form: (1) simulation capability assessments (no propulsion system test); (2) advanced vehicle simulation capability assessment; (3) systems tests identified events; (4) main propulsion test article (MPTA) testing evaluation; (5) Saturn 5, 1B, and 1 testing evaluation. Special vehicle simulation issues that are propulsion related are briefly addressed.
Burr, M.J.
1989-03-01
An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.
Burr, M.J.
1990-01-30
This patent describes an arc voltage simulator for an arc welder which permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.
ERIC Educational Resources Information Center
Herbert, David; Sturtridge, Gill
Simulation, including role-playing and role-simulation, as techniques for teaching English as a second language are discussed and illustrated. Introductory sections outline the instructional value of simulations, their motivating function, stages in their production, and their structure. Their production includes these stages: analysis of student…
A mathematical and numerical model is developed to simulate the transport and fate of NAPLs (Non-Aqueous Phase Liquids) in near-surface granular soils. The resulting three-dimensional, three phase simulator is called NAPL. The simulator accommodates three mobile phases: water, NA...
NASA Technical Reports Server (NTRS)
1981-01-01
By adapting COSMIC's One-on-One Adaptive Maneuvering Logic (AML) for two versus one simulation, Link Division was able to reduce software and other design/development costs. Enhancements to the AML program developed by Link for simulation of two-versus one combat, two trainees can simultaneously engage a computer driven target, thereby doubling the training utility of the simulator.
Conducting Effective Simulator Training.
ERIC Educational Resources Information Center
Gerling, Kenneth D.
This paper describes the simulator phase of Commonwealth Edison's program for training and licensing operators of nuclear power stations. Topics covered include (1) preparing the students before starting the simulator phase; (2) the simulator schedule and the number of students that can be trained effectively in a class; (3) format and structure…
Digital Simulation in Education.
ERIC Educational Resources Information Center
Braun, Ludwig
Simulation as a mode of computer use in instruction has been neglected by educators. This paper briefly explores the circumstances in which simulations are useful and presents several examples of simulation programs currently being used in high-school biology, chemistry, physics, and social studies classes. One program, STERIL, which simulates…
ERIC Educational Resources Information Center
Drayer, Joris; Rascher, Dan
2010-01-01
Simulations have long been used in business schools to give students experience making real-world decisions in a relatively low risk environment. The OAKLAND A'S BASEBALL BUSINESS SIMULATOR takes a traditional business simulation and applies it to the sport industry, in which sales of tangible products are replaced by sales of experiences provided…
Today's Business Simulation Industry
ERIC Educational Resources Information Center
Summers, Gary J.
2004-01-01
New technologies are transforming the business simulation industry. The technologies come from research in computational fields of science, and they endow simulations with new capabilities and qualities. These capabilities and qualities include computerized behavioral simulations, online feedback and coaching, advanced interfaces, learning on…
Experimental quantum channel simulation
NASA Astrophysics Data System (ADS)
Lu, He; Liu, Chang; Wang, Dong-Sheng; Chen, Luo-Kan; Li, Zheng-Da; Yao, Xing-Can; Li, Li; Liu, Nai-Le; Peng, Cheng-Zhi; Sanders, Barry C.; Chen, Yu-Ao; Pan, Jian-Wei
2017-04-01
Quantum simulation is of great importance in quantum information science. Here, we report an experimental quantum channel simulator imbued with an algorithm for imitating the behavior of a general class of quantum systems. The reported quantum channel simulator consists of four single-qubit gates and one controlled-not gate. All types of quantum channels can be decomposed by the algorithm and implemented on this device. We deploy our system to simulate various quantum channels, such as quantum-noise channels and weak quantum measurement. Our results advance experimental quantum channel simulation, which is integral to the goal of quantum information processing.
Simulation in Surgical Education
de Montbrun, Sandra L.; MacRae, Helen
2012-01-01
The pedagogical approach to surgical training has changed significantly over the past few decades. No longer are surgical skills solely acquired through a traditional apprenticeship model of training. The acquisition of many technical and nontechnical skills is moving from the operating room to the surgical skills laboratory through the use of simulation. Many platforms exist for the learning and assessment of surgical skills. In this article, the authors provide a broad overview of some of the currently available surgical simulation modalities including bench-top models, laparoscopic simulators, simulation for new surgical technologies, and simulation for nontechnical surgical skills. PMID:23997671
Alania, Marco; Gomez, Adolfo V. Chamorro; Araya, Ignacio J.; Huerta, Humberto Martinez; Flores, Alejandra Parra; Knapp, Johannes
2009-04-30
Air shower simulations are a vital part of the design of air shower experiments and the analysis of their data. We describe the basic features of air showers and explain why numerical simulations are the appropriate approach to model the shower simulation. The CORSIKA program, the standard simulation program in this field, is introduced and its features, performance and limitations are discussed. The basic principles of hadronic interaction models and some gerneral simulation techniques are explained. Also a brief introduction to the installation and use of CORSIKA is given.
Advanced electromagnetic gun simulation
NASA Astrophysics Data System (ADS)
Brown, J. L.; George, E. B.; Lippert, J. R.; Balius, A. R.
1986-11-01
The architecture, software and application of a simulation system for evaluating electromagnetic gun (EMG) operability, maintainability, test data and performance tradeoffs are described. The system features a generic preprocessor designed for handling the large data rates necessary for EMG simulations. The preprocessor and postprocessor operate independent of the EMG simulation, which is viewed through windows by the user, who can then select the areas of the simulation desired. The simulation considers a homopolar generator, busbars, pulse shaping coils, the barrel, switches, and prime movers. In particular, account is taken of barrel loading by the magnetic field, Lorentz force and plasma pressure.
Creating a Simulated Pharmacy.
Soto, Cory; Stiner, Jamie; Noji, Daniel O; Rusheen, Jeffrey M; Huang, Yue Ming
2016-06-01
The acquisition and use of pharmaceuticals in simulation is a common challenge for many institutions and simulation centers. There are 2 major avenues of obtaining medications, namely, via expired drugs donated by manufacturers or via purchasing simulated medication vials filled with inactive ingredients. Neither option is ideal to keep pace with busy simulation centers or to meet the specialized requirements of many educational programs. We describe an alternative solution through internal production of simulated drugs using readily available materials from laboratory suppliers. Serum vials, stoppers, and flip off vial caps can be purchased in 2-, 5-, 10-, and 20-mL volumes. Vials can be filled with substances such as 0.9% NaCl or table salt to mimic a variety of available injectable drugs. Labels can be produced using the free online Web application, Simulated Online Pharmaceutical Image Editor (SOPHIE) and printed on glossy adhesive photo paper for application onto completed vials. A wide range of simulated drugs, customized to the needs of each center, can be produced in an affordable and reliable manner. The appearance of the vials can be tailored for each program to meet educational objectives and enhance fidelity in simulation. Low-cost production of simulated drug vials increases learning opportunities for participants to practice skills related to drug delivery and preparation. Further expansion can include nonintravenous drugs, code syringes, or reconstitution devices used for blood factors. Simulation centers should consider safety, availability, affordability, and fidelity concerns before integrating an in-house simulated pharmacy.
Simulation verification techniques study
NASA Technical Reports Server (NTRS)
Schoonmaker, P. B.; Wenglinski, T. H.
1975-01-01
Results are summarized of the simulation verification techniques study which consisted of two tasks: to develop techniques for simulator hardware checkout and to develop techniques for simulation performance verification (validation). The hardware verification task involved definition of simulation hardware (hardware units and integrated simulator configurations), survey of current hardware self-test techniques, and definition of hardware and software techniques for checkout of simulator subsystems. The performance verification task included definition of simulation performance parameters (and critical performance parameters), definition of methods for establishing standards of performance (sources of reference data or validation), and definition of methods for validating performance. Both major tasks included definition of verification software and assessment of verification data base impact. An annotated bibliography of all documents generated during this study is provided.
Computer simulation of bulk and surface chemical diffusion of light atoms in metals
Murch, G.E.
1981-01-01
The lattice gas as a model for interstitial solid solution and adsorption systems is reviewed with emphasis on the generation of ordered structures. Then, as a prelude to the main discourse on chemical diffusion, the tracer diffusion coefficient is discussed in conjunction with the presentation of Monte Carlo results. Next, chemical diffusion is treated in detail with emphasis on the Danken equation. Monte Carlo results are then presented for the chemical diffusion coefficient. The large maximum in the chemical diffusivity observed within the ordered phase is traced back to the very strong driving force provided by the chemical potential derivative.
Simulation in Health Sciences Education.
ERIC Educational Resources Information Center
Norman, Geoffrey R.; And Others
1985-01-01
Reviews five simulation methods used in medical and health science education: oral examinations, live simulated patients, mannequins, and written and computer-based simulations. Each type of simulation is discussed relative to its fidelity, reliability, validity, learning, and feasibility. (MBR)
NASA Astrophysics Data System (ADS)
Catan, M. A.
A simulator was utilized to provide controlled-temperature sources and sinks to an experimental water-to-water laboratory heat pump test bed. This combination was used to demonstrate and explore the potential of the vapor-compression cycle to deliver high COP's at SAHP source temperatures. Results from the simulator were used in computer simulations of complete systems performed by BNL, by the SAHP contractors, and by others. A two-speed compressor was first tested at high source temperatures on the BNL simulator. In view of the decision by both contractors to construct water-to-air (rather than water-to-water) heat pumps, the BNL simulator was fitted with an air-side test loop. The prototype heat pump was tested under steady-state conditions on the BNL simulator.
Instrumented Architectural Simulation System
NASA Technical Reports Server (NTRS)
Delagi, B. A.; Saraiya, N.; Nishimura, S.; Byrd, G.
1987-01-01
Simulation of systems at an architectural level can offer an effective way to study critical design choices if (1) the performance of the simulator is adequate to examine designs executing significant code bodies, not just toy problems or small application fragements, (2) the details of the simulation include the critical details of the design, (3) the view of the design presented by the simulator instrumentation leads to useful insights on the problems with the design, and (4) there is enough flexibility in the simulation system so that the asking of unplanned questions is not suppressed by the weight of the mechanics involved in making changes either in the design or its measurement. A simulation system with these goals is described together with the approach to its implementation. Its application to the study of a particular class of multiprocessor hardware system architectures is illustrated.
Simulation integration with confidence
NASA Astrophysics Data System (ADS)
Strelich, Tom; Stalcup, Bruce W.
1999-07-01
Current financial, schedule and risk constraints mandate reuse of software components when building large-scale simulations. While integration of simulation components into larger systems is a well-understood process, it is extremely difficult to do while ensuring that the results are correct. Illgen Simulation Technologies Incorporated and Litton PRC have joined forces to provide tools to integrate simulations with confidence. Illgen Simulation Technologies has developed an extensible and scaleable, n-tier, client- server, distributed software framework for integrating legacy simulations, models, tools, utilities, and databases. By utilizing the Internet, Java, and the Common Object Request Brokering Architecture as the core implementation technologies, the framework provides built-in scalability and extensibility.
Liss, Michael A; McDougall, Elspeth M
2013-01-01
Robotic surgery has undergone exponential growth and has ever developing utilization. The explosion of new technologies and regulation have led to challenges in training surgeons who desire this skill set. We review the current state of robotic simulation and incorporation of simulation into surgical training curricula. In addition to the literature review, results of a questionnaire survey study of 21 expert and novice surgeons attending a Urologic Robotic Oncology conference using 3 different robotic skill simulation devices are discussed. An increasing number of robotic surgery simulators have had some degree of validation study of their use in surgical education curricula and proficiency testing. Although simulators are advantageous, confirmation of construct and predictive validity of robotic simulators and their reliability as a training tool will be necessary before they are integrated into the surgical credentialing process.
Simulation in laparoscopic surgery.
León Ferrufino, Felipe; Varas Cohen, Julián; Buckel Schaffner, Erwin; Crovari Eulufi, Fernando; Pimentel Müller, Fernando; Martínez Castillo, Jorge; Jarufe Cassis, Nicolás; Boza Wilson, Camilo
2015-01-01
Nowadays surgical trainees are faced with a more reduced surgical practice, due to legal limitations and work hourly constraints. Also, currently surgeons are expected to dominate more complex techniques such as laparoscopy. Simulation emerges as a complementary learning tool in laparoscopic surgery, by training in a safe, controlled and standardized environment, without jeopardizing patient' safety. Simulation' objective is that the skills acquired should be transferred to the operating room, allowing reduction of learning curves. The use of simulation has increased worldwide, becoming an important tool in different surgical residency programs and laparoscopic training courses. For several countries, the approval of these training courses are a prerequisite for the acquisition of surgeon title certifications. This article reviews the most important aspects of simulation in laparoscopic surgery, including the most used simulators and training programs, as well as the learning methodologies and the different key ways to assess learning in simulation.
NASA Astrophysics Data System (ADS)
Danišovič, Peter; Schlosser, František; Šrámek, Juraj; Rázga, Martin
2015-05-01
A Tunnel Traffic & Operation Simulator is a device of the Centre of Transport Research at the University of Žilina. The Simulator allows managing technological equipment of virtual two-tube highway tunnel, which is interconnected with simulation of vehicle traffic in tunnel. Changes of the traffic-operation states and other equipment are reflecting at the simulated traffic, as well as simulations of various emergency events in traffic initiate changes in tunnel detecting and measuring devices. It is thus possible to simulate emergency states, which can be affected by various faults of technology as well as by climatic conditions. The solutions can be found in irreplaceable experiences of Slovak road tunnel operators, changes of trafficoperation states, visualizations of operator technological display screens, technological devices labelling in order to increase operational safety of road tunnels.
[Simulation training in ophthalmology].
Serna-Ojeda, Juan Carlos; Graue-Hernández, Enrique O; Guzmán-Salas, Pablo José; Rodríguez-Loaiza, José Luis
2017-01-01
Simulation in medicine is an indispensable tool to improve doctors' responses to different situations, enhancing their performance. However, simulation in ophthalmology is a very recent trend, mainly because of the high complexity of developing newer teaching tools, with the need for highly realistic models, mostly in surgical ophthalmic simulation. The whole development of simulation in ophthalmology, from the very first attempts that used basic models, to the newer virtual reality models, allows for a comprehensive, faster, and more efficient development of skills necessary in basic and advance procedures in ophthalmology, creating a better learning environment, improving costs, and developing a very promising panorama, in which simulation can be incorporated in teaching programs all around the globe. Simulation in ophthalmology allows for better results in the formation of ophthalmologists, and it is becoming a new tool to achieve better results in medical and surgical procedures, thus improving outcomes and quality of care.
Parallel Atomistic Simulations
HEFFELFINGER,GRANT S.
2000-01-18
Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.
NASA Technical Reports Server (NTRS)
Olasky, C.
1980-01-01
The simulator was designed to provide real time simulation capability for all phases of the Shuttle Transportation System orbital missions including prelaunch, ascent, onorbit operations, deorbit, entry, approach/landing, and rollout. Full mission continuity is provided in transition between these mission phases. Dual fixed and motion base crew stations, instructor/operator stations, and computer systems allow parallel, simultaneous crew training with either complex capable of being individually integrated with the mission control center. This integrated training capability allows flight control personnel training in the air/ground interface areas of tracking, telemetry (vehicle systems monitoring), uplink command control, and communications. With the exception of the simulated Data Processing System, which utilizes actual flight computers and associated flight software, all orbiter onboard systems are functionally simulated with extensive simulated malfunction capabilities. Additionally, crew out-the-window visual scenes, and aural cues are rigorously simulated.
ARFORGEN BOG: Dwell Simulation
2011-07-11
contracted programming support from ProModel , the simulation run time has been significantly reduced. The largest CMF (11 Series) can be simulated...consummate professional Mr. Steve Courtney. A senior consultant with the ProModel Corporation, Steve has been absolutely fundamental as the architect...stated goal. At the request of the Army’s Human Resources Leadership, MAJ Dabkowski and MAJ Zais built a model (using ProModel © simulation software
The Sandia Lightning Simulator.
Martinez, Leonard E.; Caldwell, Michele
2005-01-01
The Sandia Lightning Simulator at Sandia National Laboratories can provide up to 200 kA for a simulated single lightning stroke, 100 kA for a subsequent stroke, and hundreds of Amperes of continuing current. It has recently been recommissioned after a decade of inactivity and the single-stroke capability demonstrated. The simulator capabilities, basic design components, upgrades, and diagnostic capabilities are discussed in this paper.
Instrumented Architectural Simulation
1987-11-01
architectural level can offer an effective way to study critical design choices if (1) the performance of the simulator is adequate to examine designs...attribute of the underlying Lisp base of the simulation system that changes in these definitions have immediate effect even during a simulation run...methods for a component, the concerns surrounding component design are effectively partitioned from component instrumentation. Panels are put together
1979-10-04
S79-37006 (29 Sept. 1979) --- Astronaut John W. Young, commander of STS-1, goes through a simulation exercises in the shuttle mission simulator (SMS) in the mission simulation and training facility at NASA's Johnson Space Center (JSC). Young and astronaut Robert L. Crippen, prime crew pilot, are in training for the first of series of orbital test missions aboard the Columbia. Photo credit: NASA
Nanoelectronic Device Simulator Nanodev
NASA Astrophysics Data System (ADS)
Novik, E. G.; Sheremet, I. V.; Ivashkevich, S. S.; Abramov, I. I.
In this paper the models for simulation of single-electron (Coulomb blockade) and resonant tunneling structures are described. To calculate various parameters and characteristics (current-voltage characteristics, parameters of operation and others) of these structures algorithms and programs have been developed. The simulator NANODEV consists of two modeling units for Coulomb blockade and for resonant tunneling devices. Some calculation results are also present. The simulator was developed for PC computers.
Floren, John
2012-03-19
The All People's Simulator is a software package which can simulate a large number of people wandering randomly through a real city. It utilizes freely-available map data from the OpenStreetMaps project to create a map of city streets, then simulates people wandering through those streets. APS was designed to integrate with other work being done in the "Megadroid" LDRD, but is capable of functioning and providing value completely on its own.
Constructing emotion through simulation.
Wilson-Mendenhall, Christine D
2017-07-21
Evidence increasingly suggests that simulations implement patterns of prior experience to construct one's current experience, whether that experience is oriented in the past, in the here and now, or in the future. Simulation is the mechanism by which the brain capitalizes on prior learning to efficiently navigate the situation at hand. This review examines the latest developments in theory and empirical research that address simulation during emotional phenomena. Integration of evidence across multiple literatures suggests that simulation accounts provide a unifying framework across many different emotional phenomena and highlights the importance of investigating dynamics, complexity, and variation in emotional experiences moving forward. Copyright © 2017 Elsevier Ltd. All rights reserved.
A photovoltaic array simulator
NASA Astrophysics Data System (ADS)
Vachtsevanos, G. J.; Grimbas, E. J.
A system simulating the output voltage-current characteristics of a photovoltaic array is described. The simulator may be used to test the performance of PV arrays and associated power conditioning equipment necessary for the autonomous or interconnected operation of photovoltaic energy sources. The simulator's main features include simplicity of construction, wide parametric variability and low cost. It is capable of reproducing the output characteristics of commercially available arrays at varying solar irradiation levels with sufficient accuracy. The design ensures the lowest possible power dissipation and minimal thermal drift. It is estimated that the cost of the simulator is an insignificant fraction of the actual array cost in the kilowatt power range.
Helicopter simulator standards
NASA Technical Reports Server (NTRS)
Boothe, Edward M.
1992-01-01
The initial advisory circular was produced in 1984 (AC 120-XX). It was not finalized, however, because the FAR's for pilot certification did not recognize helicopter simulators and, therefore, permitted no credit for their use. That is being rectified, and, when the new rules are published, standards must be available for qualifying simulators. Because of the lack of a data base to support specification of these standards, the FAA must rely on the knowledge of experts in the simulator/training industry. A major aim of this workshop is to form a working group of these experts to produce a set of standards for helicopter training simulators.
Aviation Safety Simulation Model
NASA Technical Reports Server (NTRS)
Houser, Scott; Yackovetsky, Robert (Technical Monitor)
2001-01-01
The Aviation Safety Simulation Model is a software tool that enables users to configure a terrain, a flight path, and an aircraft and simulate the aircraft's flight along the path. The simulation monitors the aircraft's proximity to terrain obstructions, and reports when the aircraft violates accepted minimum distances from an obstruction. This model design facilitates future enhancements to address other flight safety issues, particularly air and runway traffic scenarios. This report shows the user how to build a simulation scenario and run it. It also explains the model's output.
ERIC Educational Resources Information Center
Ferrari, Pier Alda; Barbiero, Alessandro
2012-01-01
The increasing use of ordinal variables in different fields has led to the introduction of new statistical methods for their analysis. The performance of these methods needs to be investigated under a number of experimental conditions. Procedures to simulate from ordinal variables are then required. In this article, we deal with simulation from…
ERIC Educational Resources Information Center
Dormans, Joris
2011-01-01
Realism remains a prominent topic in game design and industry research; yet, a strong academic case can be made that games are anything, but realistic. This article frames realism in games in semiotic terms as iconic simulation and argues that games can gain expressiveness when they move beyond the current focus on iconic simulation. In parallel…
Pete Humphrey, Charles Babb
2012-01-05
The MRDIS Simulator is a software application to duplicate the tcp/ip output normally produced by a Mobile Radiation Detection and Identification System (MRDIS) radiation detector. Output simulates the data stream from TSA radiation detectors plus OCR data from AsiaVision OCR systems (used by the actual MRDIS).
ERIC Educational Resources Information Center
Engelhardt, Lucas M.
2015-01-01
In this article, the author presents a price-takers' market simulation geared toward principles-level students. This simulation demonstrates that price-taking behavior is a natural result of the conditions that create perfect competition. In trials, there is a significant degree of price convergence in just three or four rounds. Students find this…
2014-04-01
Damselfly is a model-based parallel network simulator. It can simulate communication patterns of High Performance Computing applications on different network topologies. It outputs steady-state network traffic for a communication pattern, which can help in studying network congestion and its impact on performance.
NASA Astrophysics Data System (ADS)
Boixo, Sergio; Somma, Rolando; Barnum, Howard
2008-03-01
We develop a quantum algorithm to solve combinatorial optimization problems through quantum simulation of a classical annealing process. Our algorithm combines techniques from quantum walks and quantum phase estimation, and can be viewed as the quantum analogue of the discrete-time Markov Chain Monte Carlo implementation of classical simulated annealing.
ERIC Educational Resources Information Center
Engelhardt, Lucas M.
2015-01-01
In this article, the author presents a price-takers' market simulation geared toward principles-level students. This simulation demonstrates that price-taking behavior is a natural result of the conditions that create perfect competition. In trials, there is a significant degree of price convergence in just three or four rounds. Students find this…
Student Stimulation through Simulation
ERIC Educational Resources Information Center
Jaski, Ernest B.
1976-01-01
Describes the development, use, and outcomes of a simulation decision-making game designed to help close the classroom/business relevancy gap in a marketing course at Southwest College, Chicago. Notes plans for city-wide use of the successful simulation. (TA)
Cloud Scene Simulation Modeling
1991-11-20
PL-M-91-2295 AD-A256 689 CLOUD SCENE SIMULATION MODELING M.E. Cianciolo J.S. Hersh M.R Ramos-Johnson TASC 55 Walkers Brook Drive Reading...1991 Scientific No. 1 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Cloud Scene Simulation Modeling PE 62101F PR 6670 TA 09 WU BE 6. AUTHOR(S) Contract
Simulating Laboratory Procedures.
ERIC Educational Resources Information Center
Baker, J. E.; And Others
1986-01-01
Describes the use of computer assisted instruction in a medical microbiology course. Presents examples of how computer assisted instruction can present case histories in which the laboratory procedures are simulated. Discusses an authoring system used to prepare computer simulations and provides one example of a case history dealing with fractured…
Multicore Education through Simulation
ERIC Educational Resources Information Center
Ozturk, O.
2011-01-01
A project-oriented course for advanced undergraduate and graduate students is described for simulating multiple processor cores. Simics, a free simulator for academia, was utilized to enable students to explore computer architecture, operating systems, and hardware/software cosimulation. Motivation for including this course in the curriculum is…
VCSEL Applications and Simulation
NASA Technical Reports Server (NTRS)
Cheung, Samson; Goorjian, Peter; Ning, Cun-Zheng; Li, Jian-Zhong
2000-01-01
This viewgraph presentation gives an overview of Vertical Cavity Surface Emitting Laser (VCSEL) simulation and its applications. Details are given on the optical interconnection in information technology of VCSEL, the formulation of the simulation, its numeric algorithm, and the computational results.
Prototyping distributed simulation networks
NASA Technical Reports Server (NTRS)
Doubleday, Dennis L.
1990-01-01
Durra is a declarative language designed to support application-level programming. The use of Durra is illustrated to describe a simple distributed application: a simulation of a collection of networked vehicle simulators. It is shown how the language is used to describe the application, its components and structure, and how the runtime executive provides for the execution of the application.
NASA Technical Reports Server (NTRS)
Bartlett, R. G.; Hendricks, C. M.; Morison, W. B.
1972-01-01
Breathing-metabolic simulator was developed to be used for evaluation of life support equipment. Apparatus simulates human breathing rate and controls temperature and humidity of exhaled air as well as its chemical composition. All functions are designed to correspond to various degrees of human response.
Radio Channel Simulator (RCSM)
2007-01-31
This is a simulation package for making site specific predictions of radio signal strength. The software computes received power at discrete grid points as a function of the transmitter location and propagation environment. It is intended for use with wireless network simulation packages and to support wireless network deployments.
ERIC Educational Resources Information Center
Dormans, Joris
2011-01-01
Realism remains a prominent topic in game design and industry research; yet, a strong academic case can be made that games are anything, but realistic. This article frames realism in games in semiotic terms as iconic simulation and argues that games can gain expressiveness when they move beyond the current focus on iconic simulation. In parallel…
ERIC Educational Resources Information Center
Boocock, Sarane S., Ed.; Schild, E.O., Ed.
Simulation games serve many functions, but the important one to educators is that they present the student player with a real-life situation allowing him to use his knowledge and abilities while discovering decision-making skills for himself. To provide a basic reference on simulation gaming, essays on various aspects of games were collected from…
ERIC Educational Resources Information Center
Raymond, Chad; Usherwood, Simon
2013-01-01
Simulations are employed widely as teaching tools in political science, yet evidence of their pedagogical effectiveness, in comparison to other methods of instruction, is mixed. The assessment of learning outcomes is often a secondary concern in simulation design, and the qualitative and quantitative methods used to evaluate outcomes are…
Political Simulations Using Excel
ERIC Educational Resources Information Center
Jackson, Steven F.
2013-01-01
Simulations have received considerable attention as a tool to promote problem-solving skills, intense involvement, and high-order thinking among students. Whether semester-long exercises or a single-class session, simulations are often used in areas of conflict studies, diplomatic studies, trade disputes, electoral processes, and policy and legal…
ERIC Educational Resources Information Center
Laktasic, Stanley G.
Simulation is the duplication of the essential characteristics of a task or situation. It represents three elements of the teaching-learning process: (1) stimulus situation; (2) response; and (3) feedback. The uses of simulation may fall into one of three general categories: research--the generation of information about an operational or proposed…
Interactive Reactor Simulation.
ERIC Educational Resources Information Center
Nuttall, Herbert E., Jr.; Himmelblau, David M.
In the field of chemical engineering, interactive process models can simulate the dynamic behavior and analysis of chemical processes. DYFLO was the process simulation program selected as a foundation for development of interactive programs for computer-assisted instruction (CAI) in chemical engineering. Interactive Computing and time sharing…
1984-02-01
predicted in steady state theory . 0 The Army has decided on the basis of other arguments that 10% blockage is acceptable for a large blast simulator. These...Proceedings, 28-30 April 1965, p. 259. 16. Sanal , M4., Lindberg, H.E. and Colton, J.D., "Simulation of Blast Waves with Tailored Explosive Charges", SRI
NASA Astrophysics Data System (ADS)
Bauleo, P.; Bonifazi, C.; Filevich, A.
2004-01-01
The angular and energy resolutions of the TANGO Array were obtained using extensive Monte Carlo simulations performed with a double purpose: (1) to determine the appropriate parameters for the array fitting to the desired range of sensitivity (the knee energy region), and (2) to construct a reliable shower database required for reference in the analysis of experimental data. The AIRES code, with the SIBYLL hadronic collision package, was used to simulate Extended Air Showers produced by primary cosmic rays (assuming protons and iron nuclei), with energies ranging from 10 14 to 10 18 eV. These data were fed into a realistic code which simulates the response of the detectors (water Cherenkov detectors), including the electronics, pickup noise, and the signal attenuation in the connecting cables. The trigger stage was considered in the simulations in order to estimate the trigger efficiency of the array and to verify the accuracy of the reconstruction codes. This paper delineates the simulations performed to obtain the expected behavior of the array, and describes the simulated data. The results of these simulations suggest that we can expect an error in the energy of the primary cosmic-ray of ˜60% of the estimated value and that the error in the measurement of the direction of arrival can be estimated as ˜4°. The present simulations also indicate that unambiguous assignments of the primary energy cannot be obtained because of the uncertainty in the nature of the primary cosmic ray.
Weening, J.S.
1988-05-01
CSIM is a simulator for parallel Lisp, based on a continuation passing interpreter. It models a shared-memory multiprocessor executing programs written in Common Lisp, extended with several primitives for creating and controlling processes. This paper describes the structure of the simulator, measures its performance, and gives an example of its use with a parallel Lisp program.
1978-02-01
A brassboard training device that simulates the Dragon missile was developed and tested to evaluate the characteristics that are necessary for...improved training of Dragon gunners. Videotape recording and a full color simulation were found to be valuable as a training aid. An audible signal
NASA Technical Reports Server (NTRS)
Chapman, C. P.; Slusser, R. A.
1980-01-01
PARAMET, interactive simulation program for parametric studies of electric vehicles, guides user through simulation by menu and series of prompts for input parameters. Program considers aerodynamic drag, rolling resistance, linear and rotational acceleration, and road gradient as forces acting on vehicle.
Multicore Education through Simulation
ERIC Educational Resources Information Center
Ozturk, O.
2011-01-01
A project-oriented course for advanced undergraduate and graduate students is described for simulating multiple processor cores. Simics, a free simulator for academia, was utilized to enable students to explore computer architecture, operating systems, and hardware/software cosimulation. Motivation for including this course in the curriculum is…
Seamless Simulation Literature Survey
1992-04-01
completely. In addition, new work is going on all the time, so this survey will require updating. Projects such as CRONUS or CASES, for example, were excluded...BDS-D BFIT• BFRS CASES 9-2 CIT COMPREHENSIVE THEATER LEVEL SIMULATION CRONUS cTls DISTRIBUTED WARFIGHTING SIMULATION DWS DWSS EAGLE FAMSIM FBL FUTURE
ERIC Educational Resources Information Center
McCormick, Kathryn Eaton
1975-01-01
In keeping with current trends in career education in home economics, the food classes at Tuscola High School, Illinois, were involved in a bakery simulation. Objectives, suggestions for developing a simulated bakery, job roles, benefits, and sample forms are presented. (Author/MW)
ERIC Educational Resources Information Center
Ferrari, Pier Alda; Barbiero, Alessandro
2012-01-01
The increasing use of ordinal variables in different fields has led to the introduction of new statistical methods for their analysis. The performance of these methods needs to be investigated under a number of experimental conditions. Procedures to simulate from ordinal variables are then required. In this article, we deal with simulation from…
ERIC Educational Resources Information Center
Srinivasan, Srilekha; Perez, Lance C.; Palmer, Robert D.; Brooks, David W.; Wilson, Kathleen; Fowler, David
2006-01-01
A systematic study of the implementation of simulation hardware (TIMS) replacing software (MATLAB) was undertaken for advanced undergraduate and early graduate courses in electrical engineering. One outcome of the qualitative component of the study was remarkable: most students interviewed (4/4 and 6/9) perceived the software simulations as…
Simulating Laboratory Procedures.
ERIC Educational Resources Information Center
Baker, J. E.; And Others
1986-01-01
Describes the use of computer assisted instruction in a medical microbiology course. Presents examples of how computer assisted instruction can present case histories in which the laboratory procedures are simulated. Discusses an authoring system used to prepare computer simulations and provides one example of a case history dealing with fractured…
ERIC Educational Resources Information Center
Raymond, Chad; Usherwood, Simon
2013-01-01
Simulations are employed widely as teaching tools in political science, yet evidence of their pedagogical effectiveness, in comparison to other methods of instruction, is mixed. The assessment of learning outcomes is often a secondary concern in simulation design, and the qualitative and quantitative methods used to evaluate outcomes are…
NASA Technical Reports Server (NTRS)
Chapman, C. P.; Slusser, R. A.
1980-01-01
PARAMET, interactive simulation program for parametric studies of electric vehicles, guides user through simulation by menu and series of prompts for input parameters. Program considers aerodynamic drag, rolling resistance, linear and rotational acceleration, and road gradient as forces acting on vehicle.
Numerical Aerodynamic Simulation
NASA Technical Reports Server (NTRS)
1989-01-01
An overview of historical and current numerical aerodynamic simulation (NAS) is given. The capabilities and goals of the Numerical Aerodynamic Simulation Facility are outlined. Emphasis is given to numerical flow visualization and its applications to structural analysis of aircraft and spacecraft bodies. The uses of NAS in computational chemistry, engine design, and galactic evolution are mentioned.
ERIC Educational Resources Information Center
Srinivasan, Srilekha; Perez, Lance C.; Palmer, Robert D.; Brooks, David W.; Wilson, Kathleen; Fowler, David
2006-01-01
A systematic study of the implementation of simulation hardware (TIMS) replacing software (MATLAB) was undertaken for advanced undergraduate and early graduate courses in electrical engineering. One outcome of the qualitative component of the study was remarkable: most students interviewed (4/4 and 6/9) perceived the software simulations as…
NASA Technical Reports Server (NTRS)
Nicol, David; Fujimoto, Richard
1992-01-01
This paper surveys topics that presently define the state of the art in parallel simulation. Included in the tutorial are discussions on new protocols, mathematical performance analysis, time parallelism, hardware support for parallel simulation, load balancing algorithms, and dynamic memory management for optimistic synchronization.
Simulation. [SITE 2001 Section].
ERIC Educational Resources Information Center
Seymour, Cathy R., Ed.
This document contains three papers on simulation from the SITE (Society for Information Technology & Teacher Education) 2001 conference. "Simulations in the Learning Cycle: A Case Study Involving 'Exploring the Nardoo'" (William M. Dwyer and Valesca E. Lopez) presents a study of middle school students using a CD-based simulation…
Rehearsal Enabling Simulation Technologies
2011-03-01
developed by Renaissance Sciences Corporation (RSC) in collaboration with Elmendorf Civil Engineering, Joint Pacific Area Range Complex (JPARC) management...from the Air Force Combat Climatology Center (AFCCC) into Expert Common Immersive Theatre Environment (XCITE) threat simulations. AFCCC created an...L-3 Communications Link Simulation and Training, and Renaissance Science Corporation. The team provided as needed consultation to numerous
Radiation detector spectrum simulator
Wolf, M.A.; Crowell, J.M.
1985-04-09
A small battery operated nuclear spectrum simulator having a noise source generates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith to generate several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.
Radiation detector spectrum simulator
Wolf, Michael A.; Crowell, John M.
1987-01-01
A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.
Simulator Tests Controller Performance
NASA Technical Reports Server (NTRS)
Lembeck, M. F.; Rasmussen, R. D.
1986-01-01
Compact servosystem applies simulated dynamic loads, enabling realistic appraisal of motor and its control system without inconvenience of attaching real load. System simulates moments of inertia, rotational vibrations, changing load torques, and other characteristics of large or complex loads, without loads themselves and without awkwardness (and inaccuracy) of gravity-compensating devices used with such loads.
Political Simulations Using Excel
ERIC Educational Resources Information Center
Jackson, Steven F.
2013-01-01
Simulations have received considerable attention as a tool to promote problem-solving skills, intense involvement, and high-order thinking among students. Whether semester-long exercises or a single-class session, simulations are often used in areas of conflict studies, diplomatic studies, trade disputes, electoral processes, and policy and legal…
ERIC Educational Resources Information Center
Christy, Raymond M.
1975-01-01
Describes an unusual learning experience available to eighth-grade students in Louisiana through exposure to a World War II B-25 simulator. The flight simulator is used to motivate students in the science area, develop an awareness of flight problems and challenges and provide exposure to the electronics career field. (BR)
ERIC Educational Resources Information Center
Twelker, Paul A.
Simulation may be defined as (1) a technique of modeling (physically, iconically, verbally, or mathematically) some aspects of a real or proposed system, process, or environment or (2) the model (physical, iconic, verbal, or mathematical) of some aspects of a real or proposed system, process, or environment. Simulation may be used to generate…
Rainfall simulation in education
NASA Astrophysics Data System (ADS)
Peters, Piet; Baartman, Jantiene; Gooren, Harm; Keesstra, Saskia
2016-04-01
Rainfall simulation has become an important method for the assessment of soil erosion and soil hydrological processes. For students, rainfall simulation offers an year-round, attractive and active way of experiencing water erosion, while not being dependent on (outdoors) weather conditions. Moreover, using rainfall simulation devices, they can play around with different conditions, including rainfall duration, intensity, soil type, soil cover, soil and water conservation measures, etc. and evaluate their effect on erosion and sediment transport. Rainfall simulators differ in design and scale. At Wageningen University, both BSc and MSc student of the curriculum 'International Land and Water Management' work with different types of rainfall simulation devices in three courses: - A mini rainfall simulator (0.0625m2) is used in the BSc level course 'Introduction to Land Degradation and Remediation'. Groups of students take the mini rainfall simulator with them to a nearby field location and test it for different soil types, varying from clay to more sandy, slope angles and vegetation or litter cover. The groups decide among themselves which factors they want to test and they compare their results and discuss advantage and disadvantage of the mini-rainfall simulator. - A medium sized rainfall simulator (0.238 m2) is used in the MSc level course 'Sustainable Land and Water Management', which is a field practical in Eastern Spain. In this course, a group of students has to develop their own research project and design their field measurement campaign using the transportable rainfall simulator. - Wageningen University has its own large rainfall simulation laboratory, in which a 15 m2 rainfall simulation facility is available for research. In the BSc level course 'Land and Water Engineering' Student groups will build slopes in the rainfall simulator in specially prepared containers. Aim is to experience the behaviour of different soil types or slope angles when (heavy) rain
Trick Simulation Environment 07
NASA Technical Reports Server (NTRS)
Lin, Alexander S.; Penn, John M.
2012-01-01
The Trick Simulation Environment is a generic simulation toolkit used for constructing and running simulations. This release includes a Monte Carlo analysis simulation framework and a data analysis package. It produces all auto documentation in XML. Also, the software is capable of inserting a malfunction at any point during the simulation. Trick 07 adds variable server output options and error messaging and is capable of using and manipulating wide characters for international support. Wide character strings are available as a fundamental type for variables processed by Trick. A Trick Monte Carlo simulation uses a statistically generated, or predetermined, set of inputs to iteratively drive the simulation. Also, there is a framework in place for optimization and solution finding where developers may iteratively modify the inputs per run based on some analysis of the outputs. The data analysis package is capable of reading data from external simulation packages such as MATLAB and Octave, as well as the common comma-separated values (CSV) format used by Excel, without the use of external converters. The file formats for MATLAB and Octave were obtained from their documentation sets, and Trick maintains generic file readers for each format. XML tags store the fields in the Trick header comments. For header files, XML tags for structures and enumerations, and the members within are stored in the auto documentation. For source code files, XML tags for each function and the calling arguments are stored in the auto documentation. When a simulation is built, a top level XML file, which includes all of the header and source code XML auto documentation files, is created in the simulation directory. Trick 07 provides an XML to TeX converter. The converter reads in header and source code XML documentation files and converts the data to TeX labels and tables suitable for inclusion in TeX documents. A malfunction insertion capability allows users to override the value of any
NASA Technical Reports Server (NTRS)
1985-01-01
A Star Field Simulator has been developed to serve as a source of radiation for the ASTRO Star Tracker. The star tracker and simulator are components of a motion compensation test facility located at Marshall Space Flight Center in Huntsville, Alabama. Preflight tests and simulations using various levels of guide stars are performed in the test facility to establish performance of the motion compensation system before being used in a flight environment. The ASTRO Star Tracker operates over a wide dynamic range of irradiance corresponding to visual stellar magnitudes of -0.8 to 8. A minimum of three simulated guide stars with variable magnitudes are needed to fully test the Star Tracker performance under simulated mission conditions.
Educational science meets simulation.
Pasquale, Susan J
2015-03-01
With the increased use of simulation to teach the knowledge and skills demanded of clinical practice, toward the achievement of optimal patient care outcomes, it becomes increasingly important that clinician educators have fundamental knowledge about educational science and its applications to teaching and learning. As the foremost goal of teaching is to facilitate learning, it is essential that the simulation experience be oriented to the learning process. In order for this to occur, is it necessary for the clinician educator to understand the fundamentals of educational science and theories of education such that they can apply them to teaching and learning in an environment focused on medical simulation. Underscoring the rationale for the fundamentals of educational science to be applied to the simulation environment, and to work in tandem with simulation, is the importance that accurate and appropriate information is retained and applied toward establishing competence in essential practice-based skills and procedures. Copyright © 2015 Elsevier Ltd. All rights reserved.
Simulation in spinal diseases.
Aso Escario, José; Martínez Quiñones, José Vicente; Aso Vizán, Alberto; Arregui Calvo, Ricardo; Bernal Lafuente, Marta; Alcázar Crevillén, Andrés
2014-01-01
Simulation is frequent in spinal disease, resulting in problems for specialists like Orthopedic Surgeons, Neurosurgeons, Reumathologists, etc. Simulation requires demonstration of the intentional production of false or exaggerated symptoms following an external incentive. The clinician has difficulties in demonstrating these criteria, resulting in misdiagnosis of simulation or misinterpretation of the normal patient as a simulator, with the possibility of iatrogenic distress and litigation. We review simulation-related problems in spine, proposing a terminological, as well as a diagnostic strategy including clinical and complementary diagnosis, as a way to avoid misinterpretation and minimize the iatrogenic distress and liability Based on the clinical-Forensic author's expertise, the literature is analyzed and the terminology readdressed to develop new terms (inconsistences, incongruences, discrepancies and contradictions). Clinical semiology and complementary test are adapted to the new scenario. Diagnostic strategy relies on anamnesis, clinical and complementary tests, adapting them to a uniform terminology with clear meaning of signs and symptoms.
Kalvas, Taneli
2005-11-08
IBSimu(Ion Beam Simulator) is a computer program for making two and three dimensional ion optical simulations. The program can solve electrostatic field in a rectangular mesh using Poisson equation using Finite Difference method (FDM). The mesh can consist of a coarse and a fine part so that the calculation accuracy can be increased in critical areas of the geometry, while most of the calculation is done quickly using the coarse mesh. IBSimu can launch ion beam trajectories into the simulation from an injection surface or fomo plasma. Ion beam space charge of time independent simulations can be taken in account using Viasov iteration. Plasma is calculated by compensating space charge with electrons having Boltzmann energy distribution. The simulation software can also be used to calculate time dependent cases if the space charge is not calculated. Software includes diagnostic tools for plotting the geometry, electric field, space charge map, ion beam trajectories, emittance data and beam profiles.
Hardware Accelerated Simulated Radiography
Laney, D; Callahan, S; Max, N; Silva, C; Langer, S; Frank, R
2005-04-12
We present the application of hardware accelerated volume rendering algorithms to the simulation of radiographs as an aid to scientists designing experiments, validating simulation codes, and understanding experimental data. The techniques presented take advantage of 32 bit floating point texture capabilities to obtain validated solutions to the radiative transport equation for X-rays. An unsorted hexahedron projection algorithm is presented for curvilinear hexahedra that produces simulated radiographs in the absorption-only regime. A sorted tetrahedral projection algorithm is presented that simulates radiographs of emissive materials. We apply the tetrahedral projection algorithm to the simulation of experimental diagnostics for inertial confinement fusion experiments on a laser at the University of Rochester. We show that the hardware accelerated solution is faster than the current technique used by scientists.
Simulation Interoperability (Interoperabilite de la simulation)
2015-01-01
engineers and information specialists. In addition to providing critical technical oversight, they also provide a communication link to military... LINK systems Simulations of LinkX systems (Joint Tactical Information Distribution System – JTIDS) may not implement the LinkX communication protocol in...discussed along with the examples. Data Link and Physical Layer This layer deals with mechanical, electrical, optical and RF connections. Typical
Savara, Aditya
2016-08-15
The paper by Campbell et al. was recently brought to my attention. This comment is written to provide greater clarity to the community to prevent misconceptions regarding the entropies being discussed in that work and to clarify the differences between the adsorbate standard states suggested by Campbell and by Savara.
Savara, Aditya
2016-08-15
The paper by Campbell et al. was recently brought to my attention. This comment is written to provide greater clarity to the community to prevent misconceptions regarding the entropies being discussed in that work and to clarify the differences between the adsorbate standard states suggested by Campbell and by Savara.
Molecular dynamics simulations.
Lindahl, Erik
2015-01-01
Molecular dynamics has evolved from a niche method mainly applicable to model systems into a cornerstone in molecular biology. It provides us with a powerful toolbox that enables us to follow and understand structure and dynamics with extreme detail-literally on scales where individual atoms can be tracked. However, with great power comes great responsibility: Simulations will not magically provide valid results, but it requires a skilled researcher. This chapter introduces you to this, and makes you aware of some potential pitfalls. We focus on the two basic and most used methods; optimizing a structure with energy minimization and simulating motion with molecular dynamics. The statistical mechanics theory is covered briefly as well as limitations, for instance the lack of quantum effects and short timescales. As a practical example, we show each step of a simulation of a small protein, including examples of hardware and software, how to obtain a starting structure, immersing it in water, and choosing good simulation parameters. You will learn how to analyze simulations in terms of structure, fluctuations, geometrical features, and how to create ray-traced movies for presentations. With modern GPU acceleration, a desktop can perform μs-scale simulations of small proteins in a day-only 15 years ago this took months on the largest supercomputer in the world. As a final exercise, we show you how to set up, perform, and interpret such a folding simulation.
NASA Astrophysics Data System (ADS)
Fischetti, M. A.; Truxal, C.
1985-03-01
The present investigation is mainly concerned with simulators employed in the training of pilots in the Armed Services and other military personnel, taking into account certain problems and approaches for overcoming them. The use of simulators for training programs has a number of advantages compared to training involving a use of the actual equipment. Questions arise, however, regarding the value of such a training. Thus, it has been said that, while simulators gave students practice in manual skill, they could not teach them to handle the stress of being in a real aircraft. It has also been argued that some tasks are not represented accurately enough for proper training. In response to this criticism, the capacity of the simulators has been greatly improved. However, this development leads to problems related to the cost of simulator training. Attention is given to better visuals for flight simulators, the current generation of graphics imagery and expected improvements, possibilities for reducing flight simulator costs, and advances due to progress in microcomputers.
NASA Astrophysics Data System (ADS)
Moroz, Paul; Moroz, Daniel
2016-09-01
Plasma is an indispensable tool in materials processing. It provides chemically and physically active species and directional flows of energetic species enabling deep etching with good straight profiles required by the industry. At present time, the only feasible methods of simulating the resulting feature profiles are those which fall within the scope of feature-scale (FS) simulation methods, utilizing engineering-type of reactions of incoming species with solid materials. At the same time, the molecule dynamics (MD) methods are emerging as an important alternative approach to simulating extremely small features with sizes below of a few nanometers. In our presentation, we discuss both FS methods implemented into the FPS3D code and MD methods implemented into the MDSS code. We also discuss the ways of extracting information about the reactions and interactions used in FS codes from the MD simulations utilizing the approach of interatomic potentials. For this presentation, we selected two types of simulation cases for etching. The first type considers simulation of mostly etching and implantation, such as during Si etching by chlorine-argon plasma. The second type considers ALE (atomic layer etch) when etching is done by a cyclic process of surface passivation/activation with the following process of etching/removal of a single atomic layer per cycle or per a few cycles, allowing ultimate processing accuracy. The simulations are carried out with both FS and MD codes to provide the data for relation and comparison between those two very different approaches.
Interactive reservoir simulation
Regtien, J.M.M. Por, G.J.A.; Stiphout, M.T. van; Vlugt, F.F. van der
1995-12-31
Shell`s new Modular Reservoir Simulator (MoReS) has been equipped with a comprehensive and versatile user interface called FrontEnd. Apart from providing a user-friendly environment for interactive reservoir simulation, FrontEnd serves a software platform for other dynamic simulation and reservoir-engineering applications. It offers to all supported applications a common user interface, enables the re-use of code and reduces overall maintenance and support costs associated with the embedded applications. Because of its features, FrontEnd facilitates the transfer of research results in the form of operational software to end users. When coupled with MoReS, FrontEnd can be used for pre- and post-processing and interactive simulation. The pre-processing options allow data to be inputted by means of various OSF/Motif widgets containing a spreadsheet, text editors, dialogues and graphical input. The display of the input data as well as the post-processing of all simulation results is made possible by a variety of user-defined plot of tabular (e.g. timestep summary) and array (simulation grid) data. During a simulation user-defined plots can be displayed and edited, allowing a close inspection of the results as they are being calculated. FrontEnd has been equipped with a powerful input command language, which gives the batch user as much flexibility and control over the input as the interactive user.
NASA Astrophysics Data System (ADS)
di Candia, Roberto; Mejia, Bernabé; Castillo, Hernan; Simon Pedernales, Julen; Casanova, Jorge; Solano, Enrique
2014-03-01
We introduce the concept of embedding quantum simulator, a paradigm allowing efficient computation of dynamical quantities requiring full quantum tomography in a standard quantum simulator (one-to-one quantum simulator). The concept consists in the suitable encoding of a simulated quantum dynamics in the enlarged Hilbert space of an embedding quantum simulator. In this manner, non-trivial quantities are mapped onto physical observables, overcoming the necessity of full tomography, and reducing drastically the experimental requirements. As examples, we discuss how to evaluate entanglement monotones and time correlation functions, each in a suitable embedding quantum simulator. Finally, we expect that the proposed embedding framework paves the way for a general theory of enhanced one-to-one quantum simulators. This work is supported by Spanish MINECO FIS2012-36673-C03-02; UPV/EHU UFI 11/55; UPV/EHU PhD fellowship; Basque Government IT472-10; SOLID, CCQED, PROMISCE, SCALEQIT EU projects; and Marco Polo PUCP grant.
Byrne, Bobbi J; Manhas, Deepak
2016-11-01
Numerous factors contribute to neonatal morbidity and mortality, and inexperienced providers managing crisis situations is one major cause. Simulation-based medical education is an excellent modality to employ in community hospitals to help refine and refresh resuscitation skills of providers who infrequently encounter neonatal emergencies. Mounting evidence suggests that simulation-based education improves patient outcomes. Academic health centers have the potential to improve neonatal outcomes through collaborations with community hospital providers, sharing expertise in neonatal resuscitation and simulation. Community outreach programs using simulation have been successfully initiated in North America. Two examples of programs are described here, including the models for curricular development, required resources, limitations, and benefits. Considerations for initiating outreach simulation programs are discussed. In the future, research demonstrating improved neonatal outcomes using outreach simulation will be important for personnel conducting outreach programs. Neonatal outreach simulation is a promising educational endeavor that may ultimately prove important in decreasing neonatal morbidity and mortality. Copyright © 2016 Elsevier Inc. All rights reserved.
SOFIA tracking image simulation
NASA Astrophysics Data System (ADS)
Taylor, Charles R.; Gross, Michael A. K.
2016-09-01
The Stratospheric Observatory for Infrared Astronomy (SOFIA) tracking camera simulator is a component of the Telescope Assembly Simulator (TASim). TASim is a software simulation of the telescope optics, mounting, and control software. Currently in its fifth major version, TASim is relied upon for telescope operator training, mission planning and rehearsal, and mission control and science instrument software development and testing. TASim has recently been extended for hardware-in-the-loop operation in support of telescope and camera hardware development and control and tracking software improvements. All three SOFIA optical tracking cameras are simulated, including the Focal Plane Imager (FPI), which has recently been upgraded to the status of a science instrument that can be used on its own or in parallel with one of the seven infrared science instruments. The simulation includes tracking camera image simulation of starfields based on the UCAC4 catalog at real-time rates of 4-20 frames per second. For its role in training and planning, it is important for the tracker image simulation to provide images with a realistic appearance and response to changes in operating parameters. For its role in tracker software improvements, it is vital to have realistic signal and noise levels and precise star positions. The design of the software simulation for precise subpixel starfield rendering (including radial distortion), realistic point-spread function as a function of focus, tilt, and collimation, and streaking due to telescope motion will be described. The calibration of the simulation for light sensitivity, dark and bias signal, and noise will also be presented
NASA Technical Reports Server (NTRS)
Nakamura, Y.; Leonard, A.; Spalart, P. R.
1985-01-01
A vortex breakdown was simulated by the vortex filament method, and detailed figures are presented based on the results. Deformations of the vortex filaments showed clear and large swelling at a particular axial station which implied the presence of a recirculation bubble at that station. The tendency for two breakdowns to occur experimentally was confirmed by the simulation, and the jet flow inside the bubble was well simulated. The particle paths spiralled with expansion, and the streamlines took spiral forms at the breakdown with expansion.
Farrell, Joyce E; Catrysse, Peter B; Wandell, Brian A
2012-02-01
We describe a simulation of the complete image processing pipeline of a digital camera, beginning with a radiometric description of the scene captured by the camera and ending with a radiometric description of the image rendered on a display. We show that there is a good correspondence between measured and simulated sensor performance. Through the use of simulation, we can quantify the effects of individual digital camera components on system performance and image quality. This computational approach can be helpful for both camera design and image quality assessment.
Breathing metabolic simulator.
NASA Technical Reports Server (NTRS)
Bartlett, R. G., Jr.; Hendricks, C. M.; Morison, W. B.
1971-01-01
Description of a device for simulation of the human breathing and metabolic parameters required for the evaluation of respiratory diagnostic, monitoring, support and resuscitation equipment. The remotely controlled device allows wide variations in breathing rate and depth, breath velocity contour, oxygen uptake and carbon dioxide release to simulate conditions from sleep to hard work, with respiration exchange ratios ranging from hypoventilation to hyperventilation. It also reduces the cost of prolonged testing when simulation chambers with human subjects require three shifts of crews and standby physicians. Several block diagrams of the device and subsystems are given.
Carlos Serrano, Lawrence Doolittle
2015-10-29
GFS is a simulation engine that is used for the characterization of Accelerator performance parameters based on the machine layout, configuration and noise sources. It combines extensively tested Feedback models with a longitudinal phase space tracking simulator along with the interaction between the two via beam-based feedback using a computationally efficient simulation engine. The models include beam instrumentation, considerations on loop delays for in both the R and beam-based feedback loops, as well as the ability to inject noise (both correlated and uncorrelated) at different points of the machine including a full characterization of the electron gun performance parameters.
Structural mechanics simulations
NASA Technical Reports Server (NTRS)
Biffle, Johnny H.
1992-01-01
Sandia National Laboratory has a very broad structural capability. Work has been performed in support of reentry vehicles, nuclear reactor safety, weapons systems and components, nuclear waste transport, strategic petroleum reserve, nuclear waste storage, wind and solar energy, drilling technology, and submarine programs. The analysis environment contains both commercial and internally developed software. Included are mesh generation capabilities, structural simulation codes, and visual codes for examining simulation results. To effectively simulate a wide variety of physical phenomena, a large number of constitutive models have been developed.
Clark, Erin A S; Fisher, Janet; Arafeh, Julia; Druzin, Maurice
2010-03-01
Obstetrical emergencies require the rapid formation of a team with clear communication, strong leadership, and appropriate decision-making to ensure a positive patient outcome. Obstetric teams can improve their emergency response capability and efficiency through team and simulation training. Postpartum hemorrhage is an ideal model for team and simulation training, as postpartum hemorrhage requires a multidisciplinary team with the capability to produce a protocol-driven, rapid response. This article provides an overview of team and simulation training and focuses on applications within obstetrics, particularly preparation for postpartum hemorrhage.
NASA Astrophysics Data System (ADS)
Dulǎu, Lucian Ioan
2015-12-01
This paper describes the simulation of a microgrid system with storage technologies. The microgrid comprises 6 distributed generators (DGs), 3 loads and a 150 kW storage unit. The installed capacity of the generators is 1100 kW, while the total load demand is 900 kW. The simulation is performed by using a SCADA software, considering the power generation costs, the loads demand and the system's power losses. The generators access the system in order of their power generation cost. The simulation is performed for the entire day.
Solar Sail Spaceflight Simulation
NASA Technical Reports Server (NTRS)
Lisano, Michael; Evans, James; Ellis, Jordan; Schimmels, John; Roberts, Timothy; Rios-Reyes, Leonel; Scheeres, Daniel; Bladt, Jeff; Lawrence, Dale; Piggott, Scott
2007-01-01
The Solar Sail Spaceflight Simulation Software (S5) toolkit provides solar-sail designers with an integrated environment for designing optimal solar-sail trajectories, and then studying the attitude dynamics/control, navigation, and trajectory control/correction of sails during realistic mission simulations. Unique features include a high-fidelity solar radiation pressure model suitable for arbitrarily-shaped solar sails, a solar-sail trajectory optimizer, capability to develop solar-sail navigation filter simulations, solar-sail attitude control models, and solar-sail high-fidelity force models.
1982-06-30
potential (smooth curve ) and the potential from the field solve (rough curve ).There are 2048 simulation cells and 100,000 particle$. The magnetic field... curve is that obtained from the simulation test particles. An average over :was made of 100 grid cells about the given position. -6- r’ B. Alfvin Ion...AND SIMULATION - i - I January I to Jun~e 30, 1982 .. -.. :.- DOE. Contract DE,--TO3-76ET53064 -I,’,_ ONR Contract NOO014-).C-0578 =" "{DTIC ~ JUL 7
1983-05-24
S83-32571 (23 May 1983) --- Four-fifths of the STS-7 crew take a break from simulations in the Johnson Space Center?s Mission Simulation and Training Facility and pose for NASA photographer. Standing on the steps leading into the motion-based Shuttle Mission Simulator (SMS) are (left to right) astronauts Robert L. Crippen, John M. Fabian, Frederick H. Hauck and Sally K. Ride. Crippen is crew commander; Hauck, pilot; and Fabian and Ride are mission specialists, along with Norman E. Thagard (not involved in this phase of training and not pictured). Photo credit: NASA
Breathing metabolic simulator.
NASA Technical Reports Server (NTRS)
Bartlett, R. G., Jr.; Hendricks, C. M.; Morison, W. B.
1971-01-01
Description of a device for simulation of the human breathing and metabolic parameters required for the evaluation of respiratory diagnostic, monitoring, support and resuscitation equipment. The remotely controlled device allows wide variations in breathing rate and depth, breath velocity contour, oxygen uptake and carbon dioxide release to simulate conditions from sleep to hard work, with respiration exchange ratios ranging from hypoventilation to hyperventilation. It also reduces the cost of prolonged testing when simulation chambers with human subjects require three shifts of crews and standby physicians. Several block diagrams of the device and subsystems are given.
Computer-simulated phacoemulsification
NASA Astrophysics Data System (ADS)
Laurell, Carl-Gustaf; Nordh, Leif; Skarman, Eva; Andersson, Mats; Nordqvist, Per
2001-06-01
Phacoemulsification makes the cataract operation easier for the patient but involves a demanding technique for the surgeon. It is therefore important to increase the quality of surgical training in order to shorten the learning period for the beginner. This should diminish the risks of the patient. We are developing a computer-based simulator for training of phacoemulsification. The simulator is built on a platform that can be used as a basis for several different training simulators. A prototype has been made that has been partly tested by experienced surgeons.
Dynamical Simulation of Probabilities
NASA Technical Reports Server (NTRS)
Zak, Michail
1996-01-01
It has been demonstrated that classical probabilities, and in particular, probabilistic Turing machine, can be simulated by combining chaos and non-Lipschitz dynamics, without utilization of any man-made devices(such as random number generators). Self-orgainizing properties of systems coupling simulated and calculated probabilities and their link to quantum computations are discussed. Special attention was focused upon coupled stochastic processes, defined in terms of conditional probabilities, for which joint probability does not exist. Simulations of quantum probabilities are also discussed.
Simulation and Shoulder Dystocia.
Shaddeau, Angela K; Deering, Shad
2016-12-01
Shoulder dystocia is an unpredictable obstetric emergency that requires prompt interventions to ensure optimal outcomes. Proper technique is important but difficult to train given the urgent and critical clinical situation. Simulation training for shoulder dystocia allows providers at all levels to practice technical and teamwork skills in a no-risk environment. Programs utilizing simulation training for this emergency have consistently demonstrated improved performance both during practice drills and in actual patients with significantly decreased risks of fetal injury. Given the evidence, simulation training for shoulder dystocia should be conducted at all institutions that provide delivery services.
Dynamical Simulation of Probabilities
NASA Technical Reports Server (NTRS)
Zak, Michail
1996-01-01
It has been demonstrated that classical probabilities, and in particular, probabilistic Turing machine, can be simulated by combining chaos and non-Lipschitz dynamics, without utilization of any man-made devices(such as random number generators). Self-orgainizing properties of systems coupling simulated and calculated probabilities and their link to quantum computations are discussed. Special attention was focused upon coupled stochastic processes, defined in terms of conditional probabilities, for which joint probability does not exist. Simulations of quantum probabilities are also discussed.
Carlos Serrano, Lawrence Doolittle
2015-10-29
GFS is a simulation engine that is used for the characterization of Accelerator performance parameters based on the machine layout, configuration and noise sources. It combines extensively tested Feedback models with a longitudinal phase space tracking simulator along with the interaction between the two via beam-based feedback using a computationally efficient simulation engine. The models include beam instrumentation, considerations on loop delays for in both the R and beam-based feedback loops, as well as the ability to inject noise (both correlated and uncorrelated) at different points of the machine including a full characterization of the electron gun performance parameters.
Bioinspired swimming simulations
NASA Astrophysics Data System (ADS)
Bergmann, Michel; Iollo, Angelo
2016-10-01
We present a method to simulate the flow past bioinspired swimmers starting from pictures of an actual fish. The overall approach requires i) a skeleton graph generation to get a level-set function from pictures; ii) optimal transportation to obtain the velocity on the body surface; iii) flow simulations realized with a Cartesian method based on penalization. This technique can be used to automate modeling swimming motion from data collected by biologists. We illustrate this paradigm by simulating the swimming of a mackerel fish.
Distributed Simulation for Space Exploration
NASA Technical Reports Server (NTRS)
Crues, Edwin Z.
2006-01-01
This viewgraph presentation reviews the use of simulation and modeling in preparation for the planned exploration initiatives. The Exploration Systems Mission Directorate (EMSD) Integrated Modeling and Simulation (IM&S) team strategy encompasses a wide spectrum of simulation and modeling policies and technologies. One prominent technology is distributed simulation. The DIstributed Simulation (DIS),a collaborative simulation project with international participation (US and Japan) is reviewed as an example of distributed simulation development. The Distributed Space Exploration Simulation (DSES) is another example of distributed simulation that is described
... Stories Español Eye Health / Eye Health A-Z Cataracts Sections What Are Cataracts? Cataract Symptoms Who Is ... Pictures and Videos: What Do Cataracts Look Like? Cataract Vision Simulator Jun. 11, 2014 How do cataracts ...
Top, Philip; Woodward, Carol; Smith, Steve; Banks, Lawrence; Kelley, Brian
2015-09-14
GridDyn is a part of power grid simulation toolkit. The code is designed using modern object oriented C++ methods utilizing C++11 and recent Boost libraries to ensure compatibility with multiple operating systems and environments.
Water Quality Analysis Simulation
The Water Quality analysis simulation Program, an enhancement of the original WASP. This model helps users interpret and predict water quality responses to natural phenomena and man-made pollution for variious pollution management decisions.
Television Quiz Show Simulation
ERIC Educational Resources Information Center
Hill, Jonnie Lynn
2007-01-01
This article explores the simulation of four television quiz shows for students in China studying English as a foreign language (EFL). It discusses the adaptation and implementation of television quiz shows and how the students reacted to them.
Simulation of Gravitational Microlensing
This simulation shows the 22-year journey of a star moving through space and passing directly in front of a more distant background star. All stars drift through space. Occasionally, a star lines u...
NASA Technical Reports Server (NTRS)
Bartlett, R. G.; Hendricks, C. M.; Morison, W. B.
1972-01-01
The development of a breathing metabolic simulator (BMS) is reported. This BMS simulates all of the breathing and metabolic parameters required for complete evaluation and test of life support and resuscitation equipment. It is also useful for calibrating and validating mechanical and gaseous pulmonary function test procedures. Breathing rate, breathing depth, breath velocity contour, oxygen uptake, and carbon dioxide release are all variable over wide ranges simulating conditions from sleep to hard work with respiratory exchange ratios covering the range from hypoventilation. In addition, all of these parameters are remotely controllable to facilitate use of the device in hostile or remote environments. The exhaled breath is also maintained at body temperature and a high humidity. The simulation is accurate to the extent of having a variable functional residual capacity independent of other parameters.
Television Quiz Show Simulation
ERIC Educational Resources Information Center
Hill, Jonnie Lynn
2007-01-01
This article explores the simulation of four television quiz shows for students in China studying English as a foreign language (EFL). It discusses the adaptation and implementation of television quiz shows and how the students reacted to them.
... gov Site Map News Organization Search NWS All NOAA Home Why build an accessible web? How many ... Updates, additions Contact Us For assistance contact your NOAA Line Office Section 508 Coordinator Color blindness Simulations ...
Chemical Transformation Simulator
The Chemical Transformation Simulator (CTS) is a web-based, high-throughput screening tool that automates the calculation and collection of physicochemical properties for an organic chemical of interest and its predicted products resulting from transformations in environmental sy...
ERIC Educational Resources Information Center
Rouse, Michael W.; And Others
1988-01-01
A simulation of the decreased visual acuity of individuals with amblyopia is used in one optometry program to help students understand how amblyopia patients see. Students act as patient, then as doctor, proceeding through clinical diagnosis. (MSE)
A TGF produces gamma rays (magenta) as well as high-energy electrons (yellow) and positrons (green). This simulation tracks a TGF and its particle beams from their origin altitude of 9.3 miles (15 ...
Compressible Astrophysics Simulation Code
Howell, L.; Singer, M.
2007-07-18
This is an astrophysics simulation code involving a radiation diffusion module developed at LLNL coupled to compressible hydrodynamics and adaptive mesh infrastructure developed at LBNL. One intended application is to neutrino diffusion in core collapse supernovae.
Gemini Rendezvous Docking Simulator
NASA Technical Reports Server (NTRS)
1964-01-01
Gemini Rendezvous Docking Simulator suspended from the roof of the Langley Research Center's aircraft hanger. Francis B. Smith wrote: 'The rendezvous and docking operation of the Gemini spacecraft with the Agena and of the Apollo Command Module with the Lunar Excursion Module have been the subject of simulator studies for several years. [This figure] illustrates the Gemini-Agena rendezvous docking simulator at Langley. The Gemini spacecraft was supported in a gimbal system by an overhead crane and gantry arrangement which provided 6 degrees of freedom - roll, pitch, yaw, and translation in any direction - all controllable by the astronaut in the spacecraft. Here again the controls fed into a computer which in turn provided an input to the servos driving the spacecraft so that it responded to control motions in a manner which accurately simulated the Gemini spacecraft.'
2015-04-14
This collage of NASA Cassini spacecraft images and computer simulations shows how long, sinuous features from Enceladus can be modeled by tracing the trajectories of tiny, icy grains ejected from the moon south polar geysers.
Strachan, J.D.; Roberts, J.A.
1989-09-01
The LOCUS data base program has been used to simulate images and to solve simple equations. This has been accomplished by making each record (which normally would represent a data entry)represent sequenced or random number pairs.
Software engineering and simulation
NASA Technical Reports Server (NTRS)
Zhang, Shou X.; Schroer, Bernard J.; Messimer, Sherri L.; Tseng, Fan T.
1990-01-01
This paper summarizes the development of several automatic programming systems for discrete event simulation. Emphasis is given on the model development, or problem definition, and the model writing phases of the modeling life cycle.
Rocket engine numerical simulator
NASA Technical Reports Server (NTRS)
Davidian, Ken
1993-01-01
The topics are presented in viewgraph form and include the following: a rocket engine numerical simulator (RENS) definition; objectives; justification; approach; potential applications; potential users; RENS work flowchart; RENS prototype; and conclusion.
Rocket engine numerical simulation
NASA Technical Reports Server (NTRS)
Davidian, Ken
1993-01-01
The topics are presented in view graph form and include the following: a definition of the rocket engine numerical simulator (RENS); objectives; justification; approach; potential applications; potential users; RENS work flowchart; RENS prototype; and conclusions.
Physics and Detector Simulations
Graf, N.
2004-10-11
The simulation tools session was divided into three main areas of concentration: physics event simulation and event generators, full detector simulation and event reconstruction frameworks, and fast simulation and physics analysis frameworks. Although the primary purpose of the plenary session talk was to summarize the contents of the parallel session presentations for those unable to attend, the intent of this write-up is to attempt to point out features in common among the ongoing efforts and present a personal view of some goals for the future. The reader is directed to the individual write-ups for details on the specific topics discussed during the workshop. A brief summary and synthesis of topics presented during the tools parallel sessions.
1991-05-01
14 Track ............. ............................................ 15 Cities ............. ............................................ 16 4.2...23 Cities ............ ............................................ 24 5.3 Simulated Agents...Conditions 43 E Commands 43 E.1 General Commands .......... ..................................... 43 E.2 City Commands
NASA Astrophysics Data System (ADS)
Abdel-Khalik, Hany Samy
The work presented in this thesis is a continuation of a master's thesis research project conducted by the author to gain insight into the applicability of inverse methods to developing adaptive simulation capabilities for core physics problems. Use of adaptive simulation is intended to improve the fidelity and robustness of important core attributes predictions such as core power distribution, thermal margins and core reactivity. Adaptive simulation utilizes a selected set of past and current reactor measurements of reactor observables, i.e. in-core instrumentations readings, to adapt the simulation in a meaningful way. A meaningful adaption will result in high fidelity and robust adapted core simulators models. To perform adaption, we propose an inverse theory approach in which the multitudes of input data to core simulators, i.e. reactor physics and thermal-hydraulic data, are to be adjusted to improve agreement with measured observables while keeping core simulators models unadapted. At a first glance, devising such adaption for typical core simulators models would render the approach impractical. This follows, since core simulators are based on very demanding computational models, i.e. based on complex physics models with millions of input data and output observables. This would spawn not only several prohibitive challenges but also numerous disparaging concerns. The challenges include the computational burdens of the sensitivity-type calculations required to construct Jacobian operators for the core simulators models. Also, the computational burdens of the uncertainty-type calculations required to estimate the uncertainty information of core simulators input data presents a demanding challenge. The concerns however are mainly related to the reliability of the adjusted input data. We demonstrate that the power of our proposed approach is mainly driven by taking advantage of this unfavorable situation. Our contribution begins with the realization that to obtain
Chemical Transformation Simulator
The Chemical Transformation Simulator (CTS) is a web-based, high-throughput screening tool that automates the calculation and collection of physicochemical properties for an organic chemical of interest and its predicted products resulting from transformations in environmental sy...
Electromechanical simulations of dislocations
NASA Astrophysics Data System (ADS)
Skiba, Oxana; Gracie, Robert; Potapenko, Stanislav
2013-04-01
Improving the reliability of micro-electronic devices depends in part on developing a more in-depth understanding of dislocations because dislocations are barriers to charge carriers. To this end, the quasi-static simulation of discrete dislocations dynamics in materials under mechanical and electrical loads is presented. The simulations are based on the extended finite element method, where dislocations are modelled as internal discontinuities. The strong and weak forms of the boundary value problem for the coupled system are presented. The computation of the Peach-Koehler force using the J-integral is discussed. Examples to illustrate the accuracy of the simulations are presented. The motion of the network of the dislocations under different electrical and mechanical loads is simulated. It was shown that even in weak piezoelectric materials the effect of the electric field on plastic behaviour is significant.
Xyce parallel electronic simulator.
Keiter, Eric R; Mei, Ting; Russo, Thomas V.; Rankin, Eric Lamont; Schiek, Richard Louis; Thornquist, Heidi K.; Fixel, Deborah A.; Coffey, Todd S; Pawlowski, Roger P; Santarelli, Keith R.
2010-05-01
This document is a reference guide to the Xyce Parallel Electronic Simulator, and is a companion document to the Xyce Users Guide. The focus of this document is (to the extent possible) exhaustively list device parameters, solver options, parser options, and other usage details of Xyce. This document is not intended to be a tutorial. Users who are new to circuit simulation are better served by the Xyce Users Guide.
Geothermal reservoir simulation
NASA Technical Reports Server (NTRS)
Mercer, J. W., Jr.; Faust, C.; Pinder, G. F.
1974-01-01
The prediction of long-term geothermal reservoir performance and the environmental impact of exploiting this resource are two important problems associated with the utilization of geothermal energy for power production. Our research effort addresses these problems through numerical simulation. Computer codes based on the solution of partial-differential equations using finite-element techniques are being prepared to simulate multiphase energy transport, energy transport in fractured porous reservoirs, well bore phenomena, and subsidence.
1992-03-01
MacPherson USN utilized the network capabilities of the Ong simulator to visually compare hierarchical and subsumption software architectures for AUV...Speed can be increased and graphics pipeline loading reduced through simplified object geometry , simplification of lighting models, simulator source code...as possible in order to allow increasingly sophisticated analysis of data. A formal geometry -based approach also permits expert system compatibility
Simulator manufacturers' requirements
NASA Technical Reports Server (NTRS)
Reilly, David R.
1987-01-01
Simulator manufacturers must continue to provide the customers the latest wind shear models available for pilot training. The release of the JAWS data package enabled the provision of a much more realistic wind shear package to the customer rather than just the standard six SRI wind shear profiles currently in use. In this brief presentation, the steps taken in implementing the JAWS data into the FAA 727 simulator are highlighted.
Theory Modeling and Simulation
Shlachter, Jack
2012-08-23
Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.
Sinha, S.K.; Madia, J.; Dixon, S.
1995-11-01
The Consolidated Edison Company of New York, Inc. (Con Edison) has constructed a first-of-a-kind water hammer events simulator for use at its training center. The Learning Center, Con Edison`s central training facility, intends to use the simulator as an educational tool to demonstrate the various mechanisms of the water hammer phenomenon to power plant designers, engineers and operators. The water hammer phenomenon has been studied extensively for the past 15 years for the nuclear industry. However, the acknowledge of the various water hammer mechanisms and the measures to prevent or mitigate water hammer have not been widely disseminated among the operators of fossil-fueled power plants. Con Edison personnel who operate the various generation stations and the New York City steam distribution systems are expected to benefit from the new simulator. Knowledge gained from interacting with the simulator will be very important in helping the Con Edison prevent, mitigate, or accommodate water hammer at its facilities. The water hammer simulator was fabricated in Con Edison`s central machine shop. Details of the design and construction of the simulator were finalized in consultation with Creare, Inc., an engineering research firm, located in Hanover, New Hampshire. The simulator seeks to recreate the essential features of water hammer in steam mines following the buildup of cold (subcooled) water by condensation and steam-water interaction. This paper describes the fabrication, design, testing, and operation of the Con Edison water hammer simulator. A discussion of how Con Edison plans to use the facility at The Learning Center is included.
Optimization Of Simulated Trajectories
NASA Technical Reports Server (NTRS)
Brauer, Garry L.; Olson, David W.; Stevenson, Robert
1989-01-01
Program To Optimize Simulated Trajectories (POST) provides ability to target and optimize trajectories of point-mass powered or unpowered vehicle operating at or near rotating planet. Used successfully to solve wide variety of problems in mechanics of atmospheric flight and transfer between orbits. Generality of program demonstrated by its capability to simulate up to 900 distinct trajectory phases, including generalized models of planets and vehicles. VAX version written in FORTRAN 77 and CDC version in FORTRAN V.
ANS Based Submarine Simulation
1994-08-01
computer based simulation proraon supplied by Dr. John Ware at Computer Sceinces Corporation (CSC). Thee am two reasons to use simulated data instead...ANS (Artificial Neural System) capable of modeling submarine perfomncie based on full scale data generated using a computer based simulabon program...The Optimized Entropy algorilth enables the solutions to diffcu problems on a desktop computer within an acceptable time frame. Ob6ectve for w
Simulators and Enhanced Training
1992-04-01
realistic for the particular tasks to be trained. Secondly, the relation of cost to realism is neither linear nor the same for different tasks. Figure...time spent training on a simulation. An algebraic I representation of this ratio is (Awo - Aw’)/S, where Awo is the training time in the actual... Friedberg , Schweinfurt, and Fulda. The Fort Knox site is currently the largest SIMNET facility with simulators for 44 M1 Abrams tanks, 28 M2/3 Bradley
2016-11-18
NASA Glenn's new LED solar simulator was developed by Angstrom Designs and UC Santa Barbara under a Small Business Innovative Research program to test the next generation of high-efficiency space solar cells for future missions. The new simulator contains over 1500 individually adjustable light sources, most of which emit light invisible to the human eye, to cover a 10 x10 foot area.
2016-11-16
NASA Glenn's new LED solar simulator was developed by Angstrom Designs and UC Santa Barbara under a Small Business Innovative Research program to test the next generation of high-efficiency space solar cells for future missions. The new simulator contains over 1500 individually adjustable light sources, most of which emit light invisible to the human eye, to cover a 10 x10 foot area.
NASA Technical Reports Server (NTRS)
1964-01-01
Multiple exposure of Rendezvous Docking Simulator. The Gemini spacecraft was supported in a gimbal system by an overhead crane and gantry arrangement which provided 6 degrees of freedom - roll, pitch, yaw, and translation in any direction - all controllable by the astronaut in the spacecraft. The controls fed into a computer which in turn provided an input to the servos driving the spacecraft so that it responded to control motions in a manner which accurately simulated the Gemini spacecraft.
2015-02-02
CHRISTOPHER CRUMBLY, MANAGER OF THE SPACECRAFT PAYLOAD INTEGRATION AND EVOLUTION OFFICE, GAVE VISITORS AN INSIDER'S PERSPECTIVE ON THE CORE STAGE SIMULATOR AT MARSHALL AND ITS IMPORTANCE TO DEVELOPMENT OF THE SPACE LAUNCH SYSTEM. CHRISTOPHER CRUMBLY, MANAGER OF THE SPACECRAFT PAYLOAD INTEGRATION AND EVOLUTION OFFICE, GAVE VISITORS AN INSIDER'S PERSPECTIVE ON THE CORE STAGE SIMULATOR AT MARSHALL AND ITS IMPORTANCE TO DEVELOPMENT OF THE SPACE LAUNCH SYSTEM.
Generic Distributed Simulation Architecture
Booker, C.P.
1999-05-14
A Generic Distributed Simulation Architecture is described that allows a simulation to be automatically distributed over a heterogeneous network of computers and executed with very little human direction. A prototype Framework is presented that implements the elements of the Architecture and demonstrates the feasibility of the concepts. It provides a basis for a future, improved Framework that will support legacy models. Because the Framework is implemented in Java, it may be installed on almost any modern computer system.
Artillery Engagement Simulation
1980-05-01
normally are conveyed to appropriate military agencies by briefing or Disposition Form. kS iv FOREWORD Current Army Training and Evaluation Programs (ARTEP...ENGAGEMENT SIMULATION BRIEF Requirement: To develop and evaluate a method for incorporating the field artillery battery into engagement simulation (ES...assisted by two E-3 drivers. Both were proficient in their MOS. To check the accuracy of the firemarkers, a flash base of three observation posts and a
Intelligently interactive combat simulation
NASA Astrophysics Data System (ADS)
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.
NASA Technical Reports Server (NTRS)
Simon, R. A.
1986-01-01
Electrical properties of solenoids imitated for tests of control circuits. Simulation circuit imitates voltage and current responses of two engine-controlling solenoids. Used in tests of programs of digital engine-control circuits, also provides electronic interface with circuits imitating electrical properties of pressure sensors and linear variable-differential transformers. Produces voltages, currents, delays, and discrete turnon and turnoff signals representing operation of solenoid in engine-control relay. Many such circuits used simulating overall engine circuitry.
Accelerator simulation using computers
Lee, M.; Zambre, Y.; Corbett, W.
1992-01-01
Every accelerator or storage ring system consists of a charged particle beam propagating through a beam line. Although a number of computer programs exits that simulate the propagation of a beam in a given beam line, only a few provide the capabilities for designing, commissioning and operating the beam line. This paper shows how a multi-track'' simulation and analysis code can be used for these applications.
Accelerator simulation using computers
Lee, M.; Zambre, Y.; Corbett, W.
1992-01-01
Every accelerator or storage ring system consists of a charged particle beam propagating through a beam line. Although a number of computer programs exits that simulate the propagation of a beam in a given beam line, only a few provide the capabilities for designing, commissioning and operating the beam line. This paper shows how a ``multi-track`` simulation and analysis code can be used for these applications.
NASA Technical Reports Server (NTRS)
Pisaich, Gregory; Flueckiger, Lorenzo; Neukom, Christian; Wagner, Mike; Buchanan, Eric; Plice, Laura
2007-01-01
The Mission Simulation Toolkit (MST) is a flexible software system for autonomy research. It was developed as part of the Mission Simulation Facility (MSF) project that was started in 2001 to facilitate the development of autonomous planetary robotic missions. Autonomy is a key enabling factor for robotic exploration. There has been a large gap between autonomy software (at the research level), and software that is ready for insertion into near-term space missions. The MST bridges this gap by providing a simulation framework and a suite of tools for supporting research and maturation of autonomy. MST uses a distributed framework based on the High Level Architecture (HLA) standard. A key feature of the MST framework is the ability to plug in new models to replace existing ones with the same services. This enables significant simulation flexibility, particularly the mixing and control of fidelity level. In addition, the MST provides automatic code generation from robot interfaces defined with the Unified Modeling Language (UML), methods for maintaining synchronization across distributed simulation systems, XML-based robot description, and an environment server. Finally, the MSF supports a number of third-party products including dynamic models and terrain databases. Although the communication objects and some of the simulation components that are provided with this toolkit are specifically designed for terrestrial surface rovers, the MST can be applied to any other domain, such as aerial, aquatic, or space.
NASA Astrophysics Data System (ADS)
Bauleo, P.; Bonifazi, C.; Filevich, A.
The angular and energy resolution of the TANGO Array has been obtained using Monte Carlo simulations. The AIRES code, with the SYBILL hadronic collision package, was used to simulate Extended Air Showers produced by primary cosmic rays (protons and iron nuclei), with energies ranging from 1014 eV to 1018 eV. These data were fed into a realistic code which simulates the response of the detector stations (water ˇCerenkov detectors), including the electronics, pick up noise, and the signal attenuation in the connecting cabling. The trigger stage is taken into account in order to produce estimates of the trigger efficiency of the array and to check the accuracy of the reconstruction codes. This paper describes the simulations performed to obtain the expected behavior of the array, and presents the simulated data. These simulations indicate that the accuracy of the cosmic ray primary energy determination is expected to be ˜ 60 % and the precision in the measurement of the direction of arrival can be estimated as ˜ 4 degrees.
NASA Astrophysics Data System (ADS)
Sorce, J. G.
2016-12-01
In the local Universe, cosmic structures can be observed down to very small scales, scales on which the standard cosmological model might fail. Such detailed observations have to be compared with simulations in order to verify the predictions of different cosmological models. However, the cosmic variance can obscure the tests. More precisely, comparisons on a one-to-one basis are feasible only with simulations that look like the local Universe. Constrained by observed positions and peculiar velocities of galaxies, the simulations presented here reproduce locally the three-dimensional distribution of matter. Within a sphere of radius 100 hMpc, the observed nearby Large and Small Scale Structure is simulated with an accuracy of a few megaparsecs. These simulations include our nearest cluster neighbor, Virgo, allowing a detailed study of its formation history. It follows that the Virgo cluster has had a quiet merging history within the last seven gigayears. In the near future, zoom-in hydrodynamical simulations of the later will permit deeper comparisons with observations.
Simulation of turbulent wall pressure
NASA Technical Reports Server (NTRS)
Ash, R. L.
1976-01-01
A computer program has been developed to simulate the transient wall pressure field produced by a low speed fully turbulent boundary layer. The theoretical basis for the simulation has been discussed and preliminary results from a pressure simulation are presented.
Converting DYNAMO simulations to Powersim Studio simulations
Walker, La Tonya Nicole; Malczynski, Leonard A.
2014-02-01
DYNAMO is a computer program for building and running 'continuous' simulation models. It was developed by the Industrial Dynamics Group at the Massachusetts Institute of Technology for simulating dynamic feedback models of business, economic, and social systems. The history of the system dynamics method since 1957 includes many classic models built in DYANMO. It was not until the late 1980s that software was built to take advantage of the rise of personal computers and graphical user interfaces that DYNAMO was supplanted. There is much learning and insight to be gained from examining the DYANMO models and their accompanying research papers. We believe that it is a worthwhile exercise to convert DYNAMO models to more recent software packages. We have made an attempt to make it easier to turn these models into a more current system dynamics software language, Powersim © Studio produced by Powersim AS^{2} of Bergen, Norway. This guide shows how to convert DYNAMO syntax into Studio syntax.
NASA Astrophysics Data System (ADS)
Suksila, Thada
Since its invention at the University of Stuttgart, Germany in the mid-1960, scientists have been trying to understand and explain the mechanism of the plasma interaction inside the magnetoplasmadynamics (MPD) thruster. Because this thruster creates a larger level of efficiency than combustion thrusters, this MPD thruster is the primary cadidate thruster for a long duration (planetary) spacecraft. However, the complexity of this thruster make it difficult to fully understand the plasma interaction in an MPD thruster while operating the device. That is, there is a great deal of physics involved: the fluid dynamics, the electromagnetics, the plasma dynamics, and the thermodynamics. All of these physics must be included when an MPD thruster operates. In recent years, a computer simulation helped scientists to simulate the experiments by programing the physics theories and comparing the simulation results with the experimental data. Many MPD thruster simulations have been conducted: E. Niewood et al.[5], C. K. J. Hulston et al.[6], K. D. Goodfellow[3], J Rossignol et al.[7]. All of these MPD computer simulations helped the scientists to see how quickly the system responds to the new design parameters. For this work, a 1D MPD thruster simulation was developed to find the voltage drop between the cathode and the plasma regions. Also, the properties such as thermal conductivity, electrical conductivity and heat capacity are temperature and pressure dependent. These two conductivity and heat capacity are usually definded as constant values in many other models. However, this 1D and 2D cylindrical symmetry MPD thruster simulations include both temperature and pressure effects to the electrical, thermal conductivities and heat capacity values interpolated from W. F. Ahtye [4]. Eventhough, the pressure effect is also significant; however, in this study the pressure at 66 Pa was set as a baseline. The 1D MPD thruster simulation includes the sheath region, which is the
Reduced Gravity Walking Simulator
NASA Technical Reports Server (NTRS)
1963-01-01
A test subject being suited up for studies on the Reduced Gravity Walking Simulator located in the hanger at Langley Research Center. The initial version of this simulator was located inside the hanger. Later a larger version would be located at the Lunar Landing Facility. The purpose of this simulator was to study the subject while walking, jumping or running. Researchers conducted studies of various factors such as fatigue limit, energy expenditure, and speed of locomotion. Francis B. Smith wrote in his paper 'Simulators For Manned Space Research,' 'I would like to conclude this talk with a discussion of a device for simulating lunar gravity which is very effective and yet which is so simple that its cost is in the order of a few thousand dollars at most, rather than hundreds of thousands. With a little ingenuity, one could almost build this type simulator in his backyard for children to play on. The principle is ...if a test subject is suspended in a sling so that his body axis makes an angle of 9 1/2 degrees with the horizontal and if he then 'stands' on a platform perpendicular to his body axis, the component of the earth's gravity forcing him toward the platform is one times the sine of 9 1/2 degrees or approximately 1/6 of the earth's normal gravity field. That is, a 180 pound astronaut 'standing' on the platform would exert a force of only 30 pounds - the same as if he were standing upright on the lunar surface.' Published in James R. Hansen, Spaceflight Revolution: NASA Langley Research Center From Sputnik to Apollo, NASA SP-4308; Francis B. Smith, 'Simulators For Manned Space Research,' Paper for 1966 IEEE International Convention, New York, NY, March 21-25, 1966.
EMU Suit Performance Simulation
NASA Technical Reports Server (NTRS)
Cowley, Matthew S.; Benson, Elizabeth; Harvill, Lauren; Rajulu, Sudhakar
2014-01-01
Introduction: Designing a planetary suit is very complex and often requires difficult trade-offs between performance, cost, mass, and system complexity. To verify that new suit designs meet requirements, full prototypes must be built and tested with human subjects. However, numerous design iterations will occur before the hardware meets those requirements. Traditional draw-prototype-test paradigms for research and development are prohibitively expensive with today's shrinking Government budgets. Personnel at NASA are developing modern simulation techniques that focus on a human-centric design paradigm. These new techniques make use of virtual prototype simulations and fully adjustable physical prototypes of suit hardware. This is extremely advantageous and enables comprehensive design down-selections to be made early in the design process. Objectives: The primary objective was to test modern simulation techniques for evaluating the human performance component of two EMU suit concepts, pivoted and planar style hard upper torso (HUT). Methods: This project simulated variations in EVA suit shoulder joint design and subject anthropometry and then measured the differences in shoulder mobility caused by the modifications. These estimations were compared to human-in-the-loop test data gathered during past suited testing using four subjects (two large males, two small females). Results: Results demonstrated that EVA suit modeling and simulation are feasible design tools for evaluating and optimizing suit design based on simulated performance. The suit simulation model was found to be advantageous in its ability to visually represent complex motions and volumetric reach zones in three dimensions, giving designers a faster and deeper comprehension of suit component performance vs. human performance. Suit models were able to discern differing movement capabilities between EMU HUT configurations, generic suit fit concerns, and specific suit fit concerns for crewmembers based
Videodisc Simulation: Tomorrow's Technology Today.
ERIC Educational Resources Information Center
Young, Jon I.
1984-01-01
Describes the positive features, significant benefits, and learner interaction modes of videodisc simulation technology and discusses the development of a program structure which utilizes videodisc simulation. (MBR)
Videodisc Simulation: Tomorrow's Technology Today.
ERIC Educational Resources Information Center
Young, Jon I.
1984-01-01
Describes the positive features, significant benefits, and learner interaction modes of videodisc simulation technology and discusses the development of a program structure which utilizes videodisc simulation. (MBR)
Training using medical simulation.
Grant, David J; Marriage, Stephen C
2012-03-01
As the time available for medical education is shortened by reductions in training hours and the demands of modern healthcare delivery, educators are increasingly looking towards simulation as a means of providing safe and reproducible situations for clinical skills teaching, decision-making and team training. The tools available for simulation-based training have developed rapidly over the past 15 years. There is an increasing range of manikins and part-task trainers - devices that permit selected elements of a skill or task to be practised independently of a whole-body manikin. Those interested in simulation have also focused significantly on adult learning theory to ensure that the training offered through simulation is appropriate, effective and complementary to other educational approaches. By mapping simulated scenarios to the Royal College of Paediatrics and Child Health Curriculum for General Paediatric Training at Level 1, the authors have developed two complementary courses aimed at preparing the general paediatric trainee for progression to the middle grade role. It is hoped that such approaches will become integral to paediatric training in the future.
NASA Technical Reports Server (NTRS)
Tikidjian, Raffi; Mackey, Ryan
2008-01-01
The DSN Array Simulator (wherein 'DSN' signifies NASA's Deep Space Network) is an updated version of software previously denoted the DSN Receive Array Technology Assessment Simulation. This software (see figure) is used for computational modeling of a proposed DSN facility comprising user-defined arrays of antennas and transmitting and receiving equipment for microwave communication with spacecraft on interplanetary missions. The simulation includes variations in spacecraft tracked and communication demand changes for up to several decades of future operation. Such modeling is performed to estimate facility performance, evaluate requirements that govern facility design, and evaluate proposed improvements in hardware and/or software. The updated version of this software affords enhanced capability for characterizing facility performance against user-defined mission sets. The software includes a Monte Carlo simulation component that enables rapid generation of key mission-set metrics (e.g., numbers of links, data rates, and date volumes), and statistical distributions thereof as functions of time. The updated version also offers expanded capability for mixed-asset network modeling--for example, for running scenarios that involve user-definable mixtures of antennas having different diameters (in contradistinction to a fixed number of antennas having the same fixed diameter). The improved version also affords greater simulation fidelity, sufficient for validation by comparison with actual DSN operations and analytically predictable performance metrics.
QTLMAS 2009: simulated dataset
2010-01-01
Background The simulation of the data for the QTLMAS 2009 Workshop is described. Objective was to simulate observations from a growth curve which was influenced by a number of QTL. Results The data consisted of markers, phenotypes and pedigree. Genotypes of 453 markers, distributed over 5 chromosomes of 1 Morgan each, were simulated for 2,025 individuals. From those, 25 individuals were parents of the other 2,000 individuals. The 25 parents were genetically related. Phenotypes were simulated according to a logistic growth curve and were made available for 1,000 of the 2,000 offspring individuals. The logistic growth curve was specified by three parameters. Each parameter was influenced by six Quantitative Trait Loci (QTL), positioned at the five chromosomes. For each parameter, one QTL had a large effect and five QTL had small effects. Variance of large QTL was five times the variance of small QTL. Simulated data was made available at http://www.qtlmas2009.wur.nl/UK/Dataset/. PMID:20380757
NASA Technical Reports Server (NTRS)
Phillips, Dave; Haas, William; Barth, Tim; Benjamin, Perakath; Graul, Michael; Bagatourova, Olga
2005-01-01
Range Process Simulation Tool (RPST) is a computer program that assists managers in rapidly predicting and quantitatively assessing the operational effects of proposed technological additions to, and/or upgrades of, complex facilities and engineering systems such as the Eastern Test Range. Originally designed for application to space transportation systems, RPST is also suitable for assessing effects of proposed changes in industrial facilities and large organizations. RPST follows a model-based approach that includes finite-capacity schedule analysis and discrete-event process simulation. A component-based, scalable, open architecture makes RPST easily and rapidly tailorable for diverse applications. Specific RPST functions include: (1) definition of analysis objectives and performance metrics; (2) selection of process templates from a processtemplate library; (3) configuration of process models for detailed simulation and schedule analysis; (4) design of operations- analysis experiments; (5) schedule and simulation-based process analysis; and (6) optimization of performance by use of genetic algorithms and simulated annealing. The main benefits afforded by RPST are provision of information that can be used to reduce costs of operation and maintenance, and the capability for affordable, accurate, and reliable prediction and exploration of the consequences of many alternative proposed decisions.
Multilevel turbulence simulations
Tziperman, E.
1994-12-31
The authors propose a novel method for the simulation of turbulent flows, that is motivated by and based on the Multigrid (MG) formalism. The method, called Multilevel Turbulence Simulations (MTS), is potentially more efficient and more accurate than LES. In many physical problems one is interested in the effects of the small scales on the larger ones, or in a typical realization of the flow, and not in the detailed time history of each small scale feature. MTS takes advantage of the fact that the detailed simulation of small scales is not needed at all times, in order to make the calculation significantly more efficient, while accurately accounting for the effects of the small scales on the larger scale of interest. In MTS, models of several resolutions are used to represent the turbulent flow. The model equations in each coarse level incorporate a closure term roughly corresponding to the tau correction in the MG formalism that accounts for the effects of the unresolvable scales on that grid. The finer resolution grids are used only a small portion of the simulation time in order to evaluate the closure terms for the coarser grids, while the coarse resolution grids are then used to accurately and efficiently calculate the evolution of the larger scales. The methods efficiency relative to direct simulations is of the order of the ratio of required integration time to the smallest eddies turnover time, potentially resulting in orders of magnitude improvement for a large class of turbulence problems.
NASA Technical Reports Server (NTRS)
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.
Molecular dynamics simulations.
Lindahl, Erik R
2008-01-01
Molecular simulation is a very powerful toolbox in modern molecular modeling, and enables us to follow and understand structure and dynamics with extreme detail--literally on scales where motion of individual atoms can be tracked. This chapter focuses on the two most commonly used methods, namely, energy minimization and molecular dynamics, that, respectively, optimize structure and simulate the natural motion of biological macromolecules. The common theoretical framework based on statistical mechanics is covered briefly as well as limitations of the computational approach, for instance, the lack of quantum effects and limited timescales accessible. As a practical example, a full simulation of the protein lysozyme in water is described step by step, including examples of necessary hardware and software, how to obtain suitable starting molecular structures, immersing it in a solvent, choosing good simulation parameters, and energy minimization. The chapter also describes how to analyze the simulation in terms of potential energies, structural fluctuations, coordinate stability, geometrical features, and, finally, how to create beautiful ray-traced movies that can be used in presentations.
Computer Modeling and Simulation
Pronskikh, V. S.
2014-05-09
Verification and validation of computer codes and models used in simulation are two aspects of the scientific practice of high importance and have recently been discussed by philosophers of science. While verification is predominantly associated with the correctness of the way a model is represented by a computer code or algorithm, validation more often refers to model’s relation to the real world and its intended use. It has been argued that because complex simulations are generally not transparent to a practitioner, the Duhem problem can arise for verification and validation due to their entanglement; such an entanglement makes it impossible to distinguish whether a coding error or model’s general inadequacy to its target should be blamed in the case of the model failure. I argue that in order to disentangle verification and validation, a clear distinction between computer modeling (construction of mathematical computer models of elementary processes) and simulation (construction of models of composite objects and processes by means of numerical experimenting with them) needs to be made. Holding on to that distinction, I propose to relate verification (based on theoretical strategies such as inferences) to modeling and validation, which shares the common epistemology with experimentation, to simulation. To explain reasons of their intermittent entanglement I propose a weberian ideal-typical model of modeling and simulation as roles in practice. I suggest an approach to alleviate the Duhem problem for verification and validation generally applicable in practice and based on differences in epistemic strategies and scopes
NASA Astrophysics Data System (ADS)
Herrmann, H. J.; Müller, M.
For the last ten years there has been an enormous progress in the simulation of granular media like sand or powders. These simulations consist in simulating trajectories of each particle individually. Essentially one has to solve the Newton's equations including the effects of Coulomb friction and the physics occuring at a collision. But the details of the trajectories are not important for the collective behaviour. Therefore simplifications are introduced on the smallest scales. I will introduce various methods like molecular dynamics that are used to simulate large amounts of particles (over 109). Some of these medhods are based on the exploitation of parallelisation and metacomputing. Other approaches are more stochastic (DSMC Direct Simulation Monte Carlo) which simplify the calculation of collisions, positions and collision times. Very successful has been also the use of cellular automata which have been able to predict details such as the logarithmic tale of sand heaps. I will also discuss numerical techniques used for the surrounding fluid. This can be water in the case of sedimentation or air when one studies the formation of dunes in the desert. The calculation of velocity and pressure field of the fluid are done using multigrid techniques on parallel computers. We will compare the performance of the various techniques and show some benchmarks on the dependence on the size of the system, the density of particles and the number of processors used.
Variational calculation of transport coefficients in diffusive lattice gases
NASA Astrophysics Data System (ADS)
Arita, Chikashi; Krapivsky, P. L.; Mallick, Kirone
2017-03-01
A diffusive lattice gas is characterized by the diffusion coefficient depending only on the density. The Green-Kubo formula for diffusivity can be represented as a variational formula, but even when the equilibrium properties of a lattice gas are analytically known, the diffusion coefficient can be computed only in the exceptional situation when the lattice gas is gradient. In the general case, minimization over an infinite-dimensional space is required. We propose an approximation scheme based on minimizing over finite-dimensional subspaces of functions. The procedure is demonstrated for one-dimensional generalized exclusion processes in which each site can accommodate at most two particles. Our analytical predictions provide upper bounds for the diffusivity that are very close to simulation results throughout the entire density range. We also analyze nonequilibrium density profiles for finite chains coupled to reservoirs. The predictions for the profiles are in excellent agreement with simulations.
The Simulated Law Firm and Other Contemporary Law Simulations
ERIC Educational Resources Information Center
Hollander, Patricia A.
1978-01-01
Various modes of simulations currently used in law schools are reviewed, including the Simulated Law Firm (SLF) at SUNY Buffalo and various computer-aided teaching programs. Simulation and computer use in the legal profession is reported, followed by a historical description of simulations in teaching and research. Its effectiveness as a teaching…
Simulator verification techniques study. Integrated simulator self test system concepts
NASA Technical Reports Server (NTRS)
Montoya, G.; Wenglinski, T. H.
1974-01-01
Software and hardware requirements for implementing hardware self tests are presented in support of the development of training and procedures development simulators for the space shuttle program. Self test techniques for simulation hardware and the validation of simulation performance are stipulated. The requirements of an integrated simulator self system are analyzed. Readiness tests, fault isolation tests, and incipient fault detection tests are covered.
The Simulated Law Firm and Other Contemporary Law Simulations
ERIC Educational Resources Information Center
Hollander, Patricia A.
1978-01-01
Various modes of simulations currently used in law schools are reviewed, including the Simulated Law Firm (SLF) at SUNY Buffalo and various computer-aided teaching programs. Simulation and computer use in the legal profession is reported, followed by a historical description of simulations in teaching and research. Its effectiveness as a teaching…
Real time digital propulsion system simulation for manned flight simulators
NASA Technical Reports Server (NTRS)
Mihaloew, J. R.; Hart, C. E.
1978-01-01
A real time digital simulation of a STOL propulsion system was developed which generates significant dynamics and internal variables needed to evaluate system performance and aircraft interactions using manned flight simulators. The simulation ran at a real-to-execution time ratio of 8.8. The model was used in a piloted NASA flight simulator program to evaluate the simulation technique and the propulsion system digital control. The simulation is described and results shown. Limited results of the flight simulation program are also presented.
Simulation verification techniques study. Subsystem simulation validation techniques
NASA Technical Reports Server (NTRS)
Duncan, L. M.; Reddell, J. P.; Schoonmaker, P. B.
1974-01-01
Techniques for validation of software modules which simulate spacecraft onboard systems are discussed. An overview of the simulation software hierarchy for a shuttle mission simulator is provided. A set of guidelines for the identification of subsystem/module performance parameters and critical performance parameters are presented. Various sources of reference data to serve as standards of performance for simulation validation are identified. Environment, crew station, vehicle configuration, and vehicle dynamics simulation software are briefly discussed from the point of view of their interfaces with subsystem simulation modules. A detailed presentation of results in the area of vehicle subsystems simulation modules is included. A list of references, conclusions and recommendations are also given.
Agrawal, A.K.
1982-01-01
The title of this session is taken to imply the system-wide thermohydraulic simulation of liquid metal fast breeder reactors (LMFBR). One is interested in predicting the temperatures, pressures, and the coolant flow rates throughout the entire plant including the reactor core, the primary and secondary sodium heat transport circuits, the steam generating system as well as other auxiliary circuits. Such a simulation is needed for (1) scoping studies (i.e., in the pre-design phase of a plant), (2) detailed design development, (3) the safety analysis (post-design development phase), and (4) the operator training and plant operation. This session emphasizes the simulation of LMFBRs for only two key categories of transients: operational disturbances or events and the post-shutdown heat removal.
Constructive Engineering of Simulations
NASA Technical Reports Server (NTRS)
Snyder, Daniel R.; Barsness, Brendan
2011-01-01
Joint experimentation that investigates sensor optimization, re-tasking and management has far reaching implications for Department of Defense, Interagency and multinational partners. An adaption of traditional human in the loop (HITL) Modeling and Simulation (M&S) was one approach used to generate the findings necessary to derive and support these implications. Here an entity-based simulation was re-engineered to run on USJFCOM's High Performance Computer (HPC). The HPC was used to support the vast number of constructive runs necessary to produce statistically significant data in a timely manner. Then from the resulting sensitivity analysis, event designers blended the necessary visualization and decision making components into a synthetic environment for the HITL simulations trials. These trials focused on areas where human decision making had the greatest impact on the sensor investigations. Thus, this paper discusses how re-engineering existing M&S for constructive applications can positively influence the design of an associated HITL experiment.
Goodman, Dan F M; Brette, Romain
2009-09-01
"Brian" is a simulator for spiking neural networks (http://www.briansimulator.org). The focus is on making the writing of simulation code as quick and easy as possible for the user, and on flexibility: new and non-standard models are no more difficult to define than standard ones. This allows scientists to spend more time on the details of their models, and less on their implementation. Neuron models are defined by writing differential equations in standard mathematical notation, facilitating scientific communication. Brian is written in the Python programming language, and uses vector-based computation to allow for efficient simulations. It is particularly useful for neuroscientific modelling at the systems level, and for teaching computational neuroscience.
A generic multibody simulation
NASA Technical Reports Server (NTRS)
Hopping, K. A.; Kohn, W.
1986-01-01
Described is a dynamic simulation package which can be configured for orbital test scenarios involving multiple bodies. The rotational and translational state integration methods are selectable for each individual body and may be changed during a run if necessary. Characteristics of the bodies are determined by assigning components consisting of mass properties, forces, and moments, which are the outputs of user-defined environmental models. Generic model implementation is facilitated by a transformation processor which performs coordinate frame inversions. Transformations are defined in the initialization file as part of the simulation configuration. The simulation package includes an initialization processor, which consists of a command line preprocessor, a general purpose grammar, and a syntax scanner. These permit specifications of the bodies, their interrelationships, and their initial states in a format that is not dependent on a particular test scenario.
Robot graphic simulation testbed
NASA Technical Reports Server (NTRS)
Cook, George E.; Sztipanovits, Janos; Biegl, Csaba; Karsai, Gabor; Springfield, James F.
1991-01-01
The objective of this research was twofold. First, the basic capabilities of ROBOSIM (graphical simulation system) were improved and extended by taking advantage of advanced graphic workstation technology and artificial intelligence programming techniques. Second, the scope of the graphic simulation testbed was extended to include general problems of Space Station automation. Hardware support for 3-D graphics and high processing performance make high resolution solid modeling, collision detection, and simulation of structural dynamics computationally feasible. The Space Station is a complex system with many interacting subsystems. Design and testing of automation concepts demand modeling of the affected processes, their interactions, and that of the proposed control systems. The automation testbed was designed to facilitate studies in Space Station automation concepts.
NASA Technical Reports Server (NTRS)
Carlstrom, Nicholas Mercury
2016-01-01
This position with the Simulation and Graphics Branch (ER7) at Johnson Space Center (JSC) provided an introduction to vehicle hardware, mission planning, and simulation design. ER7 supports engineering analysis and flight crew training by providing high-fidelity, real-time graphical simulations in the Systems Engineering Simulator (SES) lab. The primary project assigned by NASA mentor and SES lab manager, Meghan Daley, was to develop a graphical simulation of the rendezvous, proximity operations, and docking (RPOD) phases of flight. The simulation is to include a generic crew/cargo transportation vehicle and a target object in low-Earth orbit (LEO). Various capsule, winged, and lifting body vehicles as well as historical RPOD methods were evaluated during the project analysis phase. JSC core mission to support the International Space Station (ISS), Commercial Crew Program (CCP), and Human Space Flight (HSF) influenced the project specifications. The simulation is characterized as a 30 meter +V Bar and/or -R Bar approach to the target object's docking station. The ISS was selected as the target object and the international Low Impact Docking System (iLIDS) was selected as the docking mechanism. The location of the target object's docking station corresponds with the RPOD methods identified. The simulation design focuses on Guidance, Navigation, and Control (GNC) system architecture models with station keeping and telemetry data processing capabilities. The optical and inertial sensors, reaction control system thrusters, and the docking mechanism selected were based on CCP vehicle manufacturer's current and proposed technologies. A significant amount of independent study and tutorial completion was required for this project. Multiple primary source materials were accessed using the NASA Technical Report Server (NTRS) and reference textbooks were borrowed from the JSC Main Library and International Space Station Library. The Trick Simulation Environment and User
Active optics simulation system
NASA Technical Reports Server (NTRS)
Chi, C. H.
1973-01-01
The active optics simulation system (AOSS) is a set of computer programs and associated software to be used in the development, design, and evaluation of a primary mirror control system for a large space telescope, (e.g., the tentatively proposed 3-meter telescope). The mathematical models of component subsystems and the solution of the physical processes that occur within the mirror surface control system were obtained, and based on these models AOSS simulates the behavior of the entire mirror surface control system as well as the behavior of the component subsystems. The program has a modular structure so that any subsystem module can be replaced or modified with minimum disruption of the rest of the simulation program.
Flight code validation simulator
Sims, B.A.
1995-08-01
An End-To-End Simulation capability for software development and validation of missile flight software on the actual embedded computer has been developed utilizing a 486 PC, i860 DSP coprocessor, embedded flight computer and custom dual port memory interface hardware. This system allows real-time interrupt driven embedded flight software development and checkout. The flight software runs in a Sandia Digital Airborne Computer (SANDAC) and reads and writes actual hardware sensor locations in which IMU (Inertial Measurements Unit) data resides. The simulator provides six degree of freedom real-time dynamic simulation, accurate real-time discrete sensor data and acts on commands and discretes from the flight computer. This system was utilized in the development and validation of the successful premier flight of the Digital Miniature Attitude Reference System (DMARS) in January 1995 at the White Sands Missile Range on a two stage attitude controlled sounding rocket.
[Simulation of mental illness].
Mastronardi, Vincenzo; Del Casale, Antonio
2012-01-01
The DSM-IV-TR defines the simulation an "intentional production of physical or psychological symptoms false or grossly exaggerated, motivated by external incentives". The first point to consider is that it has a near zero prevalence in the general population, occurring almost exclusively in people imprisoned, treated in Forensic Psychiatric Hospital, in individuals subjected to trial, or in personalities seen as deviated from a criminological point of view. Both the criteria to set diagnoses of simulation, previously examined by Foreal and Kaufman since 1943, and the relative suspicion indicators, not separated by 'reasons of simulated behavior, are taken into account. The work also addresses several other meanings of self injurious actions appointed by Bachler, as well as the associationist/mechanistic theories of the classical dynamic model and the differential diagnosis with other conditions of Psychiatric Interest and concludes with the topic of "Premeditation".
Collisionless galaxy simulations
NASA Technical Reports Server (NTRS)
Hohl, F.; Zang, T. A.; Miller, J. B.
1979-01-01
Three-dimensional fully self-consistent computer models were used to determine the evolution of galaxies consisting of 100 000 simulation stars. Comparison of two-dimensional simulations with three-dimensional simulations showed only a very slight stabilizing effect due to the additional degree of freedom. The addition of a fully self-consistent, nonrotating, exponential core/halo component resulted in considerable stabilization. A second series of computer experiments was performed to determine the collapse and relaxation of initially spherical, uniform density and uniform velocity dispersion stellar systems. The evolution of the system was followed for various amounts of angular momentum in solid body rotation. For initally low values of the angular momentum satisfying the Ostriker-Peebles stability criterion, the systems quickly relax to an axisymmetric shape and resemble elliptical galaxies in appearance. For larger values of the initial angular momentum bars develop and the systems undergo a much more drastic evolution.
Dean, T.D. ); Haney, M.J. )
1992-08-01
In this paper 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.
Probabilistic Fatigue: Computational Simulation
NASA Technical Reports Server (NTRS)
Chamis, Christos C.
2002-01-01
Fatigue is a primary consideration in the design of aerospace structures for long term durability and reliability. There are several types of fatigue that must be considered in the design. These include low cycle, high cycle, combined for different cyclic loading conditions - for example, mechanical, thermal, erosion, etc. The traditional approach to evaluate fatigue has been to conduct many tests in the various service-environment conditions that the component will be subjected to in a specific design. This approach is reasonable and robust for that specific design. However, it is time consuming, costly and needs to be repeated for designs in different operating conditions in general. Recent research has demonstrated that fatigue of structural components/structures can be evaluated by computational simulation based on a novel paradigm. Main features in this novel paradigm are progressive telescoping scale mechanics, progressive scale substructuring and progressive structural fracture, encompassed with probabilistic simulation. These generic features of this approach are to probabilistically telescope scale local material point damage all the way up to the structural component and to probabilistically scale decompose structural loads and boundary conditions all the way down to material point. Additional features include a multifactor interaction model that probabilistically describes material properties evolution, any changes due to various cyclic load and other mutually interacting effects. The objective of the proposed paper is to describe this novel paradigm of computational simulation and present typical fatigue results for structural components. Additionally, advantages, versatility and inclusiveness of computational simulation versus testing are discussed. Guidelines for complementing simulated results with strategic testing are outlined. Typical results are shown for computational simulation of fatigue in metallic composite structures to demonstrate the
Simulations of vortex generators
NASA Technical Reports Server (NTRS)
Koumoutsakos, P.
1995-01-01
We are interested in the study, via direct numerical simulations, of active vortex generators. Vortex generators may be used to modify the inner part of the boundary layer or to control separation thus enhancing the performance and maneuverability of aerodynamic configurations. We consider generators that consist of a surface cavity elongated in the stream direction and partially covered with a moving lid that at rest lies flush with the boundary. Streamwise vorticity is generated and ejected due to the oscillatory motion of the lid. The present simulations complement relevant experimental investigations of active vortex generators at NASA Ames and Stanford University (Saddoughi, 1994, and Jacobson and Reynolds, 1993). Jacobson and Reynolds (1993) used a piezoelectric device in water, allowing for small amplitude high frequency oscillations. They placed the lid asymmetrically on the cavity and observed a strong outward velocity at the small gap of the cavity. Saddoughi used a larger mechanically driven device in air to investigate this flow and he observed a jet emerging from the wide gap of the configuration, contrary to the findings of Jacobson and Reynolds. Our task is to simulate the flows generated by these devices and to conduct a parametric study that would help us elucidate the physical mechanisms present in the flow. Conventional computational schemes encounter difficulties when simulating flows around complex configurations undergoing arbitrary motions. Here we present a formulation that achieves this task on a purely Lagrangian frame by extending the formulation presented by Koumoutsakos, Leonard and Pepin (1994). The viscous effects are taken into account by modifying the strength of the particles, whereas fast multipole schemes employing hundreds of thousands of particles allow for high resolution simulations. The results of the present simulations would help us assess some of the effects of three-dimensionality in experiments and investigate the role
NASA Astrophysics Data System (ADS)
Cook, K. H.; Delgado, F.; Miller, M.; Saha, A.; Allsman, R.; Pinto, P.; Gee, P. A.
2005-12-01
We have developed an operations simulator for LSST and used it to explore design and operations parameter space for this large etendue telescope and its ten year survey mission. The design is modular, with separate science programs coded in separate modules. There is a sophisticated telescope module with all motions parametrized for ease of testing different telescope capabilities, e.g. effect of acceleration capabilities of various motors on science output. Sky brightness is calculated as a function of moon phase and separation. A sophisticated exposure time calculator has been developed for LSST which is being incorporated into the simulator to allow specification of S/N requirements. All important parameters for the telescope, the site and the science programs are easily accessible in configuration files. Seeing and cloud data from the three candidate LSST sites are used for our simulations. The simulator has two broad categories of science proposals: sky coverage and transient events. Sky coverage proposals base their observing priorities on a required number of observations for each field in a particular filter with specified conditions (maximum seeing, sky brightness, etc) and one is used for a weak lensing investigation. Transient proposals are highly configurable. A transient proposal can require sequential, multiple exposures in various filters with a specified sequence of filters, and require a particular cadence for multiple revisits to complete an observation sequence. Each science proposal ranks potential observations based upon the internal logic of that proposal. We present the results of a variety of mixed science program observing simulations, showing how varied programs can be carried out simultaneously, with many observations serving multiple science goals. The simulator has shown that LSST can carry out its multiple missions under a variety of conditions. KHC's work was performed under the auspices of the US DOE, NNSA by the Univ. of California
CAPS Simulation Environment Development
NASA Technical Reports Server (NTRS)
Murphy, Douglas G.; Hoffman, James A.
2005-01-01
The final design for an effective Comet/Asteroid Protection System (CAPS) will likely come after a number of competing designs have been simulated and evaluated. Because of the large number of design parameters involved in a system capable of detecting an object, accurately determining its orbit, and diverting the impact threat, a comprehensive simulation environment will be an extremely valuable tool for the CAPS designers. A successful simulation/design tool will aid the user in identifying the critical parameters in the system and eventually allow for automatic optimization of the design once the relationships of the key parameters are understood. A CAPS configuration will consist of space-based detectors whose purpose is to scan the celestial sphere in search of objects likely to make a close approach to Earth and to determine with the greatest possible accuracy the orbits of those objects. Other components of a CAPS configuration may include systems for modifying the orbits of approaching objects, either for the purpose of preventing a collision or for positioning the object into an orbit where it can be studied or used as a mineral resource. The Synergistic Engineering Environment (SEE) is a space-systems design, evaluation, and visualization software tool being leveraged to simulate these aspects of the CAPS study. The long-term goal of the SEE is to provide capabilities to allow the user to build and compare various CAPS designs by running end-to-end simulations that encompass the scanning phase, the orbit determination phase, and the orbit modification phase of a given scenario. Herein, a brief description of the expected simulation phases is provided, the current status and available features of the SEE software system is reported, and examples are shown of how the system is used to build and evaluate a CAPS detection design. Conclusions and the roadmap for future development of the SEE are also presented.
Emotional Intelligence and Simulation.
McKinley, Sophia K; Phitayakorn, Roy
2015-08-01
Emotional intelligence (EI) is an established concept in the business literature with evidence that it is an important factor in determining career achievement. There is increasing interest in the role that EI has in medical training, but it is still a nascent field. This article reviews the EI literature most relevant to surgical training and proposes that simulation offers many benefits to the development of EI. Although there are many unanswered questions, it is expected that future research will demonstrate the effectiveness of using simulation to develop EI within surgery. Copyright © 2015 Elsevier Inc. All rights reserved.
NASA Technical Reports Server (NTRS)
Fowell, Richard A.
1989-01-01
Most simulation plots are heavily oversampled. Ignoring unnecessary data points dramatically reduces plot time with imperceptible effect on quality. The technique is suited to most plot devices. The departments laser printer's speed was tripled for large simulation plots by data thinning. This reduced printer delays without the expense of a faster laser printer. Surpisingly, it saved computer time as well. All plot data are now thinned, including PostScript and terminal plots. The problem, solution, and conclusions are described. The thinning algorithm is described and performance studies are presented. To obtain FORTRAN 77 or C source listings, mail a SASE to the author.
Simulation modeling of carcinogenesis.
Ellwein, L B; Cohen, S M
1992-03-01
A discrete-time simulation model of carcinogenesis is described mathematically using recursive relationships between time-varying model variables. The dynamics of cellular behavior is represented within a biological framework that encompasses two irreversible and heritable genetic changes. Empirical data and biological supposition dealing with both control and experimental animal groups are used together to establish values for model input variables. The estimation of these variables is integral to the simulation process as described in step-by-step detail. Hepatocarcinogenesis in male F344 rats provides the basis for seven modeling scenarios which illustrate the complexity of relationships among cell proliferation, genotoxicity, and tumor risk.
Terascale Optimal PDE Simulations
David Keyes
2009-07-28
The Terascale Optimal PDE Solvers (TOPS) Integrated Software Infrastructure Center (ISIC) was created to develop and implement algorithms and support scientific investigations performed by DOE-sponsored researchers. These simulations often involve the solution of partial differential equations (PDEs) on terascale computers. The TOPS Center researched, developed and deployed an integrated toolkit of open-source, optimal complexity solvers for the nonlinear partial differential equations that arise in many DOE application areas, including fusion, accelerator design, global climate change and reactive chemistry. The algorithms created as part of this project were also designed to reduce current computational bottlenecks by orders of magnitude on terascale computers, enabling scientific simulation on a scale heretofore impossible.
Visual simulation of radiographs
Laguna, G.
1985-01-18
A method for computer simulation of radiographs has been added to the LLNL version of the solid modeler TIPS-1 (Technical Information Processing System-1). This new tool will enable an engineer to compare an actual radiograph of a solid to its computer-generated counterpart. The appearance of discrepancies between the two can be an indication of flaws in the solid object. Simulated radiographs can also be used to preview the placement of x-ray sources to focus on areas of concern before actual radiographs are made.
Wellbore simulation - case studies
Freeston, Derek; Gunn, Calum
1993-01-28
The use of a wellbore simulator, WELLSIM, to characterise the effects of multi-feed inflow on wellbore pressure-temperature characteristics, and diameter changes to a well on the deliverability curve, is discussed. Matching analyses are performed with the simulator on a well which has a number of two-phase and liquid infeeds, and it is demonstrated that good matches to both pressure and temperature profiles can be achieved. The significance of the reservoir/feed response curve for a steam well is illustrated, and the optimisation of wellbore diameter is shown to be related to whether the discharge is wellbore or reservoir controlled.
Simulations of laser undulators
NASA Astrophysics Data System (ADS)
Milton, S. V.; Biedron, S. B.; Einstein, J. E.
2016-09-01
We perform a series of single-pass, one-D free-electron laser simulations based on an electron beam from a standard linear accelerator coupled with a so-called laser undulator, a specialized device that is more compact than a standard undulator based on magnetic materials. The longitudinal field profiles of such lasers undulators are intriguing as one must and can tailor the profile for the needs of creating the virtual undulator. We present and discuss several results of recent simulations and our future steps.
Kenny, Gerard
2016-01-01
This topic for debate explores how simulation based education has become an area where Higher Education providers look to deliver on an agenda of recruiting, educating and assessing for compassion. This paper offers that rather than SBE being a forum for developing and promoting compassion it may actually be achieving the opposite both for those we educate and those they in turn care for. It does this through introducing two ideas, near enemies and Jung's shadow and uses these ideas to explore our understanding and expression of compassion through simulation.
NASA Technical Reports Server (NTRS)
Joncas, K. P.
1972-01-01
Concepts and techniques for identifying and simulating both the steady state and dynamic characteristics of electrical loads for use during integrated system test and evaluation are discussed. The investigations showed that it is feasible to design and develop interrogation and simulation equipment to perform the desired functions. During the evaluation, actual spacecraft loads were interrogated by stimulating the loads with their normal input voltage and measuring the resultant voltage and current time histories. Elements of the circuits were optimized by an iterative process of selecting element values and comparing the time-domain response of the model with those obtained from the real equipment during interrogation.
Financing a Simulation Center.
Tsuda, Shawn; Mohsin, Adnan; Jones, Daniel
2015-08-01
As simulation-based training has become established within medical and health professional disciplines, skills training laboratories have become a standard in surgery training programs. In 2008, the American College of Surgeons and Association of Program Directors in Surgery developed a simulation-based surgical skills curriculum; the Residency Review Committee for Surgery of the Accreditation Council for Graduate Medical Education mandated access to skills laboratories for all surgery programs. Establishing a surgical skills laboratory and adapting the training curriculum requires a significant amount of resources. This article discusses the financial aspects of establishing a training center, from funding opportunities to budgeting considerations. Copyright © 2015 Elsevier Inc. All rights reserved.
NASA Astrophysics Data System (ADS)
Pepin, Eric W.; Olenick, R. P.
2006-12-01
The University of Dallas Department of Physics requires a sophomore-year computational course for all physics majors. The course introduces students to modeling classical and quantum systems with appropriate numerical methods. Students, as part of a course project, have developed charming visual simulations that have then been refined and used to educate subsequent undergraduates. In this poster session we will present several VPython simulations ranging from baseball pitches as viewed from around the field to quantum scattering and from galaxy formation to dielectric breakdown. We will discuss how they are used to make underlying concepts in physics more understandable.
NASA Technical Reports Server (NTRS)
1987-01-01
The proceedings of the conference are presented. The objective was to provide a forum for the discussion of the structure and status of existing computer programs which are used to simulate the dynamics of a variety of tether applications in space. A major topic was different simulation models and the process of validating them. Guidance on future work in these areas was obtained from a panel discussion; the panel was composed of resource and technical managers and dynamic analysts in the tether field. The conclusions of this panel are also presented.
NASA Astrophysics Data System (ADS)
Lin, Yu-Pin; Chang, Tsun-Kuo; Teng, Tung-Po
2001-11-01
This study attempted to characterize the spatial patterns of lead (Pb) for further soil monitoring and remediation by comparing the sequential Gaussian simulation, simulated annealing techniques and ordinary kriging methods to delineate soil lead in a rice paddy field in the north of Changhua County, Taiwan. For reproducing the statistics of Pb and natural log Pb (ln(Pb)), simulation techniques yielded better results than ordinary kriging. Meanwhile, sequential Gaussian simulation and simulated annealing reproduced the spatial variation of the measured Pb and ln(Pb), as well as identified the global spatial continuity and discontinuity patterns. Furthermore, the simulated annealing method equaled the global measurement statistics and spatial patterns of Pb and ln(Pb) more so than sequential Gaussian simulation and kriging. Finally, the realizations generated by sequential Gaussian simulation displayed significantly higher local heterogeneity than those generated by simulated annealing. The realizations of simulated annealing simulation are consistent in presenting the spatial patterns of soil Pb.
Simulating neural systems with Xyce.
Schiek, Richard Louis; Thornquist, Heidi K.; Mei, Ting; Warrender, Christina E.; Aimone, James Bradley; Teeter, Corinne; Duda, Alex M.
2012-12-01
Sandias parallel circuit simulator, Xyce, can address large scale neuron simulations in a new way extending the range within which one can perform high-fidelity, multi-compartment neuron simulations. This report documents the implementation of neuron devices in Xyce, their use in simulation and analysis of neuron systems.
History Microcomputer Simulations: An Update.
ERIC Educational Resources Information Center
Sargent, James E.
1985-01-01
This article summarizes seven currently available microcomputer simulations for history. The seven included are: Government Simulations (Prentice-Hall, 1984), Nomination (Brady Company, 1984), Tigers in the Snow (Strategic Simulations, 1981), Lincoln's Decisions (Educational Activities, 1982), Watergate Simulation (Social Science Research and…
History Microcomputer Simulations: An Update.
ERIC Educational Resources Information Center
Sargent, James E.
1985-01-01
This article summarizes seven currently available microcomputer simulations for history. The seven included are: Government Simulations (Prentice-Hall, 1984), Nomination (Brady Company, 1984), Tigers in the Snow (Strategic Simulations, 1981), Lincoln's Decisions (Educational Activities, 1982), Watergate Simulation (Social Science Research and…
Simulation in International Relations Education.
ERIC Educational Resources Information Center
Starkey, Brigid A.; Blake, Elizabeth L.
2001-01-01
Discusses the educational implications of simulations in international relations. Highlights include the development of international relations simulations; the role of technology; the International Communication and Negotiation Simulations (ICONS) project at the University of Maryland; evolving information technology; and simulating real-world…
A Mathematical Model of Network Communication
2010-05-03
Flow Network Simulation Proceedings of the Seventeenth Workshop on Parallel and Distributed Simulation, 2003 [14] Daniel Figueiredo, Benyuan Liu, Yang...1973 [25] Daniel H. Rothman and Stéphane Zaleski Lattice Gas Cellular Automata; Simple Models of Complex hydrodynamics. Cambridge Univesity text, 1997
Trajectory constraints in qualitative simulation
Brajnik, G.; Clancy, D.J.
1996-12-31
We present a method for specifying temporal constraints on trajectories of dynamical systems and enforcing them during qualitative simulation. This capability can be used to focus a simulation, simulate non-autonomous and piecewise-continuous systems, reason about boundary condition problems and incorporate observations into the simulation. The method has been implemented in TeQSIM, a qualitative simulator that combines the expressive power of qualitative differential equations with temporal logic. It interleaves temporal logic model checking with the simulation to constrain and refine the resulting predicted behaviors and to inject discontinuous changes into the simulation.
The history of medical simulation.
Rosen, Kathleen R
2008-06-01
The historical roots of simulation might be described with the broadest definition of medical simulation: "an imitation of some real thing, state of affairs, or process" for the practice of skills, problem solving, and judgment. From the first "blue box" flight simulator to the military's impetus in the transfer of modeling and simulation technology to medicine, worldwide acceptance of simulation training is growing. Large collaborative simulation centers support the expectation of increases in multidisciplinary, interprofessional, and multimodal simulation training. Virtual worlds, both immersive and Web-based, are at the frontier of innovation in medical education.
Multipebble Simulations for Alternating Automata
NASA Astrophysics Data System (ADS)
Clemente, Lorenzo; Mayr, Richard
We study generalized simulation relations for alternating Büchi automata (ABA), as well as alternating finite automata. Having multiple pebbles allows the Duplicator to "hedge her bets" and delay decisions in the simulation game, thus yielding a coarser simulation relation. We define (k 1,k 2)-simulations, with k 1/k 2 pebbles on the left/right, respectively. This generalizes previous work on ordinary simulation (i.e., (1,1)-simulation) for nondeterministic Büchi automata (NBA)[4] in and ABA in [5], and (1,k)-simulation for NBA in [3].
ICAAS piloted simulation results
NASA Astrophysics Data System (ADS)
Landy, R. J.; Halski, P. J.; Meyer, R. P.
1994-05-01
This paper reports piloted simulation results from the Integrated Control and Avionics for Air Superiority (ICAAS) piloted simulation evaluations. The program was to develop, integrate, and demonstrate critical technologies which will enable United States Air Force tactical fighter 'blue' aircraft to achieve superiority and survive when outnumbered by as much as four to one by enemy aircraft during air combat engagements. Primary emphasis was placed on beyond visual range (BVR) combat with provisions for effective transition to close-in combat. The ICAAS system was developed and tested in two stages. The first stage, called low risk ICAAS, was defined as employing aircraft and avionics technology with an initial operational date no later than 1995. The second stage, called medium risk ICAAS, was defined as employing aircraft and avionics technology with an initial operational date no later than 1998. Descriptions of the low risk and medium risk simulation configurations are given. Normalized (unclassified) results from both the low risk and medium risk ICAAS simulations are discussed. The results show the ICAAS system provided a significant improvement in air combat performance when compared to a current weapon system. Data are presented for both current generation and advanced fighter aircraft. The ICAAS technologies which are ready for flight testing in order to transition to the fighter fleet are described along with technologies needing additional development.
Introduction. Biomolecular simulation
Mulholland, Adrian J.
2008-01-01
‘Everything that living things do can be understood in terms of the jigglings and wigglings of atoms’ as Richard Feynman provocatively stated nearly 50 years ago. But how can we ‘see’ this wiggling and jiggling and understand how it drives biology? Increasingly, computer simulations of biological macromolecules are helping to meet this challenge. PMID:18826912
Introduction. Biomolecular simulation.
Mulholland, Adrian J
2008-12-06
'Everything that living things do can be understood in terms of the jigglings and wigglings of atoms' as Richard Feynman provocatively stated nearly 50 years ago. But how can we 'see' this wiggling and jiggling and understand how it drives biology? Increasingly, computer simulations of biological macromolecules are helping to meet this challenge.
NASA Astrophysics Data System (ADS)
Smith, Nathan; Draznik, Peter; Frank, Nathan
2012-10-01
We have simulated an existing experimental design to determine the resolution improvement upon energy measurements of neutron unbound nuclei. A number of experiments of this type have been performed at the National Superconducting Cyclotron Laboratory (NSCL), located at Michigan State University. An excited nucleus is typically produced with a radioactive beam interacting with a passive Beryllium target. Many different nuclei are produced in experiment, each of which immediately decays into a charged particle and neutron. The charged particles are detected and the neutrons interact in scintillation detectors such as the Modular Neutron Array (MoNA) and Large Multi-Institutional Scintillation Array (LISA). In our simulation, we have constructed an active target that provides additional information such that the point of nuclear interaction within the target may be determined. This information improves the resolution in decay energy measurements of neutron unbound isotopes. This presentation will cover some aspects of the simulation process, as well as showing some of the results that demonstrate the simulated improvement over a passive target.
T.L. Rogerson
1980-01-01
A simple simulation model to predict rainfall for individual storms in central Arkansas is described. Output includes frequency distribution tables for days between storms and for storm size classes; a storm summary by day number (January 1 = 1 and December 31 = 365) and rainfall amount; and an annual storm summary that includes monthly values for rainfall and number...
NASA Astrophysics Data System (ADS)
Černý, Pavol; Henzinger, Thomas A.; Radhakrishna, Arjun
While a boolean notion of correctness is given by a preorder on systems and properties, a quantitative notion of correctness is defined by a distance function on systems and properties, where the distance between a system and a property provides a measure of "fit" or "desirability." In this article, we explore several ways how the simulation preorder can be generalized to a distance function. This is done by equipping the classical simulation game between a system and a property with quantitative objectives. In particular, for systems that satisfy a property, a quantitative simulation game can measure the "robustness" of the satisfaction, that is, how much the system can deviate from its nominal behavior while still satisfying the property. For systems that violate a property, a quantitative simulation game can measure the "seriousness" of the violation, that is, how much the property has to be modified so that it is satisfied by the system. These distances can be computed in polynomial time, since the computation reduces to the value problem in limit average games with constant weights. Finally, we demonstrate how the robustness distance can be used to measure how many transmission errors are tolerated by error correcting codes.
Evaluation Training: Simulation Exercises.
ERIC Educational Resources Information Center
Smith, Carl B.; Farr, Roger
The preparation of this simulation material package is guided by the concept of an evaluator as a decision-maker, based on the definition of evaluation as a continuous assessment concerned with answering decision-making questions. The continuous concept of evaluation is based on the model created by Egon Guba and Daniel Stufflebeam, named by its…
ERIC Educational Resources Information Center
Van Camp, Julie
1986-01-01
This article provides background on the voir dire (jury selection) process, explaining its importance to the outcome of a trial. Offers a simulation experience which has students take the role of lawyers interviewing 29 prospective jurors for an alcohol-related traffic accident involving a 20-year-old driver. Profiles for prospective jurors and…
NASA Technical Reports Server (NTRS)
Lee, Meemong; Weidner, Richard J.
2008-01-01
The Juno spacecraft is planned to launch in August of 2012 and would arrive at Jupiter four years later. The spacecraft would spend more than one year orbiting the planet and investigating the existence of an ice-rock core; determining the amount of global water and ammonia present in the atmosphere, studying convection and deep- wind profiles in the atmosphere; investigating the origin of the Jovian magnetic field, and exploring the polar magnetosphere. Juno mission management is responsible for mission and navigation design, mission operation planning, and ground-data-system development. In order to ensure successful mission management from initial checkout to final de-orbit, it is critical to share a common vision of the entire mission operation phases with the rest of the project teams. Two major challenges are 1) how to develop a shared vision that can be appreciated by all of the project teams of diverse disciplines and expertise, and 2) how to continuously evolve a shared vision as the project lifecycle progresses from formulation phase to operation phase. The Juno mission simulation team addresses these challenges by developing agile and progressive mission models, operation simulations, and real-time visualization products. This paper presents mission simulation visualization network (MSVN) technology that has enabled a comprehensive mission simulation suite (MSVN-Juno) for the Juno project.
Smoothed Particle Hydrodynamic Simulator
2016-10-05
This code is a highly modular framework for developing smoothed particle hydrodynamic (SPH) simulations running on parallel platforms. The compartmentalization of the code allows for rapid development of new SPH applications and modifications of existing algorithms. The compartmentalization also allows changes in one part of the code used by many applications to instantly be made available to all applications.
Hamlet, Benjamin Roger
2009-02-01
Ion traps present a potential architecture for future quantum computers. These computers are of interest due to their increased power over classical computers stemming from the superposition of states and the resulting capability to simultaneously perform many computations. This paper describes a software application used to prepare and visualize simulations of trapping and maneuvering ions in ion traps.
NASA Astrophysics Data System (ADS)
Berendsen, Herman J. C.
2004-06-01
The simulation of physical systems requires a simplified, hierarchical approach which models each level from the atomistic to the macroscopic scale. From quantum mechanics to fluid dynamics, this book systematically treats the broad scope of computer modeling and simulations, describing the fundamental theory behind each level of approximation. Berendsen evaluates each stage in relation to its applications giving the reader insight into the possibilities and limitations of the models. Practical guidance for applications and sample programs in Python are provided. With a strong emphasis on molecular models in chemistry and biochemistry, this book will be suitable for advanced undergraduate and graduate courses on molecular modeling and simulation within physics, biophysics, physical chemistry and materials science. It will also be a useful reference to all those working in the field. Additional resources for this title including solutions for instructors and programs are available online at www.cambridge.org/9780521835275. The first book to cover the wide range of modeling and simulations, from atomistic to the macroscopic scale, in a systematic fashion Providing a wealth of background material, it does not assume advanced knowledge and is eminently suitable for course use Contains practical examples and sample programs in Python
Service Learning and Simulations
ERIC Educational Resources Information Center
Jenkins, Shannon
2010-01-01
Both service learning and simulations have been shown to positively impact student outcomes, but they are not often used together. This article examines how to effectively combine these active learning styles to reap the benefits of both. After examining a case in which the two were combined and the impact this approach had on student evaluations…
Graphical Interfaces for Simulation.
ERIC Educational Resources Information Center
Hollan, J. D.; And Others
This document presents a discussion of the development of a set of software tools to assist in the construction of interfaces to simulations and real-time systems. Presuppositions to the approach to interface design that was used are surveyed, the tools are described, and the conclusions drawn from these experiences in graphical interface design…
Simulations of laser thrombolysis
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.
Army Aviation Simulation Survey
1992-07-01
being simulated. Whereas, the interface in a VE system is designed to be specific to the human user’s needs for sensory inputs and control outputs with... evaluacion of VE FY93 control panel operation Demonstration & evaluation of VE FY94/FY95 stick/throttle operation Demonstration & evaluation of VE FY96/FY97
NASA Technical Reports Server (NTRS)
Lee, Meemong; Weidner, Richard J.
2008-01-01
The Juno spacecraft is planned to launch in August of 2012 and would arrive at Jupiter four years later. The spacecraft would spend more than one year orbiting the planet and investigating the existence of an ice-rock core; determining the amount of global water and ammonia present in the atmosphere, studying convection and deep- wind profiles in the atmosphere; investigating the origin of the Jovian magnetic field, and exploring the polar magnetosphere. Juno mission management is responsible for mission and navigation design, mission operation planning, and ground-data-system development. In order to ensure successful mission management from initial checkout to final de-orbit, it is critical to share a common vision of the entire mission operation phases with the rest of the project teams. Two major challenges are 1) how to develop a shared vision that can be appreciated by all of the project teams of diverse disciplines and expertise, and 2) how to continuously evolve a shared vision as the project lifecycle progresses from formulation phase to operation phase. The Juno mission simulation team addresses these challenges by developing agile and progressive mission models, operation simulations, and real-time visualization products. This paper presents mission simulation visualization network (MSVN) technology that has enabled a comprehensive mission simulation suite (MSVN-Juno) for the Juno project.
Bolometer Simulation Using SPICE
NASA Technical Reports Server (NTRS)
Jones, Hollis H.; Aslam, Shahid; Lakew, Brook
2004-01-01
A general model is presented that assimilates the thermal and electrical properties of the bolometer - this block model demonstrates the Electro-Thermal Feedback (ETF) effect on the bolometers performance. This methodology is used to construct a SPICE model that by way of analogy combines the thermal and electrical phenomena into one simulation session. The resulting circuit diagram is presented and discussed.
Computer Simulation of Reading.
ERIC Educational Resources Information Center
Leton, Donald A.
In recent years, coding and decoding have been claimed to be the processes for converting one language form to another. But there has been little effort to locate these processes in the human learner or to identify the nature of the internal codes. Computer simulation of reading is useful because the similarities in the human reception and…
Imitation, Simulation, and Schizophrenia
Park, Sohee; Matthews, Natasha; Gibson, Crystal
2008-01-01
The social significance of imitation is that it provides internal tools for understanding the actions of others by simulating or forming internal representations of these actions. Imitation plays a central role in human social behavior by mediating diverse forms of social learning. However, imitation and simulation ability in schizophrenia has not been adequately addressed. The major aim of the present study was to investigate imitation ability in schizophrenia patients and healthy individuals by examining simple motor imitation that involved the replication of meaningless manual and oral gestures, and the imitation of emotional facial expressions, which has implications for mentalizing. A secondary aim of the present study was to investigate the relationships among imitation ability, social functioning, and working memory. Subjects were asked to mimic hand gestures, mouth movements, and facial expressions of others, online. Clinical symptoms, social competence, and working memory were also assessed. Patients with schizophrenia were significantly impaired on all imitation tasks. Imitation errors were significantly correlated with reduced social competence and increased negative symptoms. However, imitation ability was only weakly associated with working memory. To summarize, the present study examined the ability of patients with schizophrenia to imitate the behaviors demonstrated by others. The results indicate a fundamental impairment in imitation ability in schizophrenia and implicate a possible difficulty in simulation. Further research to determine the neural and developmental origins of this difficulty could be extremely helpful in elucidating the role of simulation in schizophrenia and to establish the complex relationships among mental representation, imitation, and social cognition. PMID:18499703
SPASIM: A Spacecraft Simulator
NASA Technical Reports Server (NTRS)
Liceaga, Carlos A.
1997-01-01
The SPAcecraft SIMulator (SPASIM) simulates the functions and resources of a spacecraft to quickly perform conceptual design (Phase A) trade-off and sensitivity analyses and uncover any operational bottlenecks during any part of the mission. Failure modes and operational contingencies can be evaluated allowing operational planning (what-if scenarios) and optimization for a range of mission scenarios. The payloads and subsystems are simulated, using a hierarchy of graphical models, in terms of how their functions affect resources such as propellant, power, and data. Any of the inputs and outputs of the payloads and subsystems can be plotted during the simulation or stored in a file so they can be used by other programs. Most trade-off analyses, including those that compare current versus advanced technology, can be performed by changing values in the parameter menus. However, when a component is replaced by one with a different functional architecture, its graphical model can also be modified or replaced by drawing from a component library. SPASIM has been validated using several spacecraft designs that were at least at the Critical Design Review level. The user and programmer guide, including figures, is available on line as a hypertext document. This is an easy-to-use and expandable tool which is based on MATLAB(R) and SIMULINK(R). It runs on Silicon Graphics Inc. workstations and personal computers with Windows 95(TM) or NT(TM).
2013-12-04
ISS038-E-011708 (4 Dec. 2013) --- In the International Space Station?s Zvezda Service Module, Russian cosmonaut Sergey Ryazanskiy, Expedition 38 flight engineer, reads a procedures checklist during an emergency simulation drill with participation from flight controllers on the ground. During the exercise, the crew practiced emergency communication and procedures in response to a predetermined scenario such as pressure leak.
Simulated proteinuria and haematuria.
Englis, M; Martinek, V; Jirka, J; Schück, O; Velická, V
1983-01-01
In nephrology, like in other branches of medicine, falsification is motivated by a desire for profit or is an expression of some mental disorder. Three cases are described in which artificial proteinuria and haematuria were diagnosed by agarose gel electrophoresis of urinary proteins and a simulation and aggravation of renal disease was disclosed.
Computer Simulation of Mutagenesis.
ERIC Educational Resources Information Center
North, J. C.; Dent, M. T.
1978-01-01
A FORTRAN program is described which simulates point-substitution mutations in the DNA strands of typical organisms. Its objective is to help students to understand the significance and structure of the genetic code, and the mechanisms and effect of mutagenesis. (Author/BB)
Simulations of immersion lithography
NASA Astrophysics Data System (ADS)
Bai, Min; Lei, Junjiang; Zhang, Lin; Shiely, James P.
2005-05-01
Immersion lithography has been regarded as the most viable contender to extend the resolution capability of optical lithography using 193nm wavelength. In parallel with the tremendous effort of overcoming the engineering challenges in immersion, support from modeling and simulations is strongly needed. Although immersion simulation has become available through a number of simulation tools, we need to investigate the model generation and its compatibility within the context of full-chip optical proximity correction (OPC). In this paper, we will describe the physics of a full vector model that is necessary for the high NA optical modeling under immersion. In this full vector model, we consider not only the plane wave decomposition as light travels from the mask to wafer plane, but also the refraction, transmission and reflection of light through a thin film stack on the wafer. We integrated this comprehensive vector model into Synopsys OPC modeling tool ProGen. Through ProGen simulation results, we will discuss several important merits of immersion lithography, as well as the full portability of immersion models into OPC process flow.
NASA Astrophysics Data System (ADS)
Giblin, Tom; Mertens, James; Starkman, Glenn
2017-05-01
Powerful computers are now allowing cosmologists to solve Einstein’s frighteningly complex equations of general relativity in a cosmological setting for the first time. Tom Giblin, James Mertens and Glenn Starkman describe how this new era of simulations could transform our understanding of the universe
1981-12-31
Bill Nevins, LLNL Use of the ZED postprocessor. Oct 9 Tom Crystal Kinetic simulations of Tokamak TEM Oct 23 Niels Otani The AIC instability...Ion test oarticles advanced in the equilibrium fields do maintain their initial distri- bution function, as desired. The next step is to be wholly
Simulating the Eucaryotic Chromosome.
ERIC Educational Resources Information Center
Spencer, Leo E.
1985-01-01
The use of simple materials to illustrate complex biological concepts provides benefits to all students, particularly the visually handicapped. A list of materials needed and discussion of procedures used are given for (1) a nucleosome simulation and (2) a supercoiled model of condensed DNA. (DH)
Teleoperator docking simulation
NASA Technical Reports Server (NTRS)
Kirkpatrick, M.; Brye, R. G.
1974-01-01
A simulation study is described of the translation, station keeping and final approach segments of the teleoperator implemented at MSFC. An effort is made to identify the teleoperator visual system design parameters which influence operator performance and to determine human factors design requirements for free flying teleoperators.
Helicopter simulator qualification
NASA Technical Reports Server (NTRS)
Hampson, Brian
1992-01-01
CAE has extensive experience in building helicopter simulators and has participated in group working sessions for fixed-wing advisory circulars. Against this background, issues that should be addressed in establishing helicopter approval criteria were highlighted. Some of these issues are not immediately obvious and may, indeed, be more important than the criteria a themselves.
Statistics by Computer Simulation.
ERIC Educational Resources Information Center
Lotz, A.
1995-01-01
Describes an experiment from a physical chemistry course that consists of a computer simulation of throwing dice and the statistics involved. The experiment is designed to improve students' understanding of statistical evaluation of experimental data and to introduce programming techniques. (DDR)
ERIC Educational Resources Information Center
Kostadinov, Boyan
2013-01-01
This article attempts to introduce the reader to computational thinking and solving problems involving randomness. The main technique being employed is the Monte Carlo method, using the freely available software "R for Statistical Computing." The author illustrates the computer simulation approach by focusing on several problems of…
2009-01-13
control system (AFCS) ON and OFF. Flight control axes which include a trim system will be tested with both TRIM ON and OFF and stability augmentation system (SAS...Flight Test Manual HQ Handling Qualities M&S Modeling and Simulation SAS Stability Augmentation System SCAS Stability and Control
Parallel Dislocation Simulator
2006-10-30
ParaDiS is software capable of simulating the motion, evolution, and interaction of dislocation networks in single crystals using massively parallel computer architectures. The software is capable of outputting the stress-strain response of a single crystal whose plastic deformation is controlled by the dislocation processes.
Data Systems Dynamic Simulator
NASA Technical Reports Server (NTRS)
Rouff, Christopher; Clark, Melana; Davenport, Bill; Message, Philip
1993-01-01
The Data System Dynamic Simulator (DSDS) is a discrete event simulation tool. It was developed for NASA for the specific purpose of evaluating candidate architectures for data systems of the Space Station era. DSDS provides three methods for meeting this requirement. First, the user has access to a library of standard pre-programmed elements. These elements represent tailorable components of NASA data systems and can be connected in any logical manner. Secondly, DSDS supports the development of additional elements. This allows the more sophisticated DSDS user the option of extending the standard element set. Thirdly, DSDS supports the use of data streams simulation. Data streams is the name given to a technique that ignores packet boundaries, but is sensitive to rate changes. Because rate changes are rare compared to packet arrivals in a typical NASA data system, data stream simulations require a fraction of the CPU run time. Additionally, the data stream technique is considerably more accurate than another commonly-used optimization technique.
Human Simulated Diving Experiments.
ERIC Educational Resources Information Center
Bruce, David S.; Speck, Dexter F.
1979-01-01
This report details several simulated divinq experiments on the human. These are suitable for undergraduate or graduate laboratories in human or environmental physiology. The experiment demonstrates that a diving reflex is precipitated by both facial cooling and apnea. (Author/RE)
Service Learning and Simulations
ERIC Educational Resources Information Center
Jenkins, Shannon
2010-01-01
Both service learning and simulations have been shown to positively impact student outcomes, but they are not often used together. This article examines how to effectively combine these active learning styles to reap the benefits of both. After examining a case in which the two were combined and the impact this approach had on student evaluations…
ERIC Educational Resources Information Center
Kappan, David
Many educators in facilitative roles have approached the subject of visual disabilities by constructing activities designed to simulate blindness, using a blindfold or similar device. Participants are subsequently encouraged to perform rudimentary tasks such as eating a meal or moving about with a sighted companion as a guide. Frequently,…
ERIC Educational Resources Information Center
Guyton, J. W.
1972-01-01
An inexpensive, simple mechanical model of a fault can be produced to simulate the effects leading to an earthquake. This model has been used successfully with students from elementary to college levels and can be demonstrated to classes as large as thirty students. (DF)
Solar simulator mirror refurbishment
NASA Technical Reports Server (NTRS)
Leverton, W. R.
1974-01-01
Solar simulator mirrors were refurbished. Two different refurbishment methods were employed. In the first, the electroformed mirror replica was removed from the casting and replaced with a new mirror replica. In the second, only the aluminized surface, with its protective overcoat, was removed from the mirror and replaced after cleaning of the nickel surface.
General Data Simulation Program.
ERIC Educational Resources Information Center
Burns, Edward
Described is a computer program written in FORTRAN IV which offers considerable flexibility in generating simulated data pertinent to education and educational psychology. The user is allowed to specify the number of samples, data sets, and variables, together with the population means, standard deviations and intercorrelations. In addition the…
Computer Simulation of Mutagenesis.
ERIC Educational Resources Information Center
North, J. C.; Dent, M. T.
1978-01-01
A FORTRAN program is described which simulates point-substitution mutations in the DNA strands of typical organisms. Its objective is to help students to understand the significance and structure of the genetic code, and the mechanisms and effect of mutagenesis. (Author/BB)
Simulation of phase structures
Lawson, J.
1995-04-20
This memo outlines a procedure developed by the author to extract information from phase measurements and produce a simulated phase structure for use in modeling optical systems, including characteristic optics for the Beamlet and NIF laser systems. The report includes an IDL program listing.
ERIC Educational Resources Information Center
Kostadinov, Boyan
2013-01-01
This article attempts to introduce the reader to computational thinking and solving problems involving randomness. The main technique being employed is the Monte Carlo method, using the freely available software "R for Statistical Computing." The author illustrates the computer simulation approach by focusing on several problems of…
Computer simulation of earthquakes
NASA Technical Reports Server (NTRS)
Cohen, S. C.
1976-01-01
Two computer simulation models of earthquakes were studied for the dependence of the pattern of events on the model assumptions and input parameters. Both models represent the seismically active region by mechanical blocks which are connected to one another and to a driving plate. The blocks slide on a friction surface. In the first model elastic forces were employed and time independent friction to simulate main shock events. The size, length, and time and place of event occurrence were influenced strongly by the magnitude and degree of homogeniety in the elastic and friction parameters of the fault region. Periodically reoccurring similar events were frequently observed in simulations with near homogeneous parameters along the fault, whereas, seismic gaps were a common feature of simulations employing large variations in the fault parameters. The second model incorporated viscoelastic forces and time-dependent friction to account for aftershock sequences. The periods between aftershock events increased with time and the aftershock region was confined to that which moved in the main event.
Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
Naiman, Cynthia
2006-01-01
The NASA Glenn Research Center, in partnership with the aerospace industry, other government agencies, and academia, is leading the effort to develop an advanced multidisciplinary analysis environment for aerospace propulsion systems called the Numerical Propulsion System Simulation (NPSS). NPSS is a framework for performing analysis of complex systems. The initial development of NPSS focused on the analysis and design of airbreathing aircraft engines, but the resulting NPSS framework may be applied to any system, for example: aerospace, rockets, hypersonics, power and propulsion, fuel cells, ground based power, and even human system modeling. NPSS provides increased flexibility for the user, which reduces the total development time and cost. It is currently being extended to support the NASA Aeronautics Research Mission Directorate Fundamental Aeronautics Program and the Advanced Virtual Engine Test Cell (AVETeC). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structure, and heat transfer with numerical zooming on component codes. Zooming is the coupling of analyses at various levels of detail. NPSS development includes capabilities to facilitate collaborative engineering. The NPSS will provide improved tools to develop custom components and to use capability for zooming to higher fidelity codes, coupling to multidiscipline codes, transmitting secure data, and distributing simulations across different platforms. These powerful capabilities extend NPSS from a zero-dimensional simulation tool to a multi-fidelity, multidiscipline system-level simulation tool for the full development life cycle.
2014-09-15
Two simulations show the differences between a battery being drained at a slower rate, over a full hour, versus a faster rate, only six minutes (a tenth of an hour). In both cases battery particles go from being fully charged (green) to fully drained (red), but there are significant differences in the patterns of discharge based on the rate.
Enabling immersive simulation.
McCoy, Josh; Mateas, Michael; Hart, Derek H.; Whetzel, Jonathan; Basilico, Justin Derrick; Glickman, Matthew R.; Abbott, Robert G.
2009-02-01
The object of the 'Enabling Immersive Simulation for Complex Systems Analysis and Training' LDRD has been to research, design, and engineer a capability to develop simulations which (1) provide a rich, immersive interface for participation by real humans (exploiting existing high-performance game-engine technology wherever possible), and (2) can leverage Sandia's substantial investment in high-fidelity physical and cognitive models implemented in the Umbra simulation framework. We report here on these efforts. First, we describe the integration of Sandia's Umbra modular simulation framework with the open-source Delta3D game engine. Next, we report on Umbra's integration with Sandia's Cognitive Foundry, specifically to provide for learning behaviors for 'virtual teammates' directly from observed human behavior. Finally, we describe the integration of Delta3D with the ABL behavior engine, and report on research into establishing the theoretical framework that will be required to make use of tools like ABL to scale up to increasingly rich and realistic virtual characters.
ERIC Educational Resources Information Center
Guyton, J. W.
1972-01-01
An inexpensive, simple mechanical model of a fault can be produced to simulate the effects leading to an earthquake. This model has been used successfully with students from elementary to college levels and can be demonstrated to classes as large as thirty students. (DF)
NASA Astrophysics Data System (ADS)
Nørnberg, Per; Merrison, Jonathan P.; Gunnlaugsson, Haraldur P.
2010-05-01
Laboratory simulations of the Martian surface are of importance to broaden scientific understanding of the physical processes, but also in order to develop the technology necessary for exploration of the planet. The Mars Simulation Laboratory at Aarhus University [1] has been involved in such simulations for around ten years and has developed several experimental facilities for carrying out science or instrument testing under conditions similar to those at the Martian surface, specifically low pressure, low temperature and importantly recreating the wind flow environment and dust suspension (reproducing the Martian dusty aerosol) using Mars analogue material [2]. The science involved in this simulation work has covered a broad spectrum including, erosion induced mineralogy/chemistry, particulate electrification, magnetic properties of Martian dust, biological survival, UV induced chemistry/mineralogy (using a solar simulator), adhesion/cohesion processes and the wind driven transport of dust and sand [3,4]. With regard to technology the wind tunnel facilities have been used in the development of the latest wind and dust sensing instrumentation [5,6]. With support from the European Space Agency (ESA) and Danish national funding an advanced Mars simulation facility has recently been constructed (2009). This wind tunnel facility has a cross section of 2 x 1 m and a length of 8 m, a temperature range down to below -120C, wind speeds in excess of 20m/s, and automated dust control. With a range of (specialised) sensing instrumentation it provides the opportunity to perform a new generation of scientific experiments and allow testing and technology development in the most realistic and rigorous environment. As well as being available for the space agencies, this facility will be open to all potential scientific collaborators. Also European planetary scientists may benefit from support through the EU Europlanet FP7 networking programme. For more information on access
NASA Astrophysics Data System (ADS)
Delgado, Francisco; Saha, Abhijit; Chandrasekharan, Srinivasan; Cook, Kem; Petry, Catherine; Ridgway, Stephen
2014-08-01
The Operations Simulator for the Large Synoptic Survey Telescope (LSST; http://www.lsst.org) allows the planning of LSST observations that obey explicit science driven observing specifications, patterns, schema, and priorities, while optimizing against the constraints placed by design-specific opto-mechanical system performance of the telescope facility, site specific conditions as well as additional scheduled and unscheduled downtime. It has a detailed model to simulate the external conditions with real weather history data from the site, a fully parameterized kinematic model for the internal conditions of the telescope, camera and dome, and serves as a prototype for an automatic scheduler for the real time survey operations with LSST. The Simulator is a critical tool that has been key since very early in the project, to help validate the design parameters of the observatory against the science requirements and the goals from specific science programs. A simulation run records the characteristics of all observations (e.g., epoch, sky position, seeing, sky brightness) in a MySQL database, which can be queried for any desired purpose. Derivative information digests of the observing history are made with an analysis package called Simulation Survey Tools for Analysis and Reporting (SSTAR). Merit functions and metrics have been designed to examine how suitable a specific simulation run is for several different science applications. Software to efficiently compare the efficacy of different survey strategies for a wide variety of science applications using such a growing set of metrics is under development. A recent restructuring of the code allows us to a) use "look-ahead" strategies that avoid cadence sequences that cannot be completed due to observing constraints; and b) examine alternate optimization strategies, so that the most efficient scheduling algorithm(s) can be identified and used: even few-percent efficiency gains will create substantive scientific
NASA Astrophysics Data System (ADS)
Kohler, Susanna
2017-02-01
Formation of a coronal jet from twisted field lines that have reconnected with the ambient field. The colors show the radial velocity of the plasma. [Adapted from Szente et al. 2017]How do jets emitted from the Suns surface contribute to its corona and to the solar wind? In a recent study, a team of scientists performed complex three-dimensional simulations of coronal jets to answer these questions.Small ExplosionsCoronal jets are relatively small eruptions from the Suns surface, with heights of roughly 100 to 10,000 km, speeds of 10 to 1,000 km/s, and lifetimes of a few minutes to around ten hours. These jets are constantly present theyre emitted even from the quiet Sun, when activity is otherwise low and weve observed them with a fleet of Sun-watching space telescopes spanning the visible, extreme ultraviolet (EUV), and X-ray wavelength bands.A comparison of simulated observations based on the authors model (left panels) to actual EUV and X-ray observations of jets (right panels). [Szente et al. 2017]Due to their ubiquity, we speculate that these jets might contribute to heating the global solar corona (which is significantly hotter than the surface below it, a curiosity known as the coronal heating problem). We can also wonder what role these jets might play in driving the overall solar wind.Launching a JetLed by Judit Szente (University of Michigan), a team of scientists has explored the impact of coronal jets on the global corona and solar wind with a series of numerical simulations. Szente and collaborators used three-dimensional, magnetohydrodynamic simulations that provide realistic treatment of the solar atmosphere, the solar wind acceleration, and the complexities of heat transfer throughout the corona.In the authors simulations, a jet is initiated as a magnetic dipole rotates at the solar surface, winding up field lines. Magnetic reconnection between the twisted lines and the background field then launches the jet from the dense and hot solar
NASA Astrophysics Data System (ADS)
Baldi, Marco
2012-11-01
Cosmology is presently facing the deep mystery of the origin of the observed accelerated expansion of the Universe. Be it a cosmological constant, a homogeneous scalar field, or a more complex inhomogeneous field possibly inducing effective modifications of the laws of gravity, such elusive physical entity is indicated with the general term of “Dark Energy”. The growing role played by numerical N-body simulations in cosmological studies as a fundamental connection between theoretical modeling and direct observations has led to impressive advancements also in the development and application of specific algorithms designed to probe a wide range of Dark Energy scenarios. Over the last decade, a large number of independent and complementary investigations have been carried out in the field of Dark Energy N-body simulations, starting from the simplest case of homogeneous Dark Energy models up to the recent development of highly sophisticated iterative solvers for a variety of Modified Gravity theories. In this review -which is meant to be complementary to the general Review by Kuhlen et al. (2012) [1] published in this Volume - I will discuss the range of scenarios for the cosmic acceleration that have been successfully investigated by means of dedicated N-body simulations, and I will provide a broad summary of the main results that have been obtained in this rather new research field. I will focus the discussion on a few selected studies that have led to particularly significant advancements in the field, and I will provide a comprehensive list of references for a larger number of related works. Due to the vastness of the topic, the discussion will not enter into the finest details of the different implementations and will mainly focus on the outcomes of the various simulations studies. Although quite recent, the field of Dark Energy simulations has witnessed huge developments in the last few years, and presently stands as a reliable approach to the investigation
Multispectral Imaging Simulation
NASA Astrophysics Data System (ADS)
Loefer, Gene R.; Lao, Ken Q.
1987-09-01
Current aircraft have a requirement to operate at night and in adverse weather where optical imaging systems are inoperable. Imaging sensors operating at other wavelengths have the potential to provide vision through severe weather, but these systems need to be simulated before assuming the technological and financial risks involved in hardware development. Sensor and atmospheric models have been developed which simulate images at a variety of wavelengths. These models have been incorporated into a modified version of the IVEX Corporation Behold software which is used for the creation of three dimensional views of terrain data bases and includes fractal texturing and anti-aliasing. This new version, called Behold-ms, adds phenomenological models of material properties, such as surface roughness, emissivity, and temperature, and structured atmospheric weather models that consider path emission, backscatter, and specular/diffuse reflections of the sky. To date, images have been simulated in the visible (color), infrared (8-14pm), passive millimeter wave (35 GHz and 95 GHz), and active MMW (35 GHz and 95 GHz). These algorithms can be used for other windows over this spectral range. In order to accommodate the widely varying types of sensed energy while maintaining a practical amount of internal storage, a scheme for scaling each spectral band has been developed. Spatial resolution degradation due to diffraction, which is especially important at millimeter wavelengths, spatial sampling effects, and system noise models are also included. These sensor models and simulations have been used to examine adverse weather landing systems. Simulated images have also been used in image understanding research and spatial superresolution studies.
Reevaluating simulation in nursing education: beyond the human patient simulator.
Schiavenato, Martin
2009-07-01
The human patient simulator or high-fidelity mannequin has become synonymous with the word simulation in nursing education. Founded on a historical context and on an evaluation of the current application of simulation in nursing education, this article challenges that assumption as limited and restrictive. A definition of simulation and a broader conceptualization of its application in nursing education are presented. The need for an ideological basis for simulation in nursing education is highlighted. The call is made for theory to answer the question of why simulation is used in nursing to anchor its proper and effective application in nursing education.
Molecular Simulations in Astrobiology
NASA Technical Reports Server (NTRS)
Pohorille, Andrew; Wilson, Michael A.; Schweighofer, Karl; Chipot, Christophe; New, Michael H.
2000-01-01
One of the main goals of astrobiology is to understand the origin of cellular life. The most direct approach to this problem is to construct laboratory models of protocells. Such efforts, currently underway in the NASA Astrobiology Program, are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures that are capable of performing protocellular functions. Many of these functions, such as importing nutrients, capturing energy and responding to changes in the environment, are carried out by proteins bound to membranes. We use computer simulations to address the following questions about these proteins: (1) How do small proteins self-organize into ordered structures at water-membrane interfaces and insert into membranes? (2) How do peptides form membrane-spanning structures (e.g. channels)? (3) By what mechanisms do such structures perform their functions? The simulations are performed using the molecular dynamics method. In this method, Newton's equations of motion for each atom in the system are solved iteratively. At each time step, the forces exerted on each atom by the remaining atoms are evaluated by dividing them into two parts. Short-range forces are calculated in real space while long-range forces are evaluated in reciprocal space, using a particle-mesh algorithm which is of order O(NInN). With a time step of 2 femtoseconds, problems occurring on multi-nanosecond time scales (10(exp 6)-10(exp 8) time steps) are accessible. To address a broader range of problems, simulations need to be extended by three orders of magnitude, which requires algorithmic improvements and codes scalable to a large number of processors. Work in this direction is in progress. Two series of simulations are discussed. In one series, it is shown that nonpolar peptides, disordered in water, translocate to the nonpolar interior of the membrane and fold into helical structures (see Figure). Once in the membrane, the peptides
Molecular Simulations in Astrobiology
NASA Technical Reports Server (NTRS)
Pohorille, Andrew; Wilson, Michael A.; Schweighofer, Karl; Chipot, Christophe; New, Michael H.
2000-01-01
One of the main goals of astrobiology is to understand the origin of cellular life. The most direct approach to this problem is to construct laboratory models of protocells. Such efforts, currently underway in the NASA Astrobiology Program, are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures that are capable of performing protocellular functions. Many of these functions, such as importing nutrients, capturing energy and responding to changes in the environment, are carried out by proteins bound to membranes. We use computer simulations to address the following questions about these proteins: (1) How do small proteins self-organize into ordered structures at water-membrane interfaces and insert into membranes? (2) How do peptides form membrane-spanning structures (e.g. channels)? (3) By what mechanisms do such structures perform their functions? The simulations are performed using the molecular dynamics method. In this method, Newton's equations of motion for each atom in the system are solved iteratively. At each time step, the forces exerted on each atom by the remaining atoms are evaluated by dividing them into two parts. Short-range forces are calculated in real space while long-range forces are evaluated in reciprocal space, using a particle-mesh algorithm which is of order O(NInN). With a time step of 2 femtoseconds, problems occurring on multi-nanosecond time scales (10(exp 6)-10(exp 8) time steps) are accessible. To address a broader range of problems, simulations need to be extended by three orders of magnitude, which requires algorithmic improvements and codes scalable to a large number of processors. Work in this direction is in progress. Two series of simulations are discussed. In one series, it is shown that nonpolar peptides, disordered in water, translocate to the nonpolar interior of the membrane and fold into helical structures (see Figure). Once in the membrane, the peptides
NASA Lunar Regolith Simulant Program
NASA Technical Reports Server (NTRS)
Edmunson, J.; Betts, W.; Rickman, D.; McLemore, C.; Fikes, J.; Stoeser, D.; Wilson, S.; Schrader, C.
2010-01-01
Lunar regolith simulant production is absolutely critical to returning man to the Moon. Regolith simulant is used to test hardware exposed to the lunar surface environment, simulate health risks to astronauts, practice in situ resource utilization (ISRU) techniques, and evaluate dust mitigation strategies. Lunar regolith simulant design, production process, and management is a cooperative venture between members of the NASA Marshall Space Flight Center (MSFC) and the U.S. Geological Survey (USGS). The MSFC simulant team is a satellite of the Dust group based at Glenn Research Center. The goals of the cooperative group are to (1) reproduce characteristics of lunar regolith using simulants, (2) produce simulants as cheaply as possible, (3) produce simulants in the amount needed, and (4) produce simulants to meet users? schedules.