Science.gov

Sample records for general event-driven simulator

  1. Event-driven simulation in SELMON: An overview of EDSE

    NASA Technical Reports Server (NTRS)

    Rouquette, Nicolas F.; Chien, Steve A.; Charest, Leonard, Jr.

    1992-01-01

    EDSE (event-driven simulation engine), a model-based event-driven simulator implemented for SELMON, a tool for sensor selection and anomaly detection in real-time monitoring is described. The simulator is used in conjunction with a causal model to predict future behavior of the model from observed data. The behavior of the causal model is interpreted as equivalent to the behavior of the physical system being modeled. An overview of the functionality of the simulator and the model-based event-driven simulation paradigm on which it is based is provided. Included are high-level descriptions of the following key properties: event consumption and event creation, iterative simulation, synchronization and filtering of monitoring data from the physical system. Finally, how EDSE stands with respect to the relevant open issues of discrete-event and model-based simulation is discussed.

  2. Event-driven simulation of cerebellar granule cells.

    PubMed

    Carrillo, Richard R; Ros, Eduardo; Tolu, Silvia; Nieus, Thierry; D'Angelo, Egidio

    2008-01-01

    Around half of the neurons of a human brain are granule cells (approximately 10(11)granule neurons) [Kandel, E.R., Schwartz, J.H., Jessell, T.M., 2000. Principles of Neural Science. McGraw-Hill Professional Publishing, New York]. In order to study in detail the functional role of the intrinsic features of this cell we have developed a pre-compiled behavioural model based on the simplified granule-cell model of Bezzi et al. [Bezzi, M., Nieus, T., Arleo, A., D'Angelo, E., Coenen, O.J.-M.D., 2004. Information transfer at the mossy fiber-granule cell synapse of the cerebellum. 34th Annual Meeting. Society for Neuroscience, San Diego, CA, USA]. We can use an efficient event-driven simulation scheme based on lookup tables (EDLUT) [Ros, E., Carrillo, R.R., Ortigosa, E.M., Barbour, B., Ags, R., 2006. Event-driven simulation scheme for spiking neural networks using lookup tables to characterize neuronal dynamics. Neural Computation 18 (12), 2959-2993]. For this purpose it is necessary to compile into tables the data obtained through a massive numerical calculation of the simplified cell model. This allows network simulations requiring minimal numerical calculation. There are three major features that are considered functionally relevant in the simplified granule cell model: bursting, subthreshold oscillations and resonance. In this work we describe how the cell model is compiled into tables keeping these key properties of the neuron model.

  3. High-level simulation of JWST event-driven operations

    NASA Astrophysics Data System (ADS)

    Henry, R.; Kinzel, W.

    2012-09-01

    The James Webb Space Telescope (JWST) has an event-driven architecture: an onboard Observation Plan Executive (OPE) executes an Observation Plan (OP) consisting of a sequence of observing units (visits). During normal operations, ground action to update the OP is only expected to be necessary about once a week. This architecture is designed to tolerate uncertainty in visit duration, and occasional visit failures due to inability to acquire guide stars, without creating gaps in the observing timeline. The operations concept is complicated by the need for occasional scheduling of timecritical science and engineering visits that cannot tolerate much slippage without inducing gaps, and also by onboard momentum management. A prototype Python tool called the JWST Observation Plan Execution Simulator (JOPES) has recently been developed to simulate OP execution at a high level and analyze the response of the Observatory and OPE to both nominal and contingency scenarios. Incorporating both deterministic and stochastic behavior, JOPES has potential to be a powerful tool for several purposes: requirements analysis, system verification, systems engineering studies, and test data generation. It has already been successfully applied to a study of overhead estimation bias: whether to use conservative or average-case estimates for timing components that are inherently uncertain, such as those involving guide-star acquisition. JOPES is being enhanced to support interfaces to the operational Proposal Planning Subsystem (PPS) now being developed, with the objective of "closing the loop" between testing and simulation by feeding simulated event logs back into the PPS.

  4. Cellular Dynamic Simulator: An Event Driven Molecular Simulation Environment for Cellular Physiology

    PubMed Central

    Byrne, Michael J.; Waxham, M. Neal; Kubota, Yoshihisa

    2010-01-01

    In this paper, we present the Cellular Dynamic Simulator (CDS) for simulating diffusion and chemical reactions within crowded molecular environments. CDS is based on a novel event driven algorithm specifically designed for precise calculation of the timing of collisions, reactions and other events for each individual molecule in the environment. Generic mesh based compartments allow the creation / importation of very simple or detailed cellular structures that exist in a 3D environment. Multiple levels of compartments and static obstacles can be used to create a dense environment to mimic cellular boundaries and the intracellular space. The CDS algorithm takes into account volume exclusion and molecular crowding that may impact signaling cascades in small sub-cellular compartments such as dendritic spines. With the CDS, we can simulate simple enzyme reactions; aggregation, channel transport, as well as highly complicated chemical reaction networks of both freely diffusing and membrane bound multi-protein complexes. Components of the CDS are generally defined such that the simulator can be applied to a wide range of environments in terms of scale and level of detail. Through an initialization GUI, a simple simulation environment can be created and populated within minutes yet is powerful enough to design complex 3D cellular architecture. The initialization tool allows visual confirmation of the environment construction prior to execution by the simulator. This paper describes the CDS algorithm, design implementation, and provides an overview of the types of features available and the utility of those features are highlighted in demonstrations. PMID:20361275

  5. Cellular dynamic simulator: an event driven molecular simulation environment for cellular physiology.

    PubMed

    Byrne, Michael J; Waxham, M Neal; Kubota, Yoshihisa

    2010-06-01

    In this paper, we present the Cellular Dynamic Simulator (CDS) for simulating diffusion and chemical reactions within crowded molecular environments. CDS is based on a novel event driven algorithm specifically designed for precise calculation of the timing of collisions, reactions and other events for each individual molecule in the environment. Generic mesh based compartments allow the creation / importation of very simple or detailed cellular structures that exist in a 3D environment. Multiple levels of compartments and static obstacles can be used to create a dense environment to mimic cellular boundaries and the intracellular space. The CDS algorithm takes into account volume exclusion and molecular crowding that may impact signaling cascades in small sub-cellular compartments such as dendritic spines. With the CDS, we can simulate simple enzyme reactions; aggregation, channel transport, as well as highly complicated chemical reaction networks of both freely diffusing and membrane bound multi-protein complexes. Components of the CDS are generally defined such that the simulator can be applied to a wide range of environments in terms of scale and level of detail. Through an initialization GUI, a simple simulation environment can be created and populated within minutes yet is powerful enough to design complex 3D cellular architecture. The initialization tool allows visual confirmation of the environment construction prior to execution by the simulator. This paper describes the CDS algorithm, design implementation, and provides an overview of the types of features available and the utility of those features are highlighted in demonstrations.

  6. Simulating large-scale pedestrian movement using CA and event driven model: Methodology and case study

    NASA Astrophysics Data System (ADS)

    Li, Jun; Fu, Siyao; He, Haibo; Jia, Hongfei; Li, Yanzhong; Guo, Yi

    2015-11-01

    Large-scale regional evacuation is an important part of national security emergency response plan. Large commercial shopping area, as the typical service system, its emergency evacuation is one of the hot research topics. A systematic methodology based on Cellular Automata with the Dynamic Floor Field and event driven model has been proposed, and the methodology has been examined within context of a case study involving the evacuation within a commercial shopping mall. Pedestrians walking is based on Cellular Automata and event driven model. In this paper, the event driven model is adopted to simulate the pedestrian movement patterns, the simulation process is divided into normal situation and emergency evacuation. The model is composed of four layers: environment layer, customer layer, clerk layer and trajectory layer. For the simulation of movement route of pedestrians, the model takes into account purchase intention of customers and density of pedestrians. Based on evacuation model of Cellular Automata with Dynamic Floor Field and event driven model, we can reflect behavior characteristics of customers and clerks at the situations of normal and emergency evacuation. The distribution of individual evacuation time as a function of initial positions and the dynamics of the evacuation process is studied. Our results indicate that the evacuation model using the combination of Cellular Automata with Dynamic Floor Field and event driven scheduling can be used to simulate the evacuation of pedestrian flows in indoor areas with complicated surroundings and to investigate the layout of shopping mall.

  7. An Event-Driven Hybrid Molecular Dynamics and Direct Simulation Monte Carlo Algorithm

    SciTech Connect

    Donev, A; Garcia, A L; Alder, B J

    2007-07-30

    A novel algorithm is developed for the simulation of polymer chains suspended in a solvent. The polymers are represented as chains of hard spheres tethered by square wells and interact with the solvent particles with hard core potentials. The algorithm uses event-driven molecular dynamics (MD) for the simulation of the polymer chain and the interactions between the chain beads and the surrounding solvent particles. The interactions between the solvent particles themselves are not treated deterministically as in event-driven algorithms, rather, the momentum and energy exchange in the solvent is determined stochastically using the Direct Simulation Monte Carlo (DSMC) method. The coupling between the solvent and the solute is consistently represented at the particle level, however, unlike full MD simulations of both the solvent and the solute, the spatial structure of the solvent is ignored. The algorithm is described in detail and applied to the study of the dynamics of a polymer chain tethered to a hard wall subjected to uniform shear. The algorithm closely reproduces full MD simulations with two orders of magnitude greater efficiency. Results do not confirm the existence of periodic (cycling) motion of the polymer chain.

  8. The Validity of Self-Initiated, Event-Driven Infectious Disease Reporting in General Population Cohorts

    PubMed Central

    Merk, Hanna; Kühlmann-Berenzon, Sharon; Bexelius, Christin; Sandin, Sven; Litton, Jan-Eric; Linde, Annika; Nyrén, Olof

    2013-01-01

    Background The 2009/2010 pandemic influenza highlighted the need for valid and timely incidence data. In 2007 we started the development of a passive surveillance scheme based on passive follow-up of representative general population cohorts. Cohort members are asked to spontaneously report all instances of colds and fevers as soon as they occur for up to 9 months. Suspecting that compliance might be poor, we aimed to assess the validity of self-initiated, event-driven outcome reporting over long periods. Methods During two 8 week periods in 2008 and 2009, 2376 and 2514 cohort members in Stockholm County were sent one-week recall questionnaires, which served as reference method. Results The questionnaires were completed by 88% and 86% of the cohort members. Whilst the false positive proportion (1–specificity) in the reporting was low (upper bound of the 95% confidence interval [CI] ≤2% in each season), the false negative proportion (failure to report, 1–sensitivity) was considerable (60% [95% CI 52%–67%] in each season). Still, the resulting epidemic curves for influenza-like illness compared well with those from existing General Practitioner-based sentinel surveillance in terms of shape, timing of peak, and year-to-year variation. This suggested that the error was fairly constant. Conclusions Passive long-term surveillance through self-initiated, event-driven outcome reporting underestimates incidence rates of common upper respiratory tract infections. However, because underreporting appears predictable, simple corrections could potentially restore validity. PMID:23613891

  9. NEVESIM: event-driven neural simulation framework with a Python interface

    PubMed Central

    Pecevski, Dejan; Kappel, David; Jonke, Zeno

    2014-01-01

    NEVESIM is a software package for event-driven simulation of networks of spiking neurons with a fast simulation core in C++, and a scripting user interface in the Python programming language. It supports simulation of heterogeneous networks with different types of neurons and synapses, and can be easily extended by the user with new neuron and synapse types. To enable heterogeneous networks and extensibility, NEVESIM is designed to decouple the simulation logic of communicating events (spikes) between the neurons at a network level from the implementation of the internal dynamics of individual neurons. In this paper we will present the simulation framework of NEVESIM, its concepts and features, as well as some aspects of the object-oriented design approaches and simulation strategies that were utilized to efficiently implement the concepts and functionalities of the framework. We will also give an overview of the Python user interface, its basic commands and constructs, and also discuss the benefits of integrating NEVESIM with Python. One of the valuable capabilities of the simulator is to simulate exactly and efficiently networks of stochastic spiking neurons from the recently developed theoretical framework of neural sampling. This functionality was implemented as an extension on top of the basic NEVESIM framework. Altogether, the intended purpose of the NEVESIM framework is to provide a basis for further extensions that support simulation of various neural network models incorporating different neuron and synapse types that can potentially also use different simulation strategies. PMID:25177291

  10. NEVESIM: event-driven neural simulation framework with a Python interface.

    PubMed

    Pecevski, Dejan; Kappel, David; Jonke, Zeno

    2014-01-01

    NEVESIM is a software package for event-driven simulation of networks of spiking neurons with a fast simulation core in C++, and a scripting user interface in the Python programming language. It supports simulation of heterogeneous networks with different types of neurons and synapses, and can be easily extended by the user with new neuron and synapse types. To enable heterogeneous networks and extensibility, NEVESIM is designed to decouple the simulation logic of communicating events (spikes) between the neurons at a network level from the implementation of the internal dynamics of individual neurons. In this paper we will present the simulation framework of NEVESIM, its concepts and features, as well as some aspects of the object-oriented design approaches and simulation strategies that were utilized to efficiently implement the concepts and functionalities of the framework. We will also give an overview of the Python user interface, its basic commands and constructs, and also discuss the benefits of integrating NEVESIM with Python. One of the valuable capabilities of the simulator is to simulate exactly and efficiently networks of stochastic spiking neurons from the recently developed theoretical framework of neural sampling. This functionality was implemented as an extension on top of the basic NEVESIM framework. Altogether, the intended purpose of the NEVESIM framework is to provide a basis for further extensions that support simulation of various neural network models incorporating different neuron and synapse types that can potentially also use different simulation strategies.

  11. Hard Sphere Simulation by Event-Driven Molecular Dynamics: Breakthrough, Numerical Difficulty, and Overcoming the issues

    NASA Astrophysics Data System (ADS)

    Isobe, Masaharu

    Hard sphere/disk systems are among the simplest models and have been used to address numerous fundamental problems in the field of statistical physics. The pioneering numerical works on the solid-fluid phase transition based on Monte Carlo (MC) and molecular dynamics (MD) methods published in 1957 represent historical milestones, which have had a significant influence on the development of computer algorithms and novel tools to obtain physical insights. This chapter addresses the works of Alder's breakthrough regarding hard sphere/disk simulation: (i) event-driven molecular dynamics, (ii) long-time tail, (iii) molasses tail, and (iv) two-dimensional melting/crystallization. From a numerical viewpoint, there are serious issues that must be overcome for further breakthrough. Here, we present a brief review of recent progress in this area.

  12. Three-Dimensional Event-Driven Hybrid Simulations of Magnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Omelchenko, Y. A.; Karimabadi, H.; Vu, H. X.

    2012-12-01

    Existing space weather frameworks are based on global fluid models of the magnetosphere. However, a mature model of the coupling between regions and the global response of geospace to solar variations requires global kinetic-scale simulations. One reason for this is that most critical plasma processes regulating mass and energy transfer in the magnetosphere take place at relatively thin ion scale boundaries/discontinuities (e.g., bow shock, magnetopause, magnetotail) where ions control the essential physics. The region between these boundaries is also permeated with multiple ion species and ion-scale waves. Since fully kinetic (kinetic electrons and ions) 3D global simulations will remain out of reach in the foreseeable future, hybrid simulations (electron fluid, kinetic ions) have long been considered the next phase in the global modeling of the magnetosphere. Largely varying time and length scales impose severe numerical constraints on global simulations with hybrid codes. To enable larger simulations we developed a unique, uni-dimensional asynchronous (event-driven) hybrid code, HYPERS. Here we report preliminary results from first, 3D, parallel, asynchronous simulations of magnetized plasmas conducted with this new code.

  13. Slip velocity and stresses in granular Poiseuille flow via event-driven simulation.

    PubMed

    Chikkadi, Vijayakumar; Alam, Meheboob

    2009-08-01

    Event-driven simulations of inelastic smooth hard disks are used to probe the slip velocity and rheology in gravity-driven granular Poiseuille flow. It is shown that both the slip velocity (U(w)) and its gradient (dU(w)/dy) depend crucially on the mean density, wall roughness, and inelastic dissipation. While the gradient of slip velocity follows a single power-law relation with Knudsen number, the variation in U(w) with Kn shows three distinct regimes in terms of Knudsen number. An interesting possibility of Knudsen-number-dependent specularity coefficient emerges from a comparison of our results with a first-order transport theory for the slip velocity. Simulation results on stresses are compared with kinetic-theory predictions, with reasonable agreement of our data in the quasielastic limit. The deviation of simulations from theory increases with increasing dissipation which is tied to the increasing magnitude of the first normal stress difference (N(1)) that shows interesting nonmonotonic behavior with density. As in simple shear flow, there is a sign change of N(1) at some critical density and its collisional component and the related collisional anisotropy are responsible for this sign reversal.

  14. Efficient event-driven simulations shed new light on microtubule organization in the plant cortical array

    NASA Astrophysics Data System (ADS)

    Tindemans, Simon H.; Deinum, Eva E.; Lindeboom, Jelmer J.; Mulder, Bela M.

    2014-04-01

    The dynamics of the plant microtubule cytoskeleton is a paradigmatic example of the complex spatiotemporal processes characterising life at the cellular scale. This system is composed of large numbers of spatially extended particles, each endowed with its own intrinsic stochastic dynamics, and is capable of non-equilibrium self-organisation through collisional interactions of these particles. To elucidate the behaviour of such a complex system requires not only conceptual advances, but also the development of appropriate computational tools to simulate it. As the number of parameters involved is large and the behaviour is stochastic, it is essential that these simulations be fast enough to allow for an exploration of the phase space and the gathering of sufficient statistics to accurately pin down the average behaviour as well as the magnitude of fluctuations around it. Here we describe a simulation approach that meets this requirement by adopting an event-driven methodology that encompasses both the spontaneous stochastic changes in microtubule state as well as the deterministic collisions. In contrast with finite time step simulations this technique is intrinsically exact, as well as several orders of magnitude faster, which enables ordinary PC hardware to simulate systems of ˜ 10^3 microtubules on a time scale ˜ 10^{3} faster than real time. In addition we present new tools for the analysis of microtubule trajectories on curved surfaces. We illustrate the use of these methods by addressing a number of outstanding issues regarding the importance of various parameters on the transition from an isotropic to an aligned and oriented state.

  15. Teleradiology system analysis using a discrete event-driven block-oriented network simulator

    NASA Astrophysics Data System (ADS)

    Stewart, Brent K.; Dwyer, Samuel J., III

    1992-07-01

    Performance evaluation and trade-off analysis are the central issues in the design of communication networks. Simulation plays an important role in computer-aided design and analysis of communication networks and related systems, allowing testing of numerous architectural configurations and fault scenarios. We are using the Block Oriented Network Simulator (BONeS, Comdisco, Foster City, CA) software package to perform discrete, event- driven Monte Carlo simulations in capacity planning, tradeoff analysis and evaluation of alternate architectures for a high-speed, high-resolution teleradiology project. A queuing network model of the teleradiology system has been devise, simulations executed and results analyzed. The wide area network link uses a switched, dial-up N X 56 kbps inverting multiplexer where the number of digital voice-grade lines (N) can vary from one (DS-0) through 24 (DS-1). The proposed goal of such a system is 200 films (2048 X 2048 X 12-bit) transferred between a remote and local site in an eight hour period with a mean delay time less than five minutes. It is found that: (1) the DS-1 service limit is around 100 films per eight hour period with a mean delay time of 412 +/- 39 seconds, short of the goal stipulated above; (2) compressed video teleconferencing can be run simultaneously with image data transfer over the DS-1 wide area network link without impacting the performance of the described teleradiology system; (3) there is little sense in upgrading to a higher bandwidth WAN link like DS-2 or DS-3 for the current system; and (4) the goal of transmitting 200 films in an eight hour period with a mean delay time less than five minutes can be achieved simply if the laser printer interface is updated from the current DR-11W interface to a much faster SCSI interface.

  16. Comments on event driven animation

    NASA Technical Reports Server (NTRS)

    Gomez, Julian E.

    1987-01-01

    Event driven animation provides a general method of describing controlling values for various computer animation techniques. A definition and comments are provided on genralizing motion description with events. Additional comments are also provided about the implementation of twixt.

  17. A combined Event-Driven/Time-Driven molecular dynamics algorithm for the simulation of shock waves in rarefied gases

    SciTech Connect

    Valentini, Paolo Schwartzentruber, Thomas E.

    2009-12-10

    A novel combined Event-Driven/Time-Driven (ED/TD) algorithm to speed-up the Molecular Dynamics simulation of rarefied gases using realistic spherically symmetric soft potentials is presented. Due to the low density regime, the proposed method correctly identifies the time that must elapse before the next interaction occurs, similarly to Event-Driven Molecular Dynamics. However, each interaction is treated using Time-Driven Molecular Dynamics, thereby integrating Newton's Second Law using the sufficiently small time step needed to correctly resolve the atomic motion. Although infrequent, many-body interactions are also accounted for with a small approximation. The combined ED/TD method is shown to correctly reproduce translational relaxation in argon, described using the Lennard-Jones potential. For densities between {rho}=10{sup -4}kg/m{sup 3} and {rho}=10{sup -1}kg/m{sup 3}, comparisons with kinetic theory, Direct Simulation Monte Carlo, and pure Time-Driven Molecular Dynamics demonstrate that the ED/TD algorithm correctly reproduces the proper collision rates and the evolution toward thermal equilibrium. Finally, the combined ED/TD algorithm is applied to the simulation of a Mach 9 shock wave in rarefied argon. Density and temperature profiles as well as molecular velocity distributions accurately match DSMC results, and the shock thickness is within the experimental uncertainty. For the problems considered, the ED/TD algorithm ranged from several hundred to several thousand times faster than conventional Time-Driven MD. Moreover, the force calculation to integrate the molecular trajectories is found to contribute a negligible amount to the overall ED/TD simulation time. Therefore, this method could pave the way for the application of much more refined and expensive interatomic potentials, either classical or first-principles, to Molecular Dynamics simulations of shock waves in rarefied gases, involving vibrational nonequilibrium and chemical reactivity.

  18. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-02-28

    We present in a unifying way the main components of three examples of asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel event-driven algorithm for Direct Simulation Monte Carlo (DSMC). Finally, we describe how to combine MD with DSMC in an event-driven framework, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  19. Anticipating the Chaotic Behaviour of Industrial Systems Based on Stochastic, Event-Driven Simulations

    NASA Astrophysics Data System (ADS)

    Bruzzone, Agostino G.; Revetria, Roberto; Simeoni, Simone; Viazzo, Simone; Orsoni, Alessandra

    2004-08-01

    In logistics and industrial production managers must deal with the impact of stochastic events to improve performances and reduce costs. In fact, production and logistics systems are generally designed considering some parameters as deterministically distributed. While this assumption is mostly used for preliminary prototyping, it is sometimes also retained during the final design stage, and especially for estimated parameters (i.e. Market Request). The proposed methodology can determine the impact of stochastic events in the system by evaluating the chaotic threshold level. Such an approach, based on the application of a new and innovative methodology, can be implemented to find the condition under which chaos makes the system become uncontrollable. Starting from problem identification and risk assessment, several classification techniques are used to carry out an effect analysis and contingency plan estimation. In this paper the authors illustrate the methodology with respect to a real industrial case: a production problem related to the logistics of distributed chemical processing.

  20. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-08-30

    We present, in a unifying way, the main components of three asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel stochastic molecular-dynamics algorithm that builds on the Direct Simulation Monte Carlo (DSMC). We explain how to effectively combine event-driven and classical time-driven handling, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  1. Event-driven simulation of the state institution activity for the service provision based on business processes

    NASA Astrophysics Data System (ADS)

    Kataev, M. Yu.; Loseva, N. V.; Mitsel, A. A.; Bulysheva, L. A.; Kozlov, S. V.

    2017-01-01

    The paper presents an approach, based on business processes, assessment and control of the state of the state institution, the social insurance Fund. The paper describes the application of business processes, such as items with clear measurable parameters that need to be determined, controlled and changed for management. The example of one of the business processes of the state institutions, which shows the ability to solve management tasks, is given. The authors of the paper demonstrate the possibility of applying the mathematical apparatus of imitative simulation for solving management tasks.

  2. Event-Driven Process Chains (EPC)

    NASA Astrophysics Data System (ADS)

    Mendling, Jan

    This chapter provides a comprehensive overview of Event-driven Process Chains (EPCs) and introduces a novel definition of EPC semantics. EPCs became popular in the 1990s as a conceptual business process modeling language in the context of reference modeling. Reference modeling refers to the documentation of generic business operations in a model such as service processes in the telecommunications sector, for example. It is claimed that reference models can be reused and adapted as best-practice recommendations in individual companies (see [230, 168, 229, 131, 400, 401, 446, 127, 362, 126]). The roots of reference modeling can be traced back to the Kölner Integrationsmodell (KIM) [146, 147] that was developed in the 1960s and 1970s. In the 1990s, the Institute of Information Systems (IWi) in Saarbrücken worked on a project with SAP to define a suitable business process modeling language to document the processes of the SAP R/3 enterprise resource planning system. There were two results from this joint effort: the definition of EPCs [210] and the documentation of the SAP system in the SAP Reference Model (see [92, 211]). The extensive database of this reference model contains almost 10,000 sub-models: 604 of them non-trivial EPC business process models. The SAP Reference model had a huge impact with several researchers referring to it in their publications (see [473, 235, 127, 362, 281, 427, 415]) as well as motivating the creation of EPC reference models in further domains including computer integrated manufacturing [377, 379], logistics [229] or retail [52]. The wide-spread application of EPCs in business process modeling theory and practice is supported by their coverage in seminal text books for business process management and information systems in general (see [378, 380, 49, 384, 167, 240]). EPCs are frequently used in practice due to a high user acceptance [376] and extensive tool support. Some examples of tools that support EPCs are ARIS Toolset by IDS

  3. Optimal switching policy for performance enhancement of distributed parameter systems based on event-driven control

    NASA Astrophysics Data System (ADS)

    Mu, Wen-Ying; Cui, Bao-Tong; Lou, Xu-Yang; Li, Wen

    2014-07-01

    This paper aims to improve the performance of a class of distributed parameter systems for the optimal switching of actuators and controllers based on event-driven control. It is assumed that in the available multiple actuators, only one actuator can receive the control signal and be activated over an unfixed time interval, and the other actuators keep dormant. After incorporating a state observer into the event generator, the event-driven control loop and the minimum inter-event time are ultimately bounded. Based on the event-driven state feedback control, the time intervals of unfixed length can be obtained. The optimal switching policy is based on finite horizon linear quadratic optimal control at the beginning of each time subinterval. A simulation example demonstrate the effectiveness of the proposed policy.

  4. The three-dimensional Event-Driven Graphics Environment (3D-EDGE)

    NASA Technical Reports Server (NTRS)

    Freedman, Jeffrey; Hahn, Roger; Schwartz, David M.

    1993-01-01

    Stanford Telecom developed the Three-Dimensional Event-Driven Graphics Environment (3D-EDGE) for NASA GSFC's (GSFC) Communications Link Analysis and Simulation System (CLASS). 3D-EDGE consists of a library of object-oriented subroutines which allow engineers with little or no computer graphics experience to programmatically manipulate, render, animate, and access complex three-dimensional objects.

  5. On Mixed Data and Event Driven Design for Adaptive-Critic-Based Nonlinear $H∞ Control.

    PubMed

    Wang, Ding; Mu, Chaoxu; Liu, Derong; Ma, Hongwen

    2017-02-01

    In this paper, based on the adaptive critic learning technique, the H∞ control for a class of unknown nonlinear dynamic systems is investigated by adopting a mixed data and event driven design approach. The nonlinear H∞ control problem is formulated as a two-player zero-sum differential game and the adaptive critic method is employed to cope with the data-based optimization. The novelty lies in that the data driven learning identifier is combined with the event driven design formulation, in order to develop the adaptive critic controller, thereby accomplishing the nonlinear H∞ control. The event driven optimal control law and the time driven worst case disturbance law are approximated by constructing and tuning a critic neural network. Applying the event driven feedback control, the closed-loop system is built with stability analysis. Simulation studies are conducted to verify the theoretical results and illustrate the control performance. It is significant to observe that the present research provides a new avenue of integrating data-based control and event-triggering mechanism into establishing advanced adaptive critic systems.

  6. Feasibility study for a generalized gate logic software simulator

    NASA Technical Reports Server (NTRS)

    Mcgough, J. G.

    1983-01-01

    Unit-delay simulation, event driven simulation, zero-delay simulation, simulation techniques, 2-valued versus multivalued logic, network initialization, gate operations and alternate network representations, parallel versus serial mode simulation fault modelling, extension of multiprocessor systems, and simulation timing are discussed. Functional level networks, gate equivalent circuits, the prototype BDX-930 network model, fault models, identifying detected faults for BGLOSS are discussed. Preprocessor tasks, postprocessor tasks, executive tasks, and a library of bliss coded macros for GGLOSS are also discussed.

  7. Asynchronous networks and event driven dynamics

    NASA Astrophysics Data System (ADS)

    Bick, Christian; Field, Michael

    2017-02-01

    Real-world networks in technology, engineering and biology often exhibit dynamics that cannot be adequately reproduced using network models given by smooth dynamical systems and a fixed network topology. Asynchronous networks give a theoretical and conceptual framework for the study of network dynamics where nodes can evolve independently of one another, be constrained, stop, and later restart, and where the interaction between different components of the network may depend on time, state, and stochastic effects. This framework is sufficiently general to encompass a wide range of applications ranging from engineering to neuroscience. Typically, dynamics is piecewise smooth and there are relationships with Filippov systems. In this paper, we give examples of asynchronous networks, and describe the basic formalism and structure. In the following companion paper, we make the notion of a functional asynchronous network rigorous, discuss the phenomenon of dynamical locks, and present a foundational result on the spatiotemporal factorization of the dynamics for a large class of functional asynchronous networks.

  8. Two-ball problem revisited: Limitations of event-driven modeling

    NASA Astrophysics Data System (ADS)

    Müller, Patric; Pöschel, Thorsten

    2011-04-01

    The main precondition of simulating systems of hard particles by means of event-driven modeling is the assumption of instantaneous collisions. The aim of this paper is to quantify the deviation of event-driven modeling from the solution of Newton’s equation of motion using a paradigmatic example: If a tennis ball is held above a basketball with their centers vertically aligned, and the balls are released to collide with the floor, the tennis ball may rebound at a surprisingly high speed. We show in this article that the simple textbook explanation of this effect is an oversimplification, even for the limit of perfectly elastic particles. Instead, there may occur a rather complex scenario including multiple collisions which may lead to a very different final velocity as compared with the velocity resulting from the oversimplified model.

  9. Two-ball problem revisited: limitations of event-driven modeling.

    PubMed

    Müller, Patric; Pöschel, Thorsten

    2011-04-01

    The main precondition of simulating systems of hard particles by means of event-driven modeling is the assumption of instantaneous collisions. The aim of this paper is to quantify the deviation of event-driven modeling from the solution of Newton's equation of motion using a paradigmatic example: If a tennis ball is held above a basketball with their centers vertically aligned, and the balls are released to collide with the floor, the tennis ball may rebound at a surprisingly high speed. We show in this article that the simple textbook explanation of this effect is an oversimplification, even for the limit of perfectly elastic particles. Instead, there may occur a rather complex scenario including multiple collisions which may lead to a very different final velocity as compared with the velocity resulting from the oversimplified model. ©2011 American Physical Society

  10. Event-Driven Random Back-Propagation: Enabling Neuromorphic Deep Learning Machines

    PubMed Central

    Neftci, Emre O.; Augustine, Charles; Paul, Somnath; Detorakis, Georgios

    2017-01-01

    An ongoing challenge in neuromorphic computing is to devise general and computationally efficient models of inference and learning which are compatible with the spatial and temporal constraints of the brain. One increasingly popular and successful approach is to take inspiration from inference and learning algorithms used in deep neural networks. However, the workhorse of deep learning, the gradient descent Gradient Back Propagation (BP) rule, often relies on the immediate availability of network-wide information stored with high-precision memory during learning, and precise operations that are difficult to realize in neuromorphic hardware. Remarkably, recent work showed that exact backpropagated gradients are not essential for learning deep representations. Building on these results, we demonstrate an event-driven random BP (eRBP) rule that uses an error-modulated synaptic plasticity for learning deep representations. Using a two-compartment Leaky Integrate & Fire (I&F) neuron, the rule requires only one addition and two comparisons for each synaptic weight, making it very suitable for implementation in digital or mixed-signal neuromorphic hardware. Our results show that using eRBP, deep representations are rapidly learned, achieving classification accuracies on permutation invariant datasets comparable to those obtained in artificial neural network simulations on GPUs, while being robust to neural and synaptic state quantizations during learning. PMID:28680387

  11. Event-Driven Random Back-Propagation: Enabling Neuromorphic Deep Learning Machines.

    PubMed

    Neftci, Emre O; Augustine, Charles; Paul, Somnath; Detorakis, Georgios

    2017-01-01

    An ongoing challenge in neuromorphic computing is to devise general and computationally efficient models of inference and learning which are compatible with the spatial and temporal constraints of the brain. One increasingly popular and successful approach is to take inspiration from inference and learning algorithms used in deep neural networks. However, the workhorse of deep learning, the gradient descent Gradient Back Propagation (BP) rule, often relies on the immediate availability of network-wide information stored with high-precision memory during learning, and precise operations that are difficult to realize in neuromorphic hardware. Remarkably, recent work showed that exact backpropagated gradients are not essential for learning deep representations. Building on these results, we demonstrate an event-driven random BP (eRBP) rule that uses an error-modulated synaptic plasticity for learning deep representations. Using a two-compartment Leaky Integrate & Fire (I&F) neuron, the rule requires only one addition and two comparisons for each synaptic weight, making it very suitable for implementation in digital or mixed-signal neuromorphic hardware. Our results show that using eRBP, deep representations are rapidly learned, achieving classification accuracies on permutation invariant datasets comparable to those obtained in artificial neural network simulations on GPUs, while being robust to neural and synaptic state quantizations during learning.

  12. 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…

  13. Event management for large scale event-driven digital hardware spiking neural networks.

    PubMed

    Caron, Louis-Charles; D'Haene, Michiel; Mailhot, Frédéric; Schrauwen, Benjamin; Rouat, Jean

    2013-09-01

    The interest in brain-like computation has led to the design of a plethora of innovative neuromorphic systems. Individually, spiking neural networks (SNNs), event-driven simulation and digital hardware neuromorphic systems get a lot of attention. Despite the popularity of event-driven SNNs in software, very few digital hardware architectures are found. This is because existing hardware solutions for event management scale badly with the number of events. This paper introduces the structured heap queue, a pipelined digital hardware data structure, and demonstrates its suitability for event management. The structured heap queue scales gracefully with the number of events, allowing the efficient implementation of large scale digital hardware event-driven SNNs. The scaling is linear for memory, logarithmic for logic resources and constant for processing time. The use of the structured heap queue is demonstrated on a field-programmable gate array (FPGA) with an image segmentation experiment and a SNN of 65,536 neurons and 513,184 synapses. Events can be processed at the rate of 1 every 7 clock cycles and a 406×158 pixel image is segmented in 200 ms. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Automatic Distribution Network Reconfiguration: An Event-Driven Approach

    SciTech Connect

    Ding, Fei; Jiang, Huaiguang; Tan, Jin

    2016-11-14

    This paper proposes an event-driven approach for reconfiguring distribution systems automatically. Specifically, an optimal synchrophasor sensor placement (OSSP) is used to reduce the number of synchrophasor sensors while keeping the whole system observable. Then, a wavelet-based event detection and location approach is used to detect and locate the event, which performs as a trigger for network reconfiguration. With the detected information, the system is then reconfigured using the hierarchical decentralized approach to seek for the new optimal topology. In this manner, whenever an event happens the distribution network can be reconfigured automatically based on the real-time information that is observable and detectable.

  15. Intelligent fuzzy controller for event-driven real time systems

    NASA Technical Reports Server (NTRS)

    Grantner, Janos; Patyra, Marek; Stachowicz, Marian S.

    1992-01-01

    Most of the known linguistic models are essentially static, that is, time is not a parameter in describing the behavior of the object's model. In this paper we show a model for synchronous finite state machines based on fuzzy logic. Such finite state machines can be used to build both event-driven, time-varying, rule-based systems and the control unit section of a fuzzy logic computer. The architecture of a pipelined intelligent fuzzy controller is presented, and the linguistic model is represented by an overall fuzzy relation stored in a single rule memory. A VLSI integrated circuit implementation of the fuzzy controller is suggested. At a clock rate of 30 MHz, the controller can perform 3 MFLIPS on multi-dimensional fuzzy data.

  16. Multirate and event-driven Kalman filters for helicopter flight

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Smith, Phillip; Suorsa, Raymond E.; Hussien, Bassam

    1993-01-01

    A vision-based obstacle detection system that provides information about objects as a function of azimuth and elevation is discussed. The range map is computed using a sequence of images from a passive sensor, and an extended Kalman filter is used to estimate range to obstacles. The magnitude of the optical flow that provides measurements for each Kalman filter varies significantly over the image depending on the helicopter motion and object location. In a standard Kalman filter, the measurement update takes place at fixed intervals. It may be necessary to use a different measurement update rate in different parts of the image in order to maintain the same signal to noise ratio in the optical flow calculations. A range estimation scheme that accepts the measurement only under certain conditions is presented. The estimation results from the standard Kalman filter are compared with results from a multirate Kalman filter and an event-driven Kalman filter for a sequence of helicopter flight images.

  17. A Full Parallel Event Driven Readout Technique for Area Array SPAD FLIM Image Sensors

    PubMed Central

    Nie, Kaiming; Wang, Xinlei; Qiao, Jun; Xu, Jiangtao

    2016-01-01

    This paper presents a full parallel event driven readout method which is implemented in an area array single-photon avalanche diode (SPAD) image sensor for high-speed fluorescence lifetime imaging microscopy (FLIM). The sensor only records and reads out effective time and position information by adopting full parallel event driven readout method, aiming at reducing the amount of data. The image sensor includes four 8 × 8 pixel arrays. In each array, four time-to-digital converters (TDCs) are used to quantize the time of photons’ arrival, and two address record modules are used to record the column and row information. In this work, Monte Carlo simulations were performed in Matlab in terms of the pile-up effect induced by the readout method. The sensor’s resolution is 16 × 16. The time resolution of TDCs is 97.6 ps and the quantization range is 100 ns. The readout frame rate is 10 Mfps, and the maximum imaging frame rate is 100 fps. The chip’s output bandwidth is 720 MHz with an average power of 15 mW. The lifetime resolvability range is 5–20 ns, and the average error of estimated fluorescence lifetimes is below 1% by employing CMM to estimate lifetimes. PMID:26828490

  18. Stochastic Optimal Regulation of Nonlinear Networked Control Systems by Using Event-Driven Adaptive Dynamic Programming.

    PubMed

    Sahoo, Avimanyu; Jagannathan, Sarangapani

    2017-02-01

    In this paper, an event-driven stochastic adaptive dynamic programming (ADP)-based technique is introduced for nonlinear systems with a communication network within its feedback loop. A near optimal control policy is designed using an actor-critic framework and ADP with event sampled state vector. First, the system dynamics are approximated by using a novel neural network (NN) identifier with event sampled state vector. The optimal control policy is generated via an actor NN by using the NN identifier and value function approximated by a critic NN through ADP. The stochastic NN identifier, actor, and critic NN weights are tuned at the event sampled instants leading to aperiodic weight tuning laws. Above all, an adaptive event sampling condition based on estimated NN weights is designed by using the Lyapunov technique to ensure ultimate boundedness of all the closed-loop signals along with the approximation accuracy. The net result is event-driven stochastic ADP technique that can significantly reduce the computation and network transmissions. Finally, the analytical design is substantiated with simulation results.

  19. General Purpose Heat Source Simulator

    NASA Technical Reports Server (NTRS)

    Emrich, William J., Jr.

    2008-01-01

    The General Purpose Heat Source (GPHS) project seeks to combine the development of an electrically heated, single GPHS module simulator with the evaluation of potential nuclear surface power systems. The simulator is designed to match the form, fit, and function of actual GPHS modules which normally generate heat through the radioactive decay of Pu238. The use of electrically heated modules rather than modules containing Pu238 facilitates the testing of the subsystems and systems without sacrificing the quantity and quality of the test data gathered. Current GPHS activities are centered on developing robust heater designs with sizes and weights which closely match those of actual Pu238 fueled GPHS blocks. Designs are being pursued which will allow operation up to 1100 C.

  20. Event-Driven Random-Access-Windowing CCD Imaging System

    NASA Technical Reports Server (NTRS)

    Monacos, Steve; Portillo, Angel; Ortiz, Gerardo; Alexander, James; Lam, Raymond; Liu, William

    2004-01-01

    A charge-coupled-device (CCD) based high-speed imaging system, called a realtime, event-driven (RARE) camera, is undergoing development. This camera is capable of readout from multiple subwindows [also known as regions of interest (ROIs)] within the CCD field of view. Both the sizes and the locations of the ROIs can be controlled in real time and can be changed at the camera frame rate. The predecessor of this camera was described in High-Frame-Rate CCD Camera Having Subwindow Capability (NPO- 30564) NASA Tech Briefs, Vol. 26, No. 12 (December 2002), page 26. The architecture of the prior camera requires tight coupling between camera control logic and an external host computer that provides commands for camera operation and processes pixels from the camera. This tight coupling limits the attainable frame rate and functionality of the camera. The design of the present camera loosens this coupling to increase the achievable frame rate and functionality. From a host computer perspective, the readout operation in the prior camera was defined on a per-line basis; in this camera, it is defined on a per-ROI basis. In addition, the camera includes internal timing circuitry. This combination of features enables real-time, event-driven operation for adaptive control of the camera. Hence, this camera is well suited for applications requiring autonomous control of multiple ROIs to track multiple targets moving throughout the CCD field of view. Additionally, by eliminating the need for control intervention by the host computer during the pixel readout, the present design reduces ROI-readout times to attain higher frame rates. This camera (see figure) includes an imager card consisting of a commercial CCD imager and two signal-processor chips. The imager card converts transistor/ transistor-logic (TTL)-level signals from a field programmable gate array (FPGA) controller card. These signals are transmitted to the imager card via a low-voltage differential signaling (LVDS) cable

  1. Event Driven Messaging with Role-Based Subscriptions

    NASA Technical Reports Server (NTRS)

    Bui, Tung; Bui, Bach; Malhotra, Shantanu; Chen, Fannie; Kim, rachel; Allen, Christopher; Luong, Ivy; Chang, George; Zendejas, Silvino; Sadaqathulla, Syed

    2009-01-01

    Event Driven Messaging with Role-Based Subscriptions (EDM-RBS) is a framework integrated into the Service Management Database (SMDB) to allow for role-based and subscription-based delivery of synchronous and asynchronous messages over JMS (Java Messaging Service), SMTP (Simple Mail Transfer Protocol), or SMS (Short Messaging Service). This allows for 24/7 operation with users in all parts of the world. The software classifies messages by triggering data type, application source, owner of data triggering event (mission), classification, sub-classification and various other secondary classifying tags. Messages are routed to applications or users based on subscription rules using a combination of the above message attributes. This program provides a framework for identifying connected users and their applications for targeted delivery of messages over JMS to the client applications the user is logged into. EDMRBS provides the ability to send notifications over e-mail or pager rather than having to rely on a live human to do it. It is implemented as an Oracle application that uses Oracle relational database management system intrinsic functions. It is configurable to use Oracle AQ JMS API or an external JMS provider for messaging. It fully integrates into the event-logging framework of SMDB (Subnet Management Database).

  2. Event-driven contrastive divergence for spiking neuromorphic systems

    PubMed Central

    Neftci, Emre; Das, Srinjoy; Pedroni, Bruno; Kreutz-Delgado, Kenneth; Cauwenberghs, Gert

    2014-01-01

    Restricted Boltzmann Machines (RBMs) and Deep Belief Networks have been demonstrated to perform efficiently in a variety of applications, such as dimensionality reduction, feature learning, and classification. Their implementation on neuromorphic hardware platforms emulating large-scale networks of spiking neurons can have significant advantages from the perspectives of scalability, power dissipation and real-time interfacing with the environment. However, the traditional RBM architecture and the commonly used training algorithm known as Contrastive Divergence (CD) are based on discrete updates and exact arithmetics which do not directly map onto a dynamical neural substrate. Here, we present an event-driven variation of CD to train a RBM constructed with Integrate & Fire (I&F) neurons, that is constrained by the limitations of existing and near future neuromorphic hardware platforms. Our strategy is based on neural sampling, which allows us to synthesize a spiking neural network that samples from a target Boltzmann distribution. The recurrent activity of the network replaces the discrete steps of the CD algorithm, while Spike Time Dependent Plasticity (STDP) carries out the weight updates in an online, asynchronous fashion. We demonstrate our approach by training an RBM composed of leaky I&F neurons with STDP synapses to learn a generative model of the MNIST hand-written digit dataset, and by testing it in recognition, generation and cue integration tasks. Our results contribute to a machine learning-driven approach for synthesizing networks of spiking neurons capable of carrying out practical, high-level functionality. PMID:24574952

  3. Event-driven contrastive divergence for spiking neuromorphic systems.

    PubMed

    Neftci, Emre; Das, Srinjoy; Pedroni, Bruno; Kreutz-Delgado, Kenneth; Cauwenberghs, Gert

    2013-01-01

    Restricted Boltzmann Machines (RBMs) and Deep Belief Networks have been demonstrated to perform efficiently in a variety of applications, such as dimensionality reduction, feature learning, and classification. Their implementation on neuromorphic hardware platforms emulating large-scale networks of spiking neurons can have significant advantages from the perspectives of scalability, power dissipation and real-time interfacing with the environment. However, the traditional RBM architecture and the commonly used training algorithm known as Contrastive Divergence (CD) are based on discrete updates and exact arithmetics which do not directly map onto a dynamical neural substrate. Here, we present an event-driven variation of CD to train a RBM constructed with Integrate & Fire (I&F) neurons, that is constrained by the limitations of existing and near future neuromorphic hardware platforms. Our strategy is based on neural sampling, which allows us to synthesize a spiking neural network that samples from a target Boltzmann distribution. The recurrent activity of the network replaces the discrete steps of the CD algorithm, while Spike Time Dependent Plasticity (STDP) carries out the weight updates in an online, asynchronous fashion. We demonstrate our approach by training an RBM composed of leaky I&F neurons with STDP synapses to learn a generative model of the MNIST hand-written digit dataset, and by testing it in recognition, generation and cue integration tasks. Our results contribute to a machine learning-driven approach for synthesizing networks of spiking neurons capable of carrying out practical, high-level functionality.

  4. A Hybrid Adaptive Routing Algorithm for Event-Driven Wireless Sensor Networks

    PubMed Central

    Figueiredo, Carlos M. S.; Nakamura, Eduardo F.; Loureiro, Antonio A. F.

    2009-01-01

    Routing is a basic function in wireless sensor networks (WSNs). For these networks, routing algorithms depend on the characteristics of the applications and, consequently, there is no self-contained algorithm suitable for every case. In some scenarios, the network behavior (traffic load) may vary a lot, such as an event-driven application, favoring different algorithms at different instants. This work presents a hybrid and adaptive algorithm for routing in WSNs, called Multi-MAF, that adapts its behavior autonomously in response to the variation of network conditions. In particular, the proposed algorithm applies both reactive and proactive strategies for routing infrastructure creation, and uses an event-detection estimation model to change between the strategies and save energy. To show the advantages of the proposed approach, it is evaluated through simulations. Comparisons with independent reactive and proactive algorithms show improvements on energy consumption. PMID:22423207

  5. Multiagent Attitude Control System for Satellites Based in Momentum Wheels and Event-Driven Synchronization

    NASA Astrophysics Data System (ADS)

    Garcia, Juan L.; Moreno, Jose Sanchez

    2012-12-01

    Attitude control is a requirement always present in spacecraft design. Several kinds of actuators exist to accomplish this control, being momentum wheels one of the most employed. Usually satellites carry redundant momentum wheels to handle any possible single failure, but the controller remains as a single centralized element, posing problems in case of failures. In this work a decentralized agent-based event-driven algorithm for attitude control is presented as a possible solution. Several agents based in momentum wheels will interact among them to accomplish the satellite control. A simulation environment has been developed to analyze the behavior of this architecture. This environment has been made available through the web page http://www.dia.uned.es.

  6. General Purpose Heat Source Simulator

    NASA Technical Reports Server (NTRS)

    Emrich, Bill

    2008-01-01

    The General Purpose Heat Source (GPHS) simulator project is designed to replicate through the use of electrical heaters, the form, fit, and function of actual GPHS modules which generate heat through the radioactive decay of Pu238. The use of electrically heated modules rather than modules containing Pu238 facilitates the testing of spacecraft subsystems and systems without sacrificing the quantity and quality of the test data gathered. Previous GPHS activities are centered around developing robust heater designs with sizes and weights that closely matched those of actual Pu238 fueled GPHS blocks. These efforts were successful, although their maximum temperature capabilities were limited to around 850 C. New designs are being pursued which also replicate the sizes and weights of actual Pu238 fueled GPHS blocks but will allow operation up to 1100 C.

  7. General Purpose Heat Source Simulator

    NASA Technical Reports Server (NTRS)

    Emrich, Bill

    2008-01-01

    The General Purpose Heat Source (GPHS) simulator project is designed to replicate through the use of electrical heaters, the form, fit, and function of actual GPHS modules which generate heat through the radioactive decay of Pu238. The use of electrically heated modules rather than modules containing Pu238 facilitates the testing of spacecraft subsystems and systems without sacrificing the quantity and quality of the test data gathered. Previous GPHS activities are centered around developing robust heater designs with sizes and weights that closely matched those of actual Pu238 fueled GPHS blocks. These efforts were successful, although their maximum temperature capabilities were limited to around 850 C. New designs are being pursued which also replicate the sizes and weights of actual Pu238 fueled GPHS blocks but will allow operation up to 1100 C.

  8. Mapping from frame-driven to frame-free event-driven vision systems by low-rate rate coding and coincidence processing--application to feedforward ConvNets.

    PubMed

    Pérez-Carrasco, José Antonio; Zhao, Bo; Serrano, Carmen; Acha, Begoña; Serrano-Gotarredona, Teresa; Chen, Shouchun; Linares-Barranco, Bernabé

    2013-11-01

    Event-driven visual sensors have attracted interest from a number of different research communities. They provide visual information in quite a different way from conventional video systems consisting of sequences of still images rendered at a given "frame rate." Event-driven vision sensors take inspiration from biology. Each pixel sends out an event (spike) when it senses something meaningful is happening, without any notion of a frame. A special type of event-driven sensor is the so-called dynamic vision sensor (DVS) where each pixel computes relative changes of light or "temporal contrast." The sensor output consists of a continuous flow of pixel events that represent the moving objects in the scene. Pixel events become available with microsecond delays with respect to "reality." These events can be processed "as they flow" by a cascade of event (convolution) processors. As a result, input and output event flows are practically coincident in time, and objects can be recognized as soon as the sensor provides enough meaningful events. In this paper, we present a methodology for mapping from a properly trained neural network in a conventional frame-driven representation to an event-driven representation. The method is illustrated by studying event-driven convolutional neural networks (ConvNet) trained to recognize rotating human silhouettes or high speed poker card symbols. The event-driven ConvNet is fed with recordings obtained from a real DVS camera. The event-driven ConvNet is simulated with a dedicated event-driven simulator and consists of a number of event-driven processing modules, the characteristics of which are obtained from individually manufactured hardware modules.

  9. Mapping from Frame-Driven to Frame-Free Event-Driven Vision Systems by Low-Rate Rate-Coding and Coincidence Processing. Application to Feed Forward ConvNets.

    PubMed

    Perez-Carrasco, J A; Zhao, B; Serrano, C; Acha, B; Serrano-Gotarredona, T; Chen, S; Linares-Barranco, B

    2013-04-10

    Event-driven visual sensors have attracted interest from a number of different research communities. They provide visual information in quite a different way from conventional video systems consisting of sequences of still images rendered at “frame rate”. Event-driven vision sensors take inspiration from biology. A special type of Event-driven sensor is the so called Dynamic-Vision-Sensor (DVS) where each pixel computes relative changes of light, or “temporal contrast”. Pixel events become available with micro second delays with respect to “reality”. These events can be processed “as they flow” by a cascade of event (convolution) processors. As a result, input and output event flows are practically coincident, and objects can be recognized as soon as the sensor provides enough meaningful events. In this paper we present a methodology for mapping from a properly trained neural network in a conventional Frame-driven representation, to an Event-driven representation. The method is illustrated by studying Event-driven Convolutional Neural Networks (ConvNet) trained to recognize rotating human silhouettes or high speed poker card symbols. The Event-driven ConvNet is fed with recordings obtained from a real DVS camera. The Event-driven ConvNet is simulated with a dedicated Event-driven simulator, and consists of a number of Event-driven processing modules the characteristics of which are obtained from individually manufactured hardware modules.

  10. An experimental, theoretical and event-driven computational study of narrow vibrofluidised granular materials

    NASA Astrophysics Data System (ADS)

    Thornton, Anthony; Windows-Yule, Kit; Parker, David; Luding, Stefan

    2017-06-01

    We review simulations, experiments and a theoretical treatment of vertically vibrated granular media. The systems considered are confined in narrow quasi-two-dimensional and quasi-one-dimensional (column) geometries, where the vertical extension of the container is much larger than one or both horizontal lengths. The additional geometric constraint present in the column setup frustrates the convection state that is normally observed in wider geometries. We start by showing that the Event Driven (ED) simulation method is able to accurately reproduce the previously experimentally determined phase-diagram for vibrofludised granular materials. We then review two papers that used ED simulations to study narrow quasi-one-dimensional systems revealing a new phenomenon: collective oscillations of the grains with a characteristic frequency that is much lower than the frequency of energy injection. Theoretical work was then undertaken that is able to accurately predict the frequency of such an oscillation and Positron Emission Particle Tracking (PEPT) experiments were undertaken to provide the first experimental evidence of this new phenomenon. Finally, we briefly discuss ongoing work to create an open-source version of this ED via its integration in the existing open-source package MercuryDPM (http://MercuryDPM.org); which has many advanced features that are not found in other codes.

  11. Event-Driven X-Ray CCD Detectors for High Energy Astrophysics

    NASA Technical Reports Server (NTRS)

    Ricker, George R.

    2004-01-01

    A viewgraph presentation describing the Event-Driven X- Ray CCD (EDCCD) detector system for high energy astrophysics is presented. The topics include: 1) EDCCD: Description and Advantages; 2) Summary of Grant Activity Carried Out; and 3) EDCCD Test System.

  12. Event-driven management algorithm of an Engineering documents circulation system

    NASA Astrophysics Data System (ADS)

    Kuzenkov, V.; Zebzeev, A.; Gromakov, E.

    2015-04-01

    Development methodology of an engineering documents circulation system in the design company is reviewed. Discrete event-driven automatic models using description algorithms of project management is offered. Petri net use for dynamic design of projects is offered.

  13. Exact event-driven implementation for recurrent networks of stochastic perfect integrate-and-fire neurons.

    PubMed

    Taillefumier, Thibaud; Touboul, Jonathan; Magnasco, Marcelo

    2012-12-01

    In vivo cortical recording reveals that indirectly driven neural assemblies can produce reliable and temporally precise spiking patterns in response to stereotyped stimulation. This suggests that despite being fundamentally noisy, the collective activity of neurons conveys information through temporal coding. Stochastic integrate-and-fire models delineate a natural theoretical framework to study the interplay of intrinsic neural noise and spike timing precision. However, there are inherent difficulties in simulating their networks' dynamics in silico with standard numerical discretization schemes. Indeed, the well-posedness of the evolution of such networks requires temporally ordering every neuronal interaction, whereas the order of interactions is highly sensitive to the random variability of spiking times. Here, we answer these issues for perfect stochastic integrate-and-fire neurons by designing an exact event-driven algorithm for the simulation of recurrent networks, with delayed Dirac-like interactions. In addition to being exact from the mathematical standpoint, our proposed method is highly efficient numerically. We envision that our algorithm is especially indicated for studying the emergence of polychronized motifs in networks evolving under spike-timing-dependent plasticity with intrinsic noise.

  14. Event-driven model predictive control of sewage pumping stations for sulfide mitigation in sewer networks.

    PubMed

    Liu, Yiqi; Ganigué, Ramon; Sharma, Keshab; Yuan, Zhiguo

    2016-07-01

    Chemicals such as Mg(OH)2 and iron salts are widely dosed to sewage for mitigating sulfide-induced corrosion and odour problems in sewer networks. The chemical dosing rate is usually not automatically controlled but profiled based on experience of operators, often resulting in over- or under-dosing. Even though on-line control algorithms for chemical dosing in single pipes have been developed recently, network-wide control algorithms are currently not available. The key challenge is that a sewer network is typically wide-spread comprising many interconnected sewer pipes and pumping stations, making network-wide sulfide mitigation with a relatively limited number of dosing points challenging. In this paper, we propose and demonstrate an Event-driven Model Predictive Control (EMPC) methodology, which controls the flows of sewage streams containing the dosed chemical to ensure desirable distribution of the dosed chemical throughout the pipe sections of interests. First of all, a network-state model is proposed to predict the chemical concentration in a network. An EMPC algorithm is then designed to coordinate sewage pumping station operations to ensure desirable chemical distribution in the network. The performance of the proposed control methodology is demonstrated by applying the designed algorithm to a real sewer network simulated with the well-established SeweX model using real sewage flow and characteristics data. The EMPC strategy significantly improved the sulfide mitigation performance with the same chemical consumption, compared to the current practice. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Field Evaluation of a General Purpose Simulator.

    ERIC Educational Resources Information Center

    Spangenberg, Ronald W.

    The use of a general purpose simulator (GPS) to teach Air Force technicians diagnostic and repair procedures for specialized aircraft radar systems is described. An EC II simulator manufactured by Educational Computer Corporation was adapted to resemble the actual configuration technicians would encounter in the field. Data acquired in the…

  16. Social-Event-Driven Camera Control for Multicharacter Animations.

    PubMed

    Yeh, I-Cheng; Lin, Wen-Chieh; Lee, Tong-Yee; Han, Hsin-Ju; Lee, Jehee; Kim, Manmyung

    2012-09-01

    In a virtual world, a group of virtual characters can interact with each other, and these characters may leave a group to join another. The interaction among individuals and groups often produces interesting events in a sequence of animation. The goal of this paper is to discover social events involving mutual interactions or group activities in multicharacter animations and automatically plan a smooth camera motion to view interesting events suggested by our system or relevant events specified by a user. Inspired by sociology studies, we borrow the knowledge in Proxemics, social force, and social network analysis to model the dynamic relation among social events and the relation among the participants within each event. By analyzing the variation of relation strength among participants and spatiotemporal correlation among events, we discover salient social events in a motion clip and generate an overview video of these events with smooth camera motion using a simulated annealing optimization method. We tested our approach on different motions performed by multiple characters. Our user study shows that our results are preferred in 66.19 percent of the comparisons with those by the camera control approach without event analysis and are comparable (51.79 percent) to professional results by an artist.

  17. Connection between Newtonian simulations and general relativity

    SciTech Connect

    Chisari, Nora Elisa; Zaldarriaga, Matias

    2011-06-15

    On large scales, comparable to the horizon, the observable clustering properties of galaxies are affected by various general relativistic effects. To calculate these effects one needs to consistently solve for the metric, densities, and velocities in a specific coordinate system or gauge. The method of choice for simulating large-scale structure is numerical N-body simulations which are performed in the Newtonian limit. Even though one might worry that the use of the Newtonian approximation would make it impossible to use these simulations to compute properties on very large scales, we show that the simulations are still solving the dynamics correctly even for long modes and we give formulas to obtain the position of particles in the conformal Newtonian gauge given the positions computed in the simulation. We also give formulas to convert from the output coordinates of N-body simulations to the observable coordinates of the particles.

  18. Notification Event Architecture for Traveler Screening: Predictive Traveler Screening Using Event Driven Business Process Management

    ERIC Educational Resources Information Center

    Lynch, John Kenneth

    2013-01-01

    Using an exploratory model of the 9/11 terrorists, this research investigates the linkages between Event Driven Business Process Management (edBPM) and decision making. Although the literature on the role of technology in efficient and effective decision making is extensive, research has yet to quantify the benefit of using edBPM to aid the…

  19. Notification Event Architecture for Traveler Screening: Predictive Traveler Screening Using Event Driven Business Process Management

    ERIC Educational Resources Information Center

    Lynch, John Kenneth

    2013-01-01

    Using an exploratory model of the 9/11 terrorists, this research investigates the linkages between Event Driven Business Process Management (edBPM) and decision making. Although the literature on the role of technology in efficient and effective decision making is extensive, research has yet to quantify the benefit of using edBPM to aid the…

  20. General Relativistic MHD Simulations of Jet Formation

    NASA Technical Reports Server (NTRS)

    Mizuno, Y.; Nishikawa, K.-I.; Hardee, P.; Koide, S.; Fishman, G. J.

    2005-01-01

    We have performed 3-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of jet formation from an accretion disk with/without initial perturbation around a rotating black hole. We input a sinusoidal perturbation (m = 5 mode) in the rotation velocity of the accretion disk. The simulation results show the formation of a relativistic jet from the accretion disk. Although the initial perturbation becomes weakened by the coupling among different modes, it survives and triggers lower modes. As a result, complex non-axisymmetric density structure develops in the disk and the jet. Newtonian MHD simulations of jet formation with a non-axisymmetric mode show the growth of the m = 2 mode but GRMHD simulations cannot see the clear growth of the m = 2 mode.

  1. A general software reliability process simulation technique

    NASA Technical Reports Server (NTRS)

    Tausworthe, Robert C.

    1991-01-01

    The structure and rationale of the generalized software reliability process, together with the design and implementation of a computer program that simulates this process are described. Given assumed parameters of a particular project, the users of this program are able to generate simulated status timelines of work products, numbers of injected anomalies, and the progress of testing, fault isolation, repair, validation, and retest. Such timelines are useful in comparison with actual timeline data, for validating the project input parameters, and for providing data for researchers in reliability prediction modeling.

  2. Spectral Methods in General Relativistic MHD Simulations

    NASA Astrophysics Data System (ADS)

    Garrison, David

    2012-03-01

    In this talk I discuss the use of spectral methods in improving the accuracy of a General Relativistic Magnetohydrodynamic (GRMHD) computer code. I introduce SpecCosmo, a GRMHD code developed as a Cactus arrangement at UHCL, and show simulation results using both Fourier spectral methods and finite differencing. This work demonstrates the use of spectral methods with the FFTW 3.3 Fast Fourier Transform package integrated with the Cactus Framework to perform spectral differencing using MPI.

  3. General simulation algorithm for autocorrelated binary processes

    NASA Astrophysics Data System (ADS)

    Serinaldi, Francesco; Lombardo, Federico

    2017-02-01

    The apparent ubiquity of binary random processes in physics and many other fields has attracted considerable attention from the modeling community. However, generation of binary sequences with prescribed autocorrelation is a challenging task owing to the discrete nature of the marginal distributions, which makes the application of classical spectral techniques problematic. We show that such methods can effectively be used if we focus on the parent continuous process of beta distributed transition probabilities rather than on the target binary process. This change of paradigm results in a simulation procedure effectively embedding a spectrum-based iterative amplitude-adjusted Fourier transform method devised for continuous processes. The proposed algorithm is fully general, requires minimal assumptions, and can easily simulate binary signals with power-law and exponentially decaying autocorrelation functions corresponding, for instance, to Hurst-Kolmogorov and Markov processes. An application to rainfall intermittency shows that the proposed algorithm can also simulate surrogate data preserving the empirical autocorrelation.

  4. Simulation of General Physics laboratory exercise

    NASA Astrophysics Data System (ADS)

    Aceituno, P.; Hernández-Aceituno, J.; Hernández-Cabrera, A.

    2015-01-01

    Laboratory exercises are an important part of general Physics teaching, both during the last years of high school and the first year of college education. Due to the need to acquire enough laboratory equipment for all the students, and the widespread access to computers rooms in teaching, we propose the development of computer simulated laboratory exercises. A representative exercise in general Physics is the calculation of the gravity acceleration value, through the free fall motion of a metal ball. Using a model of the real exercise, we have developed an interactive system which allows students to alter the starting height of the ball to obtain different fall times. The simulation was programmed in ActionScript 3, so that it can be freely executed in any operative system; to ensure the accuracy of the calculations, all the input parameters of the simulations were modelled using digital measurement units, and to allow a statistical management of the resulting data, measurement errors are simulated through limited randomization.

  5. Simulation of MTF experiments at General Fusion

    NASA Astrophysics Data System (ADS)

    Reynolds, Meritt; Froese, Aaron; Barsky, Sandra; Devietien, Peter; Toth, Gabor; Brennan, Dylan; Hooper, Bick

    2016-10-01

    General Fusion (GF) aims to develop a magnetized target fusion (MTF) power plant based on compression of magnetically-confined plasma by liquid metal. GF is testing this compression concept by collapsing solid aluminum liners onto spheromak or tokamak plasmas. To simulate the evolution of the compressing plasma in these experiments, we integrated a moving-mesh method into a finite-volume MHD code (VAC). The single-fluid model includes temperature-dependent resistivity and anisotropic heat transport. The trajectory of the liner is based on experiments and LS-DYNA simulations. During compression the geometry remains axially symmetric, but the MHD simulation is fully 3D to capture ideal and resistive plasma instabilities. We compare simulation to experiment through the primary diagnostic of Mirnov probes embedded in the inner coaxial surface against which the magnetic flux and plasma are compressed by the imploding liner. The MHD simulation reproduces the appearance of n=1 mode activity observed in experiments performed in negative D-shape geometry (MRT and PROSPECTOR machines). The same code predicts more favorable compression in spherical tokamak geometry, having positive D-shape (SPECTOR machine).

  6. Numerical Simulation for Generalized Aurora Computed Tomography

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Aso, T.; Gustavsson, B.; Tanabe, K.; Kadokura, A.; Ogawa, Y.

    2007-12-01

    The conventional method of aurora tomographic inversion is extended to a more generalized aurora computed tomography (CT). The generalized aurora CT is the method to reconstruct energy distribution of auroral precipitating electrons from multimodal data, such as electron density enhancement from the EISCAT radar and cosmic noise absorption (CNA) from imaging riometer, as well as auroral images. In this study, we evaluate the feasibility of the generalized aurora CT by numerical simulation. The forward problem is based on model calculation of auroral emission and electron density enhancement for incident electrons and the mapping of the results to the instruments. Assuming the energy and spatial distributions of the incident electrons, the three-dimensional (3D) distributions of volume emission rate and electron density are calculated. The data observed with the ALIS (Auroral Large Imaging System) cameras, the EISCAT radar, and the imaging riometer are obtained by mapping the volume emission rate and electron density to each instrument. We attempt to retrieve the initial distribution of precipitating electrons from the simulated observational data. The inversion analysis is based on the Bayesian inference, in which the problem is formulated as the maximization problem of posterior probability. The results are compared between the reconstruction from only auroral images and that from multimodal data.

  7. A general formulation for compositional reservoir simulation

    SciTech Connect

    Rodriguez, F.; Guzman, J.; Galindo-Nava, A. |

    1994-12-31

    In this paper the authors present a general formulation to solve the non-linear difference equations that arise in compositional reservoir simulation. The general approach here presented is based on newton`s method and provides a systematic approach to generate several formulations to solve the compositional problem, each possessing a different degree of implicitness and stability characteristics. The Fully-Implicit method is at the higher end of the implicitness spectrum while the IMPECS method, implicit in pressure-explicit in composition and saturation, is at the lower end. They show that all methods may be obtained as particular cases of the fully-implicit method. Regarding the matrix problem, all methods have a similar matrix structure; the composition of the Jacobian matrix is however unique in each case, being in some instances amenable to reductions for optimal solution of the matrix problem. Based on this, a different approach to derive IMPECS type methods is proposed; in this case, the whole set of 2nc + 6 equations, that apply in each gridblock, is reduced to a single pressure equation through matrix reduction operations; this provides a more stable numerical scheme, compared to other published IMPCS methods, in which the subset of thermodynamic equilibrium equations is arbitrarily decoupled form the set of gridblock equations to perform such reduction. The authors discuss how the general formulation here presented can be used to formulate and construct an adaptive-implicit compositional simulators. They also present results on the numerical performance of FI, IMPSEC and IMPECS methods on some test problems.

  8. Event-Driven Control for Networked Control Systems With Quantization and Markov Packet Losses.

    PubMed

    Yang, Hongjiu; Xu, Yang; Zhang, Jinhui

    2016-05-23

    In this paper, event-driven is used in a networked control system (NCS) which is subjected to the effect of quantization and packet losses. A discrete event-detector is used to monitor specific events in the NCS. Both an arbitrary region quantizer and Markov jump packet losses are also considered for the NCS. Based on zoom strategy and Lyapunov theory, a complete proof is given to guarantee mean square stability of the closed-loop system. Stabilization of the NCS is ensured by designing a feedback controller. Lastly, an inverted pendulum model is given to show the advantages and effectiveness of the proposed results.

  9. Modeling the energy performance of event-driven wireless sensor network by using static sink and mobile sink.

    PubMed

    Chen, Jiehui; Salim, Mariam B; Matsumoto, Mitsuji

    2010-01-01

    Wireless Sensor Networks (WSNs) designed for mission-critical applications suffer from limited sensing capacities, particularly fast energy depletion. Regarding this, mobile sinks can be used to balance the energy consumption in WSNs, but the frequent location updates of the mobile sinks can lead to data collisions and rapid energy consumption for some specific sensors. This paper explores an optimal barrier coverage based sensor deployment for event driven WSNs where a dual-sink model was designed to evaluate the energy performance of not only static sensors, but Static Sink (SS) and Mobile Sinks (MSs) simultaneously, based on parameters such as sensor transmission range r and the velocity of the mobile sink v, etc. Moreover, a MS mobility model was developed to enable SS and MSs to effectively collaborate, while achieving spatiotemporal energy performance efficiency by using the knowledge of the cumulative density function (cdf), Poisson process and M/G/1 queue. The simulation results verified that the improved energy performance of the whole network was demonstrated clearly and our eDSA algorithm is more efficient than the static-sink model, reducing energy consumption approximately in half. Moreover, we demonstrate that our results are robust to realistic sensing models and also validate the correctness of our results through extensive simulations.

  10. Modeling the Energy Performance of Event-Driven Wireless Sensor Network by Using Static Sink and Mobile Sink

    PubMed Central

    Chen, Jiehui; Salim, Mariam B.; Matsumoto, Mitsuji

    2010-01-01

    Wireless Sensor Networks (WSNs) designed for mission-critical applications suffer from limited sensing capacities, particularly fast energy depletion. Regarding this, mobile sinks can be used to balance the energy consumption in WSNs, but the frequent location updates of the mobile sinks can lead to data collisions and rapid energy consumption for some specific sensors. This paper explores an optimal barrier coverage based sensor deployment for event driven WSNs where a dual-sink model was designed to evaluate the energy performance of not only static sensors, but Static Sink (SS) and Mobile Sinks (MSs) simultaneously, based on parameters such as sensor transmission range r and the velocity of the mobile sink v, etc. Moreover, a MS mobility model was developed to enable SS and MSs to effectively collaborate, while achieving spatiotemporal energy performance efficiency by using the knowledge of the cumulative density function (cdf), Poisson process and M/G/1 queue. The simulation results verified that the improved energy performance of the whole network was demonstrated clearly and our eDSA algorithm is more efficient than the static-sink model, reducing energy consumption approximately in half. Moreover, we demonstrate that our results are robust to realistic sensing models and also validate the correctness of our results through extensive simulations. PMID:22163503

  11. General relativistic screening in cosmological simulations

    NASA Astrophysics Data System (ADS)

    Hahn, Oliver; Paranjape, Aseem

    2016-10-01

    We revisit the issue of interpreting the results of large volume cosmological simulations in the context of large-scale general relativistic effects. We look for simple modifications to the nonlinear evolution of the gravitational potential ψ that lead on large scales to the correct, fully relativistic description of density perturbations in the Newtonian gauge. We note that the relativistic constraint equation for ψ can be cast as a diffusion equation, with a diffusion length scale determined by the expansion of the Universe. Exploiting the weak time evolution of ψ in all regimes of interest, this equation can be further accurately approximated as a Helmholtz equation, with an effective relativistic "screening" scale ℓ related to the Hubble radius. We demonstrate that it is thus possible to carry out N-body simulations in the Newtonian gauge by replacing Poisson's equation with this Helmholtz equation, involving a trivial change in the Green's function kernel. Our results also motivate a simple, approximate (but very accurate) gauge transformation—δN(k )≈δsim(k )×(k2+ℓ-2)/k2 —to convert the density field δsim of standard collisionless N -body simulations (initialized in the comoving synchronous gauge) into the Newtonian gauge density δN at arbitrary times. A similar conversion can also be written in terms of particle positions. Our results can be interpreted in terms of a Jeans stability criterion induced by the expansion of the Universe. The appearance of the screening scale ℓ in the evolution of ψ , in particular, leads to a natural resolution of the "Jeans swindle" in the presence of superhorizon modes.

  12. Event-driven charge-coupled device design and applications therefor

    NASA Technical Reports Server (NTRS)

    Doty, John P. (Inventor); Ricker, Jr., George R. (Inventor); Burke, Barry E. (Inventor); Prigozhin, Gregory Y. (Inventor)

    2005-01-01

    An event-driven X-ray CCD imager device uses a floating-gate amplifier or other non-destructive readout device to non-destructively sense a charge level in a charge packet associated with a pixel. The output of the floating-gate amplifier is used to identify each pixel that has a charge level above a predetermined threshold. If the charge level is above a predetermined threshold the charge in the triggering charge packet and in the charge packets from neighboring pixels need to be measured accurately. A charge delay register is included in the event-driven X-ray CCD imager device to enable recovery of the charge packets from neighboring pixels for accurate measurement. When a charge packet reaches the end of the charge delay register, control logic either dumps the charge packet, or steers the charge packet to a charge FIFO to preserve it if the charge packet is determined to be a packet that needs accurate measurement. A floating-diffusion amplifier or other low-noise output stage device, which converts charge level to a voltage level with high precision, provides final measurement of the charge packets. The voltage level is eventually digitized by a high linearity ADC.

  13. EVENT DRIVEN AUTOMATIC STATE MODIFICATION OF BNL'S BOOSTER FOR NASA SPACE RADIATION LABORATORY SOLAR PARTICLE SIMULATOR.

    SciTech Connect

    BROWN, D.; BINELLO, S.; HARVEY, M.; MORRIS, J.; RUSEK, A.; TSOUPAS, N.

    2005-05-16

    The NASA Space Radiation Laboratory (NSRL) was constructed in collaboration with NASA for the purpose of performing radiation effect studies for the NASA space program. The NSRL makes use of heavy ions in the range of 0.05 to 3 GeV/n slow extracted from BNL's AGS Booster. NASA is interested in reproducing the energy spectrum from a solar flare in the space environment for a single ion species. To do this we have built and tested a set of software tools which allow the state of the Booster and the NSRL beam line to be changed automatically. In this report we will describe the system and present results of beam tests.

  14. Event-Driven Simulation and Analysis of an Underwater Acoustic Local Area Network

    DTIC Science & Technology

    2010-06-01

    Reliability.....................................................................................5 a. Convolutional Coding...rate Convolutional Coding Multipath Guard Period Average Transmit Power 20 watts at power level 08 (max) @ 21 VDC Source Level: 183 dB re: 1 µPa...reliability of the transmission. These methods involve the use of convolutional coding, multipath guard periods, and data redundancy. However, these

  15. Event-driven visual attention for the humanoid robot iCub

    PubMed Central

    Rea, Francesco; Metta, Giorgio; Bartolozzi, Chiara

    2013-01-01

    Fast reaction to sudden and potentially interesting stimuli is a crucial feature for safe and reliable interaction with the environment. Here we present a biologically inspired attention system developed for the humanoid robot iCub. It is based on input from unconventional event-driven vision sensors and an efficient computational method. The resulting system shows low-latency and fast determination of the location of the focus of attention. The performance is benchmarked against an instance of the state of the art in robotics artificial attention system used in robotics. Results show that the proposed system is two orders of magnitude faster that the benchmark in selecting a new stimulus to attend. PMID:24379753

  16. Design of an Event-Driven Random-Access-Windowing CCD-Based Camera

    NASA Technical Reports Server (NTRS)

    Monacos, Steve P.; Lam, Raymond K.; Portillo, Angel A.; Ortiz, Gerardo G.

    2003-01-01

    Commercially available cameras are not design for the combination of single frame and high-speed streaming digital video with real-time control of size and location of multiple regions-of-interest (ROI). A new control paradigm is defined to eliminate the tight coupling between the camera logic and the host controller. This functionality is achieved by defining the indivisible pixel read out operation on a per ROI basis with in-camera time keeping capability. This methodology provides a Random Access, Real-Time, Event-driven (RARE) camera for adaptive camera control and is will suited for target tracking applications requiring autonomous control of multiple ROI's. This methodology additionally provides for reduced ROI read out time and higher frame rates compared to the original architecture by avoiding external control intervention during the ROI read out process.

  17. Active on-demand service method based on event-driven architecture for geospatial data retrieval

    NASA Astrophysics Data System (ADS)

    Fan, Minghu; Fan, Hong; Chen, Nengcheng; Chen, Zeqiang; Du, Wu

    2013-07-01

    Timely on-demand access to geospatial data is necessary for environmental observation and disaster response. However, traditional service methods for acquiring geospatial data are inefficient and cumbersome, which is not beneficial for timely data acquisition. In these service methods, data are obtained and published by managers and are then left to users to discover and to retrieve them. To solve this problem, we propose an event-driven active on-demand data service method, for which a prototype based on sensor web technologies is demonstrated. First, we select a subset of observed properties as the attributes of an observation event of a data service system. Event-filtering technologies are then employed to find the data desired by users. Finally, the data that meet the subscription requirement are pushed to subscribers on time. The aims of the implementation of the method are to test the suitability of the observation and measurement (O&M) profile for Earth observation and OGC event pattern markup language (EML) specification. We determined the attributes of observation events according to the requirement of the data service and encoded observation event information using the OGC Observations and Measurements specification. We encoded the information under filtering conditions using the OGC Event Pattern Markup Language specification. We implemented a data service method that is based on event-driven architecture via a combination of some sensor web enablement services. Finally, we verified the feasibility of the method using MODIS data from the forest fires that occurred on February 7, 2009, in Victoria, Australia. The results show that the proposed method can achieve actively pushing the desired data to subscribers in the shortest possible time. O&M profiles for Earth observation and EML are suitable for the metadata encoding of observation events and the encoding of subscription information respectively. They match well for the data service in the system.

  18. Generalized Maintenance Trainer Simulator: User Manual.

    DTIC Science & Technology

    1982-03-01

    be created in segments , each having up to 1800 images. Creation of the data base that controls the simulation is accomplished at the instructor...individual systems and from one target system to another. Since it also must present the simulated system in its normal operating condition, exercises can...For example, consider an equipment that operates in 20 frequency bands divided into two banks of 10 bands each, in which the two banks are identical in

  19. WE-G-BRA-02: SafetyNet: Automating Radiotherapy QA with An Event Driven Framework

    SciTech Connect

    Hadley, S; Kessler, M; Litzenberg, D; Lee, C; Irrer, J; Chen, X; Acosta, E; Weyburne, G; Lam, K; Younge, K; Matuszak, M; Keranen, W; Covington, E; Moran, J

    2015-06-15

    Purpose: Quality assurance is an essential task in radiotherapy that often requires many manual tasks. We investigate the use of an event driven framework in conjunction with software agents to automate QA and eliminate wait times. Methods: An in house developed subscription-publication service, EventNet, was added to the Aria OIS to be a message broker for critical events occurring in the OIS and software agents. Software agents operate without user intervention and perform critical QA steps. The results of the QA are documented and the resulting event is generated and passed back to EventNet. Users can subscribe to those events and receive messages based on custom filters designed to send passing or failing results to physicists or dosimetrists. Agents were developed to expedite the following QA tasks: Plan Revision, Plan 2nd Check, SRS Winston-Lutz isocenter, Treatment History Audit, Treatment Machine Configuration. Results: Plan approval in the Aria OIS was used as the event trigger for plan revision QA and Plan 2nd check agents. The agents pulled the plan data, executed the prescribed QA, stored the results and updated EventNet for publication. The Winston Lutz agent reduced QA time from 20 minutes to 4 minutes and provided a more accurate quantitative estimate of radiation isocenter. The Treatment Machine Configuration agent automatically reports any changes to the Treatment machine or HDR unit configuration. The agents are reliable, act immediately, and execute each task identically every time. Conclusion: An event driven framework has inverted the data chase in our radiotherapy QA process. Rather than have dosimetrists and physicists push data to QA software and pull results back into the OIS, the software agents perform these steps immediately upon receiving the sentinel events from EventNet. Mr Keranen is an employee of Varian Medical Systems. Dr. Moran’s institution receives research support for her effort for a linear accelerator QA project from

  20. Innovation of IT metasystems by means of event-driven paradigm using QDMS

    NASA Astrophysics Data System (ADS)

    Nedic, Vladimir; Despotovic, Danijela; Cvetanovic, Slobodan; Despotovic, Milan; Eric, Milan

    2016-10-01

    Globalisation of world economy brings new and more complex demands to business systems. In order to respond to these trends, business systems apply new paradigms that are inevitable reflecting on management metasystems - quality assurance (QA), as well as on information technology (IT) metasystems. Small and medium enterprises (in particular in food industry) do not have possibilities to access external resources to the extent that could provide adequate keeping up with these trends. That raises the question how to enhance synergetic effect of interaction between existing QA and IT metasystems in order to overcome resource gap and achieve set goals by internal resources. The focus of this article is to propose a methodology for utilisation of potential of quality assurance document management system (QDMS) as prototypical platform for initiating, developing, testing and improving new functionalities that are required by IT as support for buiness system management. In that way QDMS plays a role of catalyst that not only accelerates but could also enhance selectivity of the reactions of QA and IT metasystems and direct them on finding new functionalities based on event-driven paradigm. The article tries to show the process of modelling, development and implementation of a possible approach to this problem through conceptual survey and practical solution in the food industry.

  1. FusionAnalyser: a new graphical, event-driven tool for fusion rearrangements discovery

    PubMed Central

    Piazza, Rocco; Pirola, Alessandra; Spinelli, Roberta; Valletta, Simona; Redaelli, Sara; Magistroni, Vera; Gambacorti-Passerini, Carlo

    2012-01-01

    Gene fusions are common driver events in leukaemias and solid tumours; here we present FusionAnalyser, a tool dedicated to the identification of driver fusion rearrangements in human cancer through the analysis of paired-end high-throughput transcriptome sequencing data. We initially tested FusionAnalyser by using a set of in silico randomly generated sequencing data from 20 known human translocations occurring in cancer and subsequently using transcriptome data from three chronic and three acute myeloid leukaemia samples. in all the cases our tool was invariably able to detect the presence of the correct driver fusion event(s) with high specificity. In one of the acute myeloid leukaemia samples, FusionAnalyser identified a novel, cryptic, in-frame ETS2–ERG fusion. A fully event-driven graphical interface and a flexible filtering system allow complex analyses to be run in the absence of any a priori programming or scripting knowledge. Therefore, we propose FusionAnalyser as an efficient and robust graphical tool for the identification of functional rearrangements in the context of high-throughput transcriptome sequencing data. PMID:22570408

  2. Heart rate regulation during cycle-ergometer exercise via event-driven biofeedback.

    PubMed

    Argha, Ahmadreza; Su, Steven W; Celler, Branko G

    2017-03-01

    This paper is devoted to the problem of regulating the heart rate response along a predetermined reference profile, for cycle-ergometer exercises designed for training or cardio-respiratory rehabilitation. The controller designed in this study is a non-conventional, non-model-based, proportional, integral and derivative (PID) controller. The PID controller commands can be transmitted as biofeedback auditory commands, which can be heard and interpreted by the exercising subject to increase or reduce exercise intensity. However, in such a case, for the purposes of effectively communicating to the exercising subject a change in the required exercise intensity, the timing of this feedback signal relative to the position of the pedals becomes critical. A feedback signal delivered when the pedals are not in a suitable position to efficiently exert force may be ineffective and this may, in turn, lead to the cognitive disengagement of the user from the feedback controller. This note examines a novel form of control system which has been expressly designed for this project. The system is called an "actuator-based event-driven control system". The proposed control system was experimentally verified using 24 healthy male subjects who were randomly divided into two separate groups, along with cross-validation scheme. A statistical analysis was employed to test the generalisation of the PID tunes, derived based on the average transfer functions of the two groups, and it revealed that there were no significant differences between the mean values of root mean square of the tracking error of two groups (3.9 vs. 3.7 bpm, [Formula: see text]). Furthermore, the results of a second statistical hypothesis test showed that the proposed PID controller with novel synchronised biofeedback mechanism has better performance compared to a conventional PID controller with a fixed-rate biofeedback mechanism (Group 1: 3.9 vs. 5.0 bpm, Group 2: 3.7 vs. 4.4 bpm, [Formula: see text]).

  3. Real-time gesture interface based on event-driven processing from stereo silicon retinas.

    PubMed

    Lee, Jun Haeng; Delbruck, Tobi; Pfeiffer, Michael; Park, Paul K J; Shin, Chang-Woo; Ryu, Hyunsurk Eric; Kang, Byung Chang

    2014-12-01

    We propose a real-time hand gesture interface based on combining a stereo pair of biologically inspired event-based dynamic vision sensor (DVS) silicon retinas with neuromorphic event-driven postprocessing. Compared with conventional vision or 3-D sensors, the use of DVSs, which output asynchronous and sparse events in response to motion, eliminates the need to extract movements from sequences of video frames, and allows significantly faster and more energy-efficient processing. In addition, the rate of input events depends on the observed movements, and thus provides an additional cue for solving the gesture spotting problem, i.e., finding the onsets and offsets of gestures. We propose a postprocessing framework based on spiking neural networks that can process the events received from the DVSs in real time, and provides an architecture for future implementation in neuromorphic hardware devices. The motion trajectories of moving hands are detected by spatiotemporally correlating the stereoscopically verged asynchronous events from the DVSs by using leaky integrate-and-fire (LIF) neurons. Adaptive thresholds of the LIF neurons achieve the segmentation of trajectories, which are then translated into discrete and finite feature vectors. The feature vectors are classified with hidden Markov models, using a separate Gaussian mixture model for spotting irrelevant transition gestures. The disparity information from stereovision is used to adapt LIF neuron parameters to achieve recognition invariant of the distance of the user to the sensor, and also helps to filter out movements in the background of the user. Exploiting the high dynamic range of DVSs, furthermore, allows gesture recognition over a 60-dB range of scene illuminance. The system achieves recognition rates well over 90% under a variety of variable conditions with static and dynamic backgrounds with naïve users.

  4. Event-driven time-optimal control for a class of discontinuous bioreactors.

    PubMed

    Moreno, Jaime A; Betancur, Manuel J; Buitrón, Germán; Moreno-Andrade, Iván

    2006-07-05

    Discontinuous bioreactors may be further optimized for processing inhibitory substrates using a convenient fed-batch mode. To do so the filling rate must be controlled in such a way as to push the reaction rate to its maximum value, by increasing the substrate concentration just up to the point where inhibition begins. However, an exact optimal controller requires measuring several variables (e.g., substrate concentrations in the feed and in the tank) and also good model knowledge (e.g., yield and kinetic parameters), requirements rarely satisfied in real applications. An environmentally important case, that exemplifies all these handicaps, is toxicant wastewater treatment. There the lack of online practical pollutant sensors may allow unforeseen high shock loads to be fed to the bioreactor, causing biomass inhibition that slows down the treatment process and, in extreme cases, even renders the biological process useless. In this work an event-driven time-optimal control (ED-TOC) is proposed to circumvent these limitations. We show how to detect a "there is inhibition" event by using some computable function of the available measurements. This event drives the ED-TOC to stop the filling. Later, by detecting the symmetric event, "there is no inhibition," the ED-TOC may restart the filling. A fill-react cycling then maintains the process safely hovering near its maximum reaction rate, allowing a robust and practically time-optimal operation of the bioreactor. An experimental study case of a wastewater treatment process application is presented. There the dissolved oxygen concentration was used to detect the events needed to drive the controller.

  5. General Aviation Cockpit Weather Information System Simulation Studies

    NASA Technical Reports Server (NTRS)

    McAdaragh, Ray; Novacek, Paul

    2003-01-01

    This viewgraph presentation provides information on two experiments on the effectiveness of a cockpit weather information system on a simulated general aviation flight. The presentation covers the simulation hardware configuration, the display device screen layout, a mission scenario, conclusions, and recommendations. The second experiment, with its own scenario and conclusions, is a follow-on experiment.

  6. Test and evaluation of the generalized gate logic system simulator

    NASA Technical Reports Server (NTRS)

    Miner, Paul S.

    1991-01-01

    The results of the initial testing of the Generalized Gate Level Logic Simulator (GGLOSS) are discussed. The simulator is a special purpose fault simulator designed to assist in the analysis of the effects of random hardware failures on fault tolerant digital computer systems. The testing of the simulator covers two main areas. First, the simulation results are compared with data obtained by monitoring the behavior of hardware. The circuit used for these comparisons is an incomplete microprocessor design based upon the MIL-STD-1750A Instruction Set Architecture. In the second area of testing, current simulation results are compared with experimental data obtained using precursors of the current tool. In each case, a portion of the earlier experiment is confirmed. The new results are then viewed from a different perspective in order to evaluate the usefulness of this simulation strategy.

  7. Toward unified hybrid simulation techniques for spiking neural networks.

    PubMed

    D'Haene, Michiel; Hermans, Michiel; Schrauwen, Benjamin

    2014-06-01

    In the field of neural network simulation techniques, the common conception is that spiking neural network simulators can be divided in two categories: time-step-based and event-driven methods. In this letter, we look at state-of-the art simulation techniques in both categories and show that a clear distinction between both methods is increasingly difficult to define. In an attempt to improve the weak points of each simulation method, ideas of the alternative method are, sometimes unknowingly, incorporated in the simulation engine. Clearly the ideal simulation method is a mix of both methods. We formulate the key properties of such an efficient and generally applicable hybrid approach.

  8. Predicting analysis time in event-driven clinical trials with event-reporting lag.

    PubMed

    Wang, Jianming; Ke, Chunlei; Jiang, Qi; Zhang, Charlie; Snapinn, Steven

    2012-04-30

    For a clinical trial with a time-to-event primary endpoint, the rate of accrual of the event of interest determines the timing of the analysis, upon which significant resources and strategic planning depend. It is important to be able to predict the analysis time early and accurately. Currently available methods use either parametric or nonparametric models to predict the analysis time based on accumulating information about enrollment, event, and study withdrawal rates and implicitly assume that the available data are completely reported at the time of performing the prediction. This assumption, however, may not be true when it takes a certain amount of time (i.e., event-reporting lag) for an event to be reported, in which case, the data are incomplete for prediction. Ignoring the event-reporting lag could substantially impact the accuracy of the prediction. In this paper, we describe a general parametric model to incorporate event-reporting lag into analysis time prediction. We develop a prediction procedure using a Bayesian method and provide detailed implementations for exponential distributions. Some simulations were performed to evaluate the performance of the proposed method. An application to an on-going clinical trial is also described. Copyright © 2012 John Wiley & Sons, Ltd.

  9. A Comparison of General Case In Vivo and General Case Simulation Plus In Vivo Training.

    ERIC Educational Resources Information Center

    McDonnell, John J.; Ferguson, Brad

    1988-01-01

    The study examined the relative effectiveness and efficiency of general case in vivo and general case simulation plus in vivo training in teaching six students with moderate and severe disabilities to purchase items in fast-food restaurants. Although both strategies led to reliable performance in nontrained settings, the in vivo instruction…

  10. Sampling of general correlators in worm-algorithm based simulations

    NASA Astrophysics Data System (ADS)

    Rindlisbacher, Tobias; Åkerlund, Oscar; de Forcrand, Philippe

    2016-08-01

    Using the complex ϕ4-model as a prototype for a system which is simulated by a worm algorithm, we show that not only the charged correlator <ϕ* (x) ϕ (y) >, but also more general correlators such as < | ϕ (x) | | ϕ (y) | > or < arg ⁡ (ϕ (x)) arg ⁡ (ϕ (y)) >, as well as condensates like < | ϕ | >, can be measured at every step of the Monte Carlo evolution of the worm instead of on closed-worm configurations only. The method generalizes straightforwardly to other systems simulated by worms, such as spin or sigma models.

  11. The development of an interim generalized gate logic software simulator

    NASA Technical Reports Server (NTRS)

    Mcgough, J. G.; Nemeroff, S.

    1985-01-01

    A proof-of-concept computer program called IGGLOSS (Interim Generalized Gate Logic Software Simulator) was developed and is discussed. The simulator engine was designed to perform stochastic estimation of self test coverage (fault-detection latency times) of digital computers or systems. A major attribute of the IGGLOSS is its high-speed simulation: 9.5 x 1,000,000 gates/cpu sec for nonfaulted circuits and 4.4 x 1,000,000 gates/cpu sec for faulted circuits on a VAX 11/780 host computer.

  12. Generalized dynamic engine simulation techniques for the digital computer

    NASA Technical Reports Server (NTRS)

    Sellers, J.; Teren, F.

    1974-01-01

    Recently advanced simulation techniques have been developed for the digital computer and used as the basis for development of a generalized dynamic engine simulation computer program, called DYNGEN. This computer program can analyze the steady state and dynamic performance of many kinds of aircraft gas turbine engines. Without changes to the basic program DYNGEN can analyze one- or two-spool turbofan engines. The user must supply appropriate component performance maps and design-point information. Examples are presented to illustrate the capabilities of DYNGEN in the steady state and dynamic modes of operation. The analytical techniques used in DYNGEN are briefly discussed, and its accuracy is compared with a comparable simulation using the hybrid computer. The impact of DYNGEN and similar all-digital programs on future engine simulation philosophy is also discussed.

  13. Generalized dynamic engine simulation techniques for the digital computer

    NASA Technical Reports Server (NTRS)

    Sellers, J.; Teren, F.

    1974-01-01

    Recently advanced simulation techniques have been developed for the digital computer and used as the basis for development of a generalized dynamic engine simulation computer program, called DYNGEN. This computer program can analyze the steady state and dynamic performance of many kinds of aircraft gas turbine engines. Without changes to the basic program, DYNGEN can analyze one- or two-spool turbofan engines. The user must supply appropriate component performance maps and design-point information. Examples are presented to illustrate the capabilities of DYNGEN in the steady state and dynamic modes of operation. The analytical techniques used in DYNGEN are briefly discussed, and its accuracy is compared with a comparable simulation using the hybrid computer. The impact of DYNGEN and similar all-digital programs on future engine simulation philosophy is also discussed.

  14. Generalized dynamic engine simulation techniques for the digital computers

    NASA Technical Reports Server (NTRS)

    Sellers, J.; Teren, F.

    1975-01-01

    Recently advanced simulation techniques have been developed for the digital computer and used as the basis for development of a generalized dynamic engine simulation computer program, called DYNGEN. This computer program can analyze the steady state and dynamic performance of many kinds of aircraft gas turbine engines. Without changes to the basic program, DYNGEN can analyze one- or two-spool turbofan engines. The user must supply appropriate component performance maps and design point information. Examples are presented to illustrate the capabilities of DYNGEN in the steady state and dynamic modes of operation. The analytical techniques used in DYNGEN are briefly discussed, and its accuracy is compared with a comparable simulation using the hybrid computer. The impact of DYNGEN and similar digital programs on future engine simulation philosophy is also discussed.

  15. Optimal Weights in Serial Generalized-Ensemble Simulations.

    PubMed

    Chelli, Riccardo

    2010-07-13

    In serial generalized-ensemble simulations, the sampling of a collective coordinate of a system is enhanced through non-Boltzmann weighting schemes. A popular version of such methods is certainly the simulated tempering technique, which is based on a random walk in temperature ensembles to explore the phase space more thoroughly. The most critical aspect of serial generalized-ensemble methods with respect to their parallel counterparts, such as replica exchange, is the difficulty of weight determination. Here we propose an adaptive approach to update the weights on the fly during the simulation. The algorithm is based on generalized forms of the Bennett acceptance ratio and of the free energy perturbation. It does not require intensive communication between processors and, therefore, is prone to be used in distributed computing environments with modest computational cost. We illustrate the method in a series of molecular dynamics simulations of a model system and compare its performances to two recent approaches, one based on adaptive Bayesian-weighted histogram analysis and the other based on initial estimates of weight factors obtained by potential energy averages.

  16. The power of event-driven analytics in Large Scale Data Processing

    SciTech Connect

    2011-02-24

    FeedZai is a software company specialized in creating high-­-throughput low-­-latency data processing solutions. FeedZai develops a product called "FeedZai Pulse" for continuous event-­-driven analytics that makes application development easier for end users. It automatically calculates key performance indicators and baselines, showing how current performance differ from previous history, creating timely business intelligence updated to the second. The tool does predictive analytics and trend analysis, displaying data on real-­-time web-­-based graphics. In 2010 FeedZai won the European EBN Smart Entrepreneurship Competition, in the Digital Models category, being considered one of the "top-­-20 smart companies in Europe". The main objective of this seminar/workshop is to explore the topic for large-­-scale data processing using Complex Event Processing and, in particular, the possible uses of Pulse in the scope of the data processing needs of CERN. Pulse is available as open-­-source and can be licensed both for non-­-commercial and commercial applications. FeedZai is interested in exploring possible synergies with CERN in high-­-volume low-­-latency data processing applications. The seminar will be structured in two sessions, the first one being aimed to expose the general scope of FeedZai's activities, and the second focused on Pulse itself: 10:00-11:00 FeedZai and Large Scale Data Processing Introduction to FeedZai FeedZai Pulse and Complex Event Processing Demonstration Use-Cases and Applications Conclusion and Q&A 11:00-11:15 Coffee break 11:15-12:30 FeedZai Pulse Under the Hood A First FeedZai Pulse Application PulseQL overview Defining KPIs and Baselines Conclusion and Q&A About the speakers Nuno Sebastião is the CEO of FeedZai. Having worked for many years for the European Space Agency (ESA), he was responsible the overall design and development of Satellite Simulation Infrastructure of the agency. Having left ESA to found FeedZai, Nuno is

  17. The power of event-driven analytics in Large Scale Data Processing

    ScienceCinema

    None

    2016-07-12

    FeedZai is a software company specialized in creating high-­-throughput low-­-latency data processing solutions. FeedZai develops a product called "FeedZai Pulse" for continuous event-­-driven analytics that makes application development easier for end users. It automatically calculates key performance indicators and baselines, showing how current performance differ from previous history, creating timely business intelligence updated to the second. The tool does predictive analytics and trend analysis, displaying data on real-­-time web-­-based graphics. In 2010 FeedZai won the European EBN Smart Entrepreneurship Competition, in the Digital Models category, being considered one of the "top-­-20 smart companies in Europe". The main objective of this seminar/workshop is to explore the topic for large-­-scale data processing using Complex Event Processing and, in particular, the possible uses of Pulse in the scope of the data processing needs of CERN. Pulse is available as open-­-source and can be licensed both for non-­-commercial and commercial applications. FeedZai is interested in exploring possible synergies with CERN in high-­-volume low-­-latency data processing applications. The seminar will be structured in two sessions, the first one being aimed to expose the general scope of FeedZai's activities, and the second focused on Pulse itself: 10:00-11:00 FeedZai and Large Scale Data Processing Introduction to FeedZai FeedZai Pulse and Complex Event Processing Demonstration Use-Cases and Applications Conclusion and Q&A 11:00-11:15 Coffee break 11:15-12:30 FeedZai Pulse Under the Hood A First FeedZai Pulse Application PulseQL overview Defining KPIs and Baselines Conclusion and Q&A About the speakers Nuno Sebastião is the CEO of FeedZai. Having worked for many years for the European Space Agency (ESA), he was responsible the overall design and development of Satellite Simulation Infrastructure of the agency. Having left ESA to found FeedZai, Nuno is

  18. The architecture of Newton, a general-purpose dynamics simulator

    NASA Technical Reports Server (NTRS)

    Cremer, James F.; Stewart, A. James

    1989-01-01

    The architecture for Newton, a general-purpose system for simulating the dynamics of complex physical objects, is described. The system automatically formulates and analyzes equations of motion, and performs automatic modification of this system equations when necessitated by changes in kinematic relationships between objects. Impact and temporary contact are handled, although only using simple models. User-directed influence of simulations is achieved using Newton's module, which can be used to experiment with the control of many-degree-of-freedom articulated objects.

  19. The architecture of Newton, a general-purpose dynamics simulator

    NASA Technical Reports Server (NTRS)

    Cremer, James F.; Stewart, A. James

    1989-01-01

    The architecture for Newton, a general-purpose system for simulating the dynamics of complex physical objects, is described. The system automatically formulates and analyzes equations of motion, and performs automatic modification of this system equations when necessitated by changes in kinematic relationships between objects. Impact and temporary contact are handled, although only using simple models. User-directed influence of simulations is achieved using Newton's module, which can be used to experiment with the control of many-degree-of-freedom articulated objects.

  20. Generalized Fluid System Simulation Program (GFSSP) Version 6 - General Purpose Thermo-Fluid Network Analysis Software

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok; Leclair, Andre; Moore, Ric; Schallhorn, Paul

    2011-01-01

    GFSSP stands for Generalized Fluid System Simulation Program. It is a general-purpose computer program to compute pressure, temperature and flow distribution in a flow network. GFSSP calculates pressure, temperature, and concentrations at nodes and calculates flow rates through branches. It was primarily developed to analyze Internal Flow Analysis of a Turbopump Transient Flow Analysis of a Propulsion System. GFSSP development started in 1994 with an objective to provide a generalized and easy to use flow analysis tool for thermo-fluid systems.

  1. Simulation Output Analysis for General State Space Markov Chains.

    DTIC Science & Technology

    1981-02-01

    based on just one simulation run. These methods for constructing confidence intervals are all based on central limit theorems for the underlying...considerations which limit its application. However, the method can be used to increase the rate of regeneration points when using the standard regenerative...aperiodic (this will generally be the case for GSMP’s), functions of Vk will enjoy a central limit theorem with a variance constant of the form 00 (4.1) a 2

  2. The Architecture of Newton, a General-Purpose Dynamics Simulator

    DTIC Science & Technology

    1989-01-01

    11 N The Architecture of Newton, a General-Purpose Dynamics 0 Simulator OTIC James F. Cremer ELECTE A. James Stewart JUL 141989f l Computer Science...173SS, ONR grant N00t4.SK-0281 and DARPA grant N0014-OOK.0S91 Support for James Stewart is provided in part by U.S. Army Math-4.3 Control matica Sciences

  3. Reducing usage of the computational resources by event driven approach to model predictive control

    NASA Astrophysics Data System (ADS)

    Misik, Stefan; Bradac, Zdenek; Cela, Arben

    2017-08-01

    This paper deals with a real-time and optimal control of dynamic systems while also considers the constraints which these systems might be subject to. Main objective of this work is to propose a simple modification of the existing Model Predictive Control approach to better suit needs of computational resource-constrained real-time systems. An example using model of a mechanical system is presented and the performance of the proposed method is evaluated in a simulated environment.

  4. Do Downscaled General Circulation Models Reliably Simulate Current Climatic Conditions?

    NASA Astrophysics Data System (ADS)

    Hay, L.; Bock, A. R.; McCabe, G. J., Jr.; Markstrom, S. L.; Atkinson, D.

    2016-12-01

    The accuracy of statistically-downscaled (SD) General Circulation Model (GCM) simulations of monthly surface climate for historical conditions (1950-2000) used to drive a monthly water balance model (MWBM) were assessed for the conterminous United States (CONUS). SD monthly precipitation (PPT) and atmospheric temperature (TAVE) from 95 GCMs (38 from the coupled model intercomparison project (CMIP) 3 and 57 from CMIP5) were used as inputs to a MWBM. Input (PPT, TAVE) and output (snow water equivalent (SWE), and runoff (RUN)) MWBM variables were evaluated by comparing variables computed using historical climate forcings (developed from gridded station data (GSD)) with those computed using historical SD climate. Distributions of GSD- and SD-based MWBM variables were compared using the two-sample Kolmogorov-Smirnov test (KS Test). When all MWBM variables were considered, the KS Test results showed an overall improvement by the CMIP5- relative to CMIP3-based simulations, likely due to improvements in PPT simulations. Results from this study indicate that for the majority of the CONUS, there are downscaled GCMs that can reliably simulate current climatic conditions. But, in some locations (particularly in California), there are no downscaled GCMs tested that replicate historical conditions for all four MWBM variables. In these locations, improved GCM simulations of precipitation are needed to more reliably estimate components of the hydrologic cycle.

  5. A High-Speed, Event-Driven, Active Pixel Sensor Readout for Photon-Counting Microchannel Plate Detectors

    NASA Technical Reports Server (NTRS)

    Kimble, Randy A.; Pain, Bedabrata; Norton, Timothy J.; Haas, J. Patrick; Oegerle, William R. (Technical Monitor)

    2002-01-01

    Silicon array readouts for microchannel plate intensifiers offer several attractive features. In this class of detector, the electron cloud output of the MCP intensifier is converted to visible light by a phosphor; that light is then fiber-optically coupled to the silicon array. In photon-counting mode, the resulting light splashes on the silicon array are recognized and centroided to fractional pixel accuracy by off-chip electronics. This process can result in very high (MCP-limited) spatial resolution while operating at a modest MCP gain (desirable for dynamic range and long term stability). The principal limitation of intensified CCD systems of this type is their severely limited local dynamic range, as accurate photon counting is achieved only if there are not overlapping event splashes within the frame time of the device. This problem can be ameliorated somewhat by processing events only in pre-selected windows of interest of by using an addressable charge injection device (CID) for the readout array. We are currently pursuing the development of an intriguing alternative readout concept based on using an event-driven CMOS Active Pixel Sensor. APS technology permits the incorporation of discriminator circuitry within each pixel. When coupled with suitable CMOS logic outside the array area, the discriminator circuitry can be used to trigger the readout of small sub-array windows only when and where an event splash has been detected, completely eliminating the local dynamic range problem, while achieving a high global count rate capability and maintaining high spatial resolution. We elaborate on this concept and present our progress toward implementing an event-driven APS readout.

  6. A High-Speed, Event-Driven, Active Pixel Sensor Readout for Photon-Counting Microchannel Plate Detectors

    NASA Technical Reports Server (NTRS)

    Kimble, Randy A.; Pain, B.; Norton, T. J.; Haas, P.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Silicon array readouts for microchannel plate intensifiers offer several attractive features. In this class of detector, the electron cloud output of the MCP intensifier is converted to visible light by a phosphor; that light is then fiber-optically coupled to the silicon array. In photon-counting mode, the resulting light splashes on the silicon array are recognized and centroided to fractional pixel accuracy by off-chip electronics. This process can result in very high (MCP-limited) spatial resolution for the readout while operating at a modest MCP gain (desirable for dynamic range and long term stability). The principal limitation of intensified CCD systems of this type is their severely limited local dynamic range, as accurate photon counting is achieved only if there are not overlapping event splashes within the frame time of the device. This problem can be ameliorated somewhat by processing events only in pre-selected windows of interest or by using an addressable charge injection device (CID) for the readout array. We are currently pursuing the development of an intriguing alternative readout concept based on using an event-driven CMOS Active Pixel Sensor. APS technology permits the incorporation of discriminator circuitry within each pixel. When coupled with suitable CMOS logic outside the array area, the discriminator circuitry can be used to trigger the readout of small sub-array windows only when and where an event splash has been detected, completely eliminating the local dynamic range problem, while achieving a high global count rate capability and maintaining high spatial resolution. We elaborate on this concept and present our progress toward implementing an event-driven APS readout.

  7. Accurate Event-Driven Motion Compensation in High-Resolution PET Incorporating Scattered and Random Events

    PubMed Central

    Dinelle, Katie; Cheng, Ju-Chieh; Shilov, Mikhail A.; Segars, William P.; Lidstone, Sarah C.; Blinder, Stephan; Rousset, Olivier G.; Vajihollahi, Hamid; Tsui, Benjamin M. W.; Wong, Dean F.; Sossi, Vesna

    2010-01-01

    With continuing improvements in spatial resolution of positron emission tomography (PET) scanners, small patient movements during PET imaging become a significant source of resolution degradation. This work develops and investigates a comprehensive formalism for accurate motion-compensated reconstruction which at the same time is very feasible in the context of high-resolution PET. In particular, this paper proposes an effective method to incorporate presence of scattered and random coincidences in the context of motion (which is similarly applicable to various other motion correction schemes). The overall reconstruction framework takes into consideration missing projection data which are not detected due to motion, and additionally, incorporates information from all detected events, including those which fall outside the field-of-view following motion correction. The proposed approach has been extensively validated using phantom experiments as well as realistic simulations of a new mathematical brain phantom developed in this work, and the results for a dynamic patient study are also presented. PMID:18672420

  8. Automatic CT simulation optimization for radiation therapy: A general strategy

    SciTech Connect

    Li, Hua Chen, Hsin-Chen; Tan, Jun; Gay, Hiram; Michalski, Jeff M.; Mutic, Sasa; Yu, Lifeng; Anastasio, Mark A.; Low, Daniel A.

    2014-03-15

    Purpose: In radiation therapy, x-ray computed tomography (CT) simulation protocol specifications should be driven by the treatment planning requirements in lieu of duplicating diagnostic CT screening protocols. The purpose of this study was to develop a general strategy that allows for automatically, prospectively, and objectively determining the optimal patient-specific CT simulation protocols based on radiation-therapy goals, namely, maintenance of contouring quality and integrity while minimizing patient CT simulation dose. Methods: The authors proposed a general prediction strategy that provides automatic optimal CT simulation protocol selection as a function of patient size and treatment planning task. The optimal protocol is the one that delivers the minimum dose required to provide a CT simulation scan that yields accurate contours. Accurate treatment plans depend on accurate contours in order to conform the dose to actual tumor and normal organ positions. An image quality index, defined to characterize how simulation scan quality affects contour delineation, was developed and used to benchmark the contouring accuracy and treatment plan quality within the predication strategy. A clinical workflow was developed to select the optimal CT simulation protocols incorporating patient size, target delineation, and radiation dose efficiency. An experimental study using an anthropomorphic pelvis phantom with added-bolus layers was used to demonstrate how the proposed prediction strategy could be implemented and how the optimal CT simulation protocols could be selected for prostate cancer patients based on patient size and treatment planning task. Clinical IMRT prostate treatment plans for seven CT scans with varied image quality indices were separately optimized and compared to verify the trace of target and organ dosimetry coverage. Results: Based on the phantom study, the optimal image quality index for accurate manual prostate contouring was 4.4. The optimal tube

  9. A General Relativistic Magnetohydrodynamic Simulation of Jet Formation

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Richardson, G.; Koide, S.; Shibata, K.; Kudoh, T.; Hardee, P.; Fishman, G. J.

    2005-01-01

    We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation ofjet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity approx.0.3c) is created, as shown by previous two-dimensional axi- symmetric simulations with mirror symmetry at the equator. The three-dimensional simulation ran over 100 light crossing time units (T(sub s) = r(sub s)/c, where r(sub s = 2GM/c(sup 2), which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted owing in part to magnetic pressure from the twisting of the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3r(sub s). At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface ofthe thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outward with a wider angle than the initial jet. The widening of the jet is consistent with the outward-moving torsional Alfven waves. This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk because of the iack of streaming materiai from an accompanying star.

  10. Localized and generalized simulated wear of resin composites.

    PubMed

    Barkmeier, W W; Takamizawa, T; Erickson, R L; Tsujimoto, A; Latta, M; Miyazaki, M

    2015-01-01

    A laboratory study was conducted to examine the wear of resin composite materials using both a localized and generalized wear simulation model. Twenty specimens each of seven resin composites (Esthet•X HD [HD], Filtek Supreme Ultra [SU], Herculite Ultra [HU], SonicFill [SF], Tetric EvoCeram Bulk Fill [TB], Venus Diamond [VD], and Z100 Restorative [Z]) were subjected to a wear challenge of 400,000 cycles for both localized and generalized wear in a Leinfelder-Suzuki wear simulator (Alabama machine). The materials were placed in custom cylinder-shaped stainless steel fixtures. A stainless steel ball bearing (r=2.387 mm) was used as the antagonist for localized wear, and a stainless steel, cylindrical antagonist with a flat tip was used for generalized wear. A water slurry of polymethylmethacrylate (PMMA) beads was used as the abrasive media. A noncontact profilometer (Proscan 2100) with Proscan software was used to digitize the surface contours of the pretest and posttest specimens. AnSur 3D software was used for wear assessment. For localized testing, maximum facet depth (μm) and volume loss (mm(3)) were used to compare the materials. The mean depth of the facet surface (μm) and volume loss (mm(3)) were used for comparison of the generalized wear specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean depth of the facet for generalized wear. The results for localized wear simulation were as follows [mean (standard deviation)]: maximum facet depth (μm)--Z, 59.5 (14.7); HU, 99.3 (16.3); SU, 102.8 (13.8); HD, 110.2 (13.3); VD, 114.0 (10.3); TB, 125.5 (12.1); SF, 195.9 (16.9); volume loss (mm(3))--Z, 0.013 (0.002); SU, 0.026 (0.006); HU, 0.043 (0.008); VD, 0.057 (0.009); HD, 0.058 (0.014); TB, 0.061 (0.010); SF, 0.135 (0.024). Generalized wear simulation results were as follows: mean depth of facet (μm)--Z, 9.3 (3

  11. Event-driven Monte Carlo: Exact dynamics at all time scales for discrete-variable models

    NASA Astrophysics Data System (ADS)

    Mendoza-Coto, Alejandro; Díaz-Méndez, Rogelio; Pupillo, Guido

    2016-06-01

    We present an algorithm for the simulation of the exact real-time dynamics of classical many-body systems with discrete energy levels. In the same spirit of kinetic Monte Carlo methods, a stochastic solution of the master equation is found, with no need to define any other phase-space construction. However, unlike existing methods, the present algorithm does not assume any particular statistical distribution to perform moves or to advance the time, and thus is a unique tool for the numerical exploration of fast and ultra-fast dynamical regimes. By decomposing the problem in a set of two-level subsystems, we find a natural variable step size, that is well defined from the normalization condition of the transition probabilities between the levels. We successfully test the algorithm with known exact solutions for non-equilibrium dynamics and equilibrium thermodynamical properties of Ising-spin models in one and two dimensions, and compare to standard implementations of kinetic Monte Carlo methods. The present algorithm is directly applicable to the study of the real-time dynamics of a large class of classical Markovian chains, and particularly to short-time situations where the exact evolution is relevant.

  12. The Speedster-EXD- A New Event-Driven Hybrid CMOS X-ray Detector

    NASA Astrophysics Data System (ADS)

    Griffith, Christopher V.; Falcone, Abraham D.; Prieskorn, Zachary R.; Burrows, David N.

    2016-01-01

    The Speedster-EXD is a new 64×64 pixel, 40-μm pixel pitch, 100-μm depletion depth hybrid CMOS x-ray detector with the capability of reading out only those pixels containing event charge, thus enabling fast effective frame rates. A global charge threshold can be specified, and pixels containing charge above this threshold are flagged and read out. The Speedster detector has also been designed with other advanced in-pixel features to improve performance, including a low-noise, high-gain capacitive transimpedance amplifier that eliminates interpixel capacitance crosstalk (IPC), and in-pixel correlated double sampling subtraction to reduce reset noise. We measure the best energy resolution on the Speedster-EXD detector to be 206 eV (3.5%) at 5.89 keV and 172 eV (10.0%) at 1.49 keV. The average IPC to the four adjacent pixels is measured to be 0.25%±0.2% (i.e., consistent with zero). The pixel-to-pixel gain variation is measured to be 0.80%±0.03%, and a Monte Carlo simulation is applied to better characterize the contributions to the energy resolution.

  13. A generalized hard-sphere model for Monte Carlo simulation

    NASA Technical Reports Server (NTRS)

    Hassan, H. A.; Hash, David B.

    1993-01-01

    A new molecular model, called the generalized hard-sphere, or GHS model, is introduced. This model contains, as a special case, the variable hard-sphere model of Bird (1981) and is capable of reproducing all of the analytic viscosity coefficients available in the literature that are derived for a variety of interaction potentials incorporating attraction and repulsion. In addition, a new procedure for determining interaction potentials in a gas mixture is outlined. Expressions needed for implementing the new model in the direct simulation Monte Carlo methods are derived. This development makes it possible to employ interaction models that have the same level of complexity as used in Navier-Stokes calculations.

  14. Solute transport processes in flow-event-driven stream-aquifer interaction

    NASA Astrophysics Data System (ADS)

    Xie, Yueqing; Cook, Peter G.; Simmons, Craig T.

    2016-07-01

    The interaction between streams and groundwater controls key features of the stream hydrograph and chemograph. Since surface runoff is usually less saline than groundwater, flow events are usually accompanied by declines in stream salinity. In this paper, we use numerical modelling to show that, at any particular monitoring location: (i) the increase in stream stage associated with a flow event will precede the decrease in solute concentration (arrival time lag for solutes); and (ii) the decrease in stream stage following the flow peak will usually precede the subsequent return (increase) in solute concentration (return time lag). Both arrival time lag and return time lag increase with increasing wave duration. However, arrival time lag decreases with increasing wave amplitude, whereas return time lag increases. Furthermore, while arrival time lag is most sensitive to parameters that control river velocity (channel roughness and stream slope), return time lag is most sensitive to groundwater parameters (aquifer hydraulic conductivity, recharge rate, and dispersitivity). Additionally, the absolute magnitude of the decrease in river concentration is sensitive to both river and groundwater parameters. Our simulations also show that in-stream mixing is dominated by wave propagation and bank storage processes, and in-stream dispersion has a relatively minor effect on solute concentrations. This has important implications for spreading of contaminants released to streams. Our work also demonstrates that a high contribution of pre-event water (or groundwater) within the flow hydrograph can be caused by the combination of in-stream and bank storage exchange processes, and does not require transport of pre-event water through the catchment.

  15. An event-driven approach for studying gene block evolution in bacteria.

    PubMed

    Ream, David C; Bankapur, Asma R; Friedberg, Iddo

    2015-07-01

    Gene blocks are genes co-located on the chromosome. In many cases, gene blocks are conserved between bacterial species, sometimes as operons, when genes are co-transcribed. The conservation is rarely absolute: gene loss, gain, duplication, block splitting and block fusion are frequently observed. An open question in bacterial molecular evolution is that of the formation and breakup of gene blocks, for which several models have been proposed. These models, however, are not generally applicable to all types of gene blocks, and consequently cannot be used to broadly compare and study gene block evolution. To address this problem, we introduce an event-based method for tracking gene block evolution in bacteria. We show here that the evolution of gene blocks in proteobacteria can be described by a small set of events. Those include the insertion of genes into, or the splitting of genes out of a gene block, gene loss, and gene duplication. We show how the event-based method of gene block evolution allows us to determine the evolutionary rateand may be used to trace the ancestral states of their formation. We conclude that the event-based method can be used to help us understand the formation of these important bacterial genomic structures. The software is available under GPLv3 license on http://github.com/reamdc1/gene_block_evolution.git. Supplementary online material: http://iddo-friedberg.net/operon-evolution © The Author 2015. Published by Oxford University Press.

  16. A Distributed Laboratory for Event-Driven Coastal Prediction and Hazard Planning

    NASA Astrophysics Data System (ADS)

    Bogden, P.; Allen, G.; MacLaren, J.; Creager, G. J.; Flournoy, L.; Sheng, Y. P.; Graber, H.; Graves, S.; Conover, H.; Luettich, R.; Perrie, W.; Ramakrishnan, L.; Reed, D. A.; Wang, H. V.

    2006-12-01

    The 2005 Atlantic hurricane season was the most active in recorded history. Collectively, 2005 hurricanes caused more than 2,280 deaths and record damages of over 100 billion dollars. Of the storms that made landfall, Dennis, Emily, Katrina, Rita, and Wilma caused most of the destruction. Accurate predictions of storm-driven surge, wave height, and inundation can save lives and help keep recovery costs down, provided the information gets to emergency response managers in time. The information must be available well in advance of landfall so that responders can weigh the costs of unnecessary evacuation against the costs of inadequate preparation. The SURA Coastal Ocean Observing and Prediction (SCOOP) Program is a multi-institution collaboration implementing a modular, distributed service-oriented architecture for real time prediction and visualization of the impacts of extreme atmospheric events. The modular infrastructure enables real-time prediction of multi- scale, multi-model, dynamic, data-driven applications. SURA institutions are working together to create a virtual and distributed laboratory integrating coastal models, simulation data, and observations with computational resources and high speed networks. The loosely coupled architecture allows teams of computer and coastal scientists at multiple institutions to innovate complex system components that are interconnected with relatively stable interfaces. The operational system standardizes at the interface level to enable substantial innovation by complementary communities of coastal and computer scientists. This architectural philosophy solves a long-standing problem associated with the transition from research to operations. The SCOOP Program thereby implements a prototype laboratory consistent with the vision of a national, multi-agency initiative called the Integrated Ocean Observing System (IOOS). Several service- oriented components of the SCOOP enterprise architecture have already been designed and

  17. Characterization and development of an event-driven hybrid CMOS x-ray detector

    NASA Astrophysics Data System (ADS)

    Griffith, Christopher

    2015-06-01

    Hybrid CMOS detectors (HCD) have provided great benefit to the infrared and optical fields of astronomy, and they are poised to do the same for X-ray astronomy. Infrared HCDs have already flown on the Hubble Space Telescope and the Wide-Field Infrared Survey Explorer (WISE) mission and are slated to fly on the James Webb Space Telescope (JWST). Hybrid CMOS X-ray detectors offer low susceptibility to radiation damage, low power consumption, and fast readout time to avoid pile-up. The fast readout time is necessary for future high throughput X-ray missions. The Speedster-EXD X-ray HCD presented in this dissertation offers new in-pixel features and reduces known noise sources seen on previous generation HCDs. The Speedster-EXD detector makes a great step forward in the development of these detectors for future space missions. This dissertation begins with an overview of future X-ray space mission concepts and their detector requirements. The background on the physics of semiconductor devices and an explanation of the detection of X-rays with these devices will be discussed followed by a discussion on CCDs and CMOS detectors. Next, hybrid CMOS X-ray detectors will be explained including their advantages and disadvantages. The Speedster-EXD detector and its new features will be outlined including its ability to only read out pixels which contain X-ray events. Test stand design and construction for the Speedster-EXD detector is outlined and the characterization of each parameter on two Speedster-EXD detectors is detailed including read noise, dark current, interpixel capacitance crosstalk (IPC), and energy resolution. Gain variation is also characterized, and a Monte Carlo simulation of its impact on energy resolution is described. This analysis shows that its effect can be successfully nullified with proper calibration, which would be important for a flight mission. Appendix B contains a study of the extreme tidal disruption event, Swift J1644+57, to search for

  18. An event-driven approach for studying gene block evolution in bacteria

    PubMed Central

    Ream, David C.; Bankapur, Asma R.; Friedberg, Iddo

    2015-01-01

    Motivation: Gene blocks are genes co-located on the chromosome. In many cases, gene blocks are conserved between bacterial species, sometimes as operons, when genes are co-transcribed. The conservation is rarely absolute: gene loss, gain, duplication, block splitting and block fusion are frequently observed. An open question in bacterial molecular evolution is that of the formation and breakup of gene blocks, for which several models have been proposed. These models, however, are not generally applicable to all types of gene blocks, and consequently cannot be used to broadly compare and study gene block evolution. To address this problem, we introduce an event-based method for tracking gene block evolution in bacteria. Results: We show here that the evolution of gene blocks in proteobacteria can be described by a small set of events. Those include the insertion of genes into, or the splitting of genes out of a gene block, gene loss, and gene duplication. We show how the event-based method of gene block evolution allows us to determine the evolutionary rateand may be used to trace the ancestral states of their formation. We conclude that the event-based method can be used to help us understand the formation of these important bacterial genomic structures. Availability and implementation: The software is available under GPLv3 license on http://github.com/reamdc1/gene_block_evolution.git. Supplementary online material: http://iddo-friedberg.net/operon-evolution Contact: i.friedberg@miamioh.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:25717195

  19. Water Hammer Simulations of MMH Propellant - New Capability Demonstration of the Generalized Fluid Flow Simulation Program

    NASA Technical Reports Server (NTRS)

    Burkhardt, Z.; Ramachandran, N.; Majumdar, A.

    2017-01-01

    Fluid Transient analysis is important for the design of spacecraft propulsion system to ensure structural stability of the system in the event of sudden closing or opening of the valve. Generalized Fluid System Simulation Program (GFSSP), a general purpose flow network code developed at NASA/MSFC is capable of simulating pressure surge due to sudden opening or closing of valve when thermodynamic properties of real fluid are available for the entire range of simulation. Specifically GFSSP needs an accurate representation of pressure-density relationship in order to predict pressure surge during a fluid transient. Unfortunately, the available thermodynamic property programs such as REFPROP, GASP or GASPAK does not provide the thermodynamic properties of Monomethylhydrazine (MMH). This paper will illustrate the process used for building a customized table of properties of state variables from available properties and speed of sound that is required by GFSSP for simulation. Good agreement was found between the simulations and measured data. This method can be adopted for modeling flow networks and systems with other fluids whose properties are not known in detail in order to obtain general technical insight. Rigorous code validation of this approach will be done and reported at a future date.

  20. A generalized Poisson solver for first-principles device simulations

    SciTech Connect

    Bani-Hashemian, Mohammad Hossein; VandeVondele, Joost; Brück, Sascha; Luisier, Mathieu

    2016-01-28

    Electronic structure calculations of atomistic systems based on density functional theory involve solving the Poisson equation. In this paper, we present a plane-wave based algorithm for solving the generalized Poisson equation subject to periodic or homogeneous Neumann conditions on the boundaries of the simulation cell and Dirichlet type conditions imposed at arbitrary subdomains. In this way, source, drain, and gate voltages can be imposed across atomistic models of electronic devices. Dirichlet conditions are enforced as constraints in a variational framework giving rise to a saddle point problem. The resulting system of equations is then solved using a stationary iterative method in which the generalized Poisson operator is preconditioned with the standard Laplace operator. The solver can make use of any sufficiently smooth function modelling the dielectric constant, including density dependent dielectric continuum models. For all the boundary conditions, consistent derivatives are available and molecular dynamics simulations can be performed. The convergence behaviour of the scheme is investigated and its capabilities are demonstrated.

  1. Better Space Construction Decisions by Instructional Program Simulation Utilizing the Generalized Academic Simulation Programs.

    ERIC Educational Resources Information Center

    Apker, Wesley

    This school district utilized the generalized academic simulation programs (GASP) to assist in making decisions regarding the kinds of facilities that should be constructed at Pilchuck Senior High School. Modular scheduling was one of the basic educational parameters used in determining the number and type of facilities needed. The objectives of…

  2. Data Albums: An Event Driven Search, Aggregation and Curation Tool for Earth Science

    NASA Technical Reports Server (NTRS)

    Ramachandran, Rahul; Kulkarni, Ajinkya; Maskey, Manil; Bakare, Rohan; Basyal, Sabin; Li, Xiang; Flynn, Shannon

    2014-01-01

    One of the largest continuing challenges in any Earth science investigation is the discovery and access of useful science content from the increasingly large volumes of Earth science data and related information available. Approaches used in Earth science research such as case study analysis and climatology studies involve gathering discovering and gathering diverse data sets and information to support the research goals. Research based on case studies involves a detailed description of specific weather events using data from different sources, to characterize physical processes in play for a specific event. Climatology-based research tends to focus on the representativeness of a given event, by studying the characteristics and distribution of a large number of events. This allows researchers to generalize characteristics such as spatio-temporal distribution, intensity, annual cycle, duration, etc. To gather relevant data and information for case studies and climatology analysis is both tedious and time consuming. Current Earth science data systems are designed with the assumption that researchers access data primarily by instrument or geophysical parameter. Those who know exactly the datasets of interest can obtain the specific files they need using these systems. However, in cases where researchers are interested in studying a significant event, they have to manually assemble a variety of datasets relevant to it by searching the different distributed data systems. In these cases, a search process needs to be organized around the event rather than observing instruments. In addition, the existing data systems assume users have sufficient knowledge regarding the domain vocabulary to be able to effectively utilize their catalogs. These systems do not support new or interdisciplinary researchers who may be unfamiliar with the domain terminology. This paper presents a specialized search, aggregation and curation tool for Earth science to address these existing

  3. A General Simulator for Reaction-Based Biogeochemical Processes

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, George

    2006-02-01

    As more complex biogeochemical situations are being investigated (e.g., evolving reactivity, passivation of reactive surfaces, dissolution of sorbates), there is a growing need for biogeochemical simulators to flexibly and facilely address new reaction forms and rate laws. This paper presents an approach that accommodates this need to efficiently simulate general biogeochemical processes, while insulating the user from additional code development. The approach allows for the automatic extraction of fundamental reaction stoichiometry and thermodynamics from a standard chemistry database, and the symbolic entry of arbitrarily complex user-specified reaction forms, rate laws, and equilibria. The user-specified equilibrium and kinetic reactions (i.e., reactions not defined in the format of the standardized database) are interpreted by the Maple symbolic mathematical software package. FORTRAN 90 code is then generated by Maple for (1) the analytical Jacobian matrix (if preferred over the numerical Jacobian matrix) used in the Newton-Raphson solution procedure, and (2) the residual functions for user-specified equilibrium expressions and rate laws. Matrix diagonalization eliminates the need to conceptualize the system of reactions as a tableau, while identifying a minimum rank set of basis species with enhanced numerical convergence properties. The newly generated code, which is designed to operate in the BIOGEOCHEM biogeochemical simulator, is then compiled and linked into the BIOGEOCHEM executable. With these features, users can avoid recoding the simulator to accept new equilibrium expressions or kinetic rate laws, while still taking full advantage of the stoichiometry and thermodynamics provided by an existing chemical database. Thus, the approach introduces efficiencies in the specification of biogeochemical reaction networks and eliminates opportunities for mistakes in preparing input files and coding errors. Test problems are used to demonstrate the features of

  4. General Relativistic Radiative Transfer and General Relativistic MHD Simulations of Accretion and Outflows of Black Holes

    NASA Technical Reports Server (NTRS)

    Fuerst, Steven V.; Mizuno, Yosuke; Nishikawa, Ken-Ichi; Wu, Kinwah

    2007-01-01

    We have calculated the emission from relativistic flows in black hole systems using a fully general relativistic radiative transfer, with flow structures obtained by general relativistic magnetohydrodynamic simulations. We consider thermal free-free emission and thermal synchrotron emission. Bright filament-like features are found protruding (visually) from the accretion disk surface, which are enhancements of synchrotron emission when the magnetic field is roughly aligned with the line-of-sight in the co-moving frame. The features move back and forth as the accretion flow evolves, but their visibility and morphology are robust. We propose that variations and location drifts of the features are responsible for certain X-ray quasi-periodic oscillations (QPOs) observed in black-hole X-ray binaries.

  5. A generalized well management scheme for reservoir simulation

    SciTech Connect

    Fang, W.Y.; Lo, K.K.

    1995-12-31

    A new generalized well management scheme has been formulated to maximize oil production under multiple facility constraints. The scheme integrates reserve performance, wellbore hydraulics, surface facility constraints and lift-gas allocation o maximize oil production. It predicts well performance based on up-to-date hydraulics and reservoir conditions. The scheme has been implemented in a black oil simulator by using Separable programming and Simplex algorithm. This production optimization scheme has been applied to two full-field models. The oil production of these two full-field models is limited by water, gas and liquid haling limits at both field- and flow station-levels. The gas production is limited by injectivity as well as gas handling limits. For a 12-year production forecast on Field A, the new scheme increased oil production by 3 to 9%. For a 12-year production forecast on field B, the new scheme increased oil production by 7 to 9%.

  6. General and efficient simulation of pulse EPR spectra.

    PubMed

    Stoll, Stefan; Britt, R David

    2009-08-21

    We present a rather general and efficient method of simulating electron-spin echo spectra for spin systems where the microwave frequency does not simultaneously excite EPR transitions that share a common level. The approach can handle arbitrary pulse sequences with microwave pulses of arbitrary length and strength. The signal is computed as a sum over signals from the electron coherence transfer pathways contributing to the detected echo. For each pathway, amplitudes and frequencies of the signal components are computed and used to construct a spectral histogram from which the time-domain signal is obtained. For multinuclear spin systems, the nuclear subspace is factorized to accelerate the computation. The method is also applicable to high electron spin systems with significant zero-field splitting and to pulse electron-nuclear double resonance experiments. The method is implemented in the software package EasySpin, and several illustrative calculations are shown.

  7. An Event Driven Read-Out System for a Novel PET Scanner With Compton Enhanced 3-D Gamma Reconstruction

    NASA Astrophysics Data System (ADS)

    Dragone, A.; Corsi, F.; Marzocca, C.; Losito, P.; Pasqua, D.; Nappi, E.; De Leo, R.; Seguinot, J.; Braem, A.; Chesi, E.; Joram, C.; Weilhammer, P.; Garibaldi, F.; Zaidi, H.

    2006-06-01

    The design of a data acquisition system (DAQ) for a novel positron emission tomography (PET) scanner is reported. The PET system, based on long axially oriented scintillation crystals, readout by hybrid photon detectors (HPD), allows 3-D parallax-error free Compton enhanced gamma reconstruction. The DAQ system is composed of several readout cards, each one associated with a module of the PET scanner, and of a main card that controls the whole system. Using fast triggering signals from the silicon sensor back-planes, the main card performs the coincidence analysis and, in case of coincidence, it enables the readout of the two modules involved. The other modules are left free to perform new acquisitions. This concept based on several independent, event-driven and parallel readout chains, drastically reduces the acquisition dead time. Each enabled readout card digitizes, encodes and stores data from the associated module. Data are stored in a local FIFO and then are transferred through a network into a single computer. The system is designed according to the specifications of the IDEAS VaTaGP5 chip. Each readout card is able to accommodate all the chip readout modes and the test procedures and can be used as a standalone readout system that allows reading out up to 16 daisy chained chips per channel. The DAQ system here reported, designed for a two module demonstrator setup, was developed to study and optimize the essential design parameters.

  8. Event-driven, pattern-based methodology for cost-effective development of standardized personal health devices.

    PubMed

    Martínez-Espronceda, Miguel; Trigo, Jesús D; Led, Santiago; Barrón-González, H Gilberto; Redondo, Javier; Baquero, Alfonso; Serrano, Luis

    2014-11-01

    Experiences applying standards in personal health devices (PHDs) show an inherent trade-off between interoperability and costs (in terms of processing load and development time). Therefore, reducing hardware and software costs as well as time-to-market is crucial for standards adoption. The ISO/IEEE11073 PHD family of standards (also referred to as X73PHD) provides interoperable communication between PHDs and aggregators. Nevertheless, the responsibility of achieving inexpensive implementations of X73PHD in limited resource microcontrollers falls directly on the developer. Hence, the authors previously presented a methodology based on patterns to implement X73-compliant PHDs into devices with low-voltage low-power constraints. That version was based on multitasking, which required additional features and resources. This paper therefore presents an event-driven evolution of the patterns-based methodology for cost-effective development of standardized PHDs. The results of comparing between the two versions showed that the mean values of decrease in memory consumption and cycles of latency are 11.59% and 45.95%, respectively. In addition, several enhancements in terms of cost-effectiveness and development time can be derived from the new version of the methodology. Therefore, the new approach could help in producing cost-effective X73-compliant PHDs, which in turn could foster the adoption of standards.

  9. Event driven executive

    NASA Technical Reports Server (NTRS)

    Tulpule, Bhalchandra R. (Inventor); Collins, Robert E. (Inventor); Cheetham, John (Inventor); Cornwell, Smith (Inventor)

    1990-01-01

    Tasks may be planned for execution on a single processor or are split up by the designer for execution among a plurality of signal processors. The tasks are modeled using a design aid called a precedence graph, from which a dependency table and a prerequisite table are established for reference within each processor. During execution, at the completion of a given task, an end of task interrupt is provided from any processor which has completed a task to any and all other processors including itself in which completion of that task is a prerequisite for commencement of any dependent tasks. The relevant updated data may be transferred by the processor either before or after signalling task completion to the processors needing the updated data prior to commencing execution of the dependent tasks. Coherency may be ensured, however, by sending the data before the interrupt. When the end of task interrupt is received in a processor, its dependency table is consulted to determine those tasks dependent upon completion of the task which has just been signalled as completed, and task dependency signals indicative thereof are provided and stored in a current status list of a prerequisite table. The current status of all current prerequisites are compared to the complete prerequisites listed for all affected tasks and those tasks for which the comparison indicates that all prerequisites have been met are queued for execution in a selected order.

  10. Amyloid oligomer structure characterization from simulations: A general method

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong H.; Li, Mai Suan; Derreumaux, Philippe

    2014-03-01

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  11. Amyloid oligomer structure characterization from simulations: a general method.

    PubMed

    Nguyen, Phuong H; Li, Mai Suan; Derreumaux, Philippe

    2014-03-07

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  12. Amyloid oligomer structure characterization from simulations: A general method

    SciTech Connect

    Nguyen, Phuong H.; Li, Mai Suan

    2014-03-07

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ{sub 9−40}, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  13. Diffusion microscopist simulator: a general Monte Carlo simulation system for diffusion magnetic resonance imaging.

    PubMed

    Yeh, Chun-Hung; Schmitt, Benoît; Le Bihan, Denis; Li-Schlittgen, Jing-Rebecca; Lin, Ching-Po; Poupon, Cyril

    2013-01-01

    This article describes the development and application of an integrated, generalized, and efficient Monte Carlo simulation system for diffusion magnetic resonance imaging (dMRI), named Diffusion Microscopist Simulator (DMS). DMS comprises a random walk Monte Carlo simulator and an MR image synthesizer. The former has the capacity to perform large-scale simulations of Brownian dynamics in the virtual environments of neural tissues at various levels of complexity, and the latter is flexible enough to synthesize dMRI datasets from a variety of simulated MRI pulse sequences. The aims of DMS are to give insights into the link between the fundamental diffusion process in biological tissues and the features observed in dMRI, as well as to provide appropriate ground-truth information for the development, optimization, and validation of dMRI acquisition schemes for different applications. The validity, efficiency, and potential applications of DMS are evaluated through four benchmark experiments, including the simulated dMRI of white matter fibers, the multiple scattering diffusion imaging, the biophysical modeling of polar cell membranes, and the high angular resolution diffusion imaging and fiber tractography of complex fiber configurations. We expect that this novel software tool would be substantially advantageous to clarify the interrelationship between dMRI and the microscopic characteristics of brain tissues, and to advance the biophysical modeling and the dMRI methodologies.

  14. Generalized Fluid System Simulation Program, Version 5.0-Educational

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.

    2011-01-01

    The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors and external body forces such as gravity and centrifugal. The thermofluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the point, drag and click method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids and 21 different resistance/source options are provided for modeling momentum sources or sinks in the branches. This Technical Memorandum illustrates the application and verification of the code through 12 demonstrated example problems.

  15. Generalized Fluid System Simulation Program, Version 6.0

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.; LeClair, A. C.; Moore, A.; Schallhorn, P. A.

    2013-01-01

    The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependant flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors and external body forces such as gravity and centrifugal. The thermo-fluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids, and 24 different resistance/source options are provided for modeling momentum sources or sinks in the branches. This Technical Memorandum illustrates the application and verification of the code through 25 demonstrated example problems.

  16. Generalized Fluid System Simulation Program (GFSSP) - Version 6

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok; LeClair, Andre; Moore, Ric; Schallhorn, Paul

    2015-01-01

    The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors, flow control valves and external body forces such as gravity and centrifugal. The thermo-fluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids, and 24 different resistance/source options are provided for modeling momentum sources or sinks in the branches. Users can introduce new physics, non-linear and time-dependent boundary conditions through user-subroutine.

  17. Simulation of Codman's paradox reveals a general law of motion.

    PubMed

    Cheng, Pei Lai

    2006-01-01

    Codman's paradox refers to a specific pattern of motion at the shoulder joint. It asked how a mysterious axial rotation about the longitudinal axis of the arm occurred during two or three sequential arm rotations that did not involve rotation about the long-axis. The objective of this paper was to find how the mysterious axial rotation occurred in the Codman's paradox. First, Codman's paradox and Codman's rotation were defined in general situations that involved arm rotations about orthogonal axes starting from the neutral attitude as well as rotations about non-orthogonal axes and starting from non-neutral attitudes. Then a general law of motion was proposed to answer the question of the Codman's paradox, which is stated as when the long-axis of the arm performs a closed-loop motion by three sequential rotations defined as Codman's rotation, it produces an equivalent axial rotation angle about the long-axis. The equivalent axial rotation angle equals the angle of swing-the second rotation in the three sequential long-axis rotations. Validity of the proposed law of motion is demonstrated by computer simulation of various Codman's rotations. Clinical relevance of the proposed law of motion is also discussed in the paper.

  18. Hospitable archean climates simulated by a general circulation model.

    PubMed

    Wolf, E T; Toon, O B

    2013-07-01

    Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model.

  19. Respective influence of veterinarians and local institutional stakeholders on the event-driven surveillance system for bovine brucellosis in France.

    PubMed

    Bronner, Anne; Morignat, Eric; Calavas, Didier

    2015-08-01

    The event-driven surveillance system for bovine brucellosis implemented in France aims to ensure the early detection of cases of bovine brucellosis, a disease of which the country has been declared free since 2005. It consists of mandatory notification of bovine abortions by farmers and veterinarians. However, as underlined by a previous qualitative study, several factors influence the decision-making process of actors in the field. This process is particularly influenced by the level of cooperation between institutional stakeholders in their département (a French département being an administrative and territorial unit), veterinarians and farmers. In this context, the objectives of this study were 1) to quantify the respective influence of veterinarians and all local institutional stakeholders on the proportion of notifying farmers and identify which actors have most influence on farmers' decisions; 2) to analyse whether the influence of veterinarians is correlated with that of local institutional stakeholders. In addition to factors relating to the farm itself (production type and herd size), the proportion of notifying farmers was influenced by the number of veterinarians per practice and the veterinary practice's membership of a technical association. This proportion was also influenced by unknown factors relating to the veterinary practice and, to a lesser extent, the département in which the farm was located. There was no correlation between variability in the proportion of notifying farmers among veterinary practices per département and the effect of the département itself. To our knowledge, this is the first study to quantify the influence of veterinarians and local institutional stakeholders on the notification process for a mandatory disease. In addition to carrying out regulatory interventions, veterinarians play a major role in encouraging farmers to participate in the surveillance systems. The results of this study, combined with a previous

  20. An Event-Driven Classifier for Spiking Neural Networks Fed with Synthetic or Dynamic Vision Sensor Data.

    PubMed

    Stromatias, Evangelos; Soto, Miguel; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabé

    2017-01-01

    This paper introduces a novel methodology for training an event-driven classifier within a Spiking Neural Network (SNN) System capable of yielding good classification results when using both synthetic input data and real data captured from Dynamic Vision Sensor (DVS) chips. The proposed supervised method uses the spiking activity provided by an arbitrary topology of prior SNN layers to build histograms and train the classifier in the frame domain using the stochastic gradient descent algorithm. In addition, this approach can cope with leaky integrate-and-fire neuron models within the SNN, a desirable feature for real-world SNN applications, where neural activation must fade away after some time in the absence of inputs. Consequently, this way of building histograms captures the dynamics of spikes immediately before the classifier. We tested our method on the MNIST data set using different synthetic encodings and real DVS sensory data sets such as N-MNIST, MNIST-DVS, and Poker-DVS using the same network topology and feature maps. We demonstrate the effectiveness of our approach by achieving the highest classification accuracy reported on the N-MNIST (97.77%) and Poker-DVS (100%) real DVS data sets to date with a spiking convolutional network. Moreover, by using the proposed method we were able to retrain the output layer of a previously reported spiking neural network and increase its performance by 2%, suggesting that the proposed classifier can be used as the output layer in works where features are extracted using unsupervised spike-based learning methods. In addition, we also analyze SNN performance figures such as total event activity and network latencies, which are relevant for eventual hardware implementations. In summary, the paper aggregates unsupervised-trained SNNs with a supervised-trained SNN classifier, combining and applying them to heterogeneous sets of benchmarks, both synthetic and from real DVS chips.

  1. Extension of Generalized Fluid System Simulation Program's Fluid Property Database

    NASA Technical Reports Server (NTRS)

    Patel, Kishan

    2011-01-01

    This internship focused on the development of additional capabilities for the General Fluid Systems Simulation Program (GFSSP). GFSSP is a thermo-fluid code used to evaluate system performance by a finite volume-based network analysis method. The program was developed primarily to analyze the complex internal flow of propulsion systems and is capable of solving many problems related to thermodynamics and fluid mechanics. GFSSP is integrated with thermodynamic programs that provide fluid properties for sub-cooled, superheated, and saturation states. For fluids that are not included in the thermodynamic property program, look-up property tables can be provided. The look-up property tables of the current release version can only handle sub-cooled and superheated states. The primary purpose of the internship was to extend the look-up tables to handle saturated states. This involves a) generation of a property table using REFPROP, a thermodynamic property program that is widely used, and b) modifications of the Fortran source code to read in an additional property table containing saturation data for both saturated liquid and saturated vapor states. Also, a method was implemented to calculate the thermodynamic properties of user-fluids within the saturation region, given values of pressure and enthalpy. These additions required new code to be written, and older code had to be adjusted to accommodate the new capabilities. Ultimately, the changes will lead to the incorporation of this new capability in future versions of GFSSP. This paper describes the development and validation of the new capability.

  2. Simulations of JWST/NIRISS Modes for General Observers

    NASA Astrophysics Data System (ADS)

    Gosmeyer, Catherine; Albert, Loic; Brammer, Gabriel; Filippazzo, Joe; Fullerton, Alexander W.; Greenbaum, Alexandra; Rowe, Jason; SAHLMANN, JOHANNES; Sivaramakrishnan, Anand; Thatte, Deepashri G.; Volk, Kevin

    2017-06-01

    The Near-Infrared Imager and Slitless Spectrograph (NIRISS) is a contribution of the Canadian Space Agency to the James Webb Space Telescope (JWST). NIRISS complements the other near-infrared science instruments on-board JWST by providing capabilities for (a) low-resolution grism spectroscopy between 0.8 and 2.2 µm over the entire field of view, with the possibility of observing the same scene with orthogonal dispersion directions to disentangle blended objects; (b) medium-resolution grism spectroscopy between 0.6 and 2.8 µm that has been optimized to provide high spectrophotometric stability for time-series observations of transiting exoplanets; (c) aperture masking interferometry that provides high angular resolution of 70 - 400 mas at wavelengths between 2.8 and 4.8 µm and (d) parallel imaging through a set of filters that are closely matched to NIRCam's.In this poster, we present realistic simulations of observations through each of these modes in order to stimulate the General Observer community to consider how NIRISS might help to achieve their scientific goals.

  3. Sensitivity simulations of superparameterised convection in a general circulation model

    NASA Astrophysics Data System (ADS)

    Rybka, Harald; Tost, Holger

    2015-04-01

    Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation. This study presents different simulations of an adapted Earth System Model (ESM) connected to a CRM which acts as a superparameterisation. Simulations have been performed with the ECHAM/MESSy atmospheric chemistry (EMAC) model comparing conventional GCM runs (including convection and large-scale cloud parameterisations) with the improved superparameterised EMAC (SP-EMAC) modeling one year with prescribed sea surface temperatures and sea ice content. The sensitivity of atmospheric temperature, precipiation patterns, cloud amount and types is observed changing the embedded CRM represenation (orientation, width, no. of CRM cells, 2D vs. 3D). Additionally, we also evaluate the radiation balance with the new model configuration, and systematically analyse the impact of tunable parameters on the radiation budget and hydrological cycle. Furthermore, the subgrid

  4. GLoBES: General Long Baseline Experiment Simulator

    NASA Astrophysics Data System (ADS)

    Huber, Patrick; Kopp, Joachim; Lindner, Manfred; Rolinec, Mark; Winter, Walter

    2007-09-01

    GLoBES (General Long Baseline Experiment Simulator) is a flexible software package to simulate neutrino oscillation long baseline and reactor experiments. On the one hand, it contains a comprehensive abstract experiment definition language (AEDL), which allows to describe most classes of long baseline experiments at an abstract level. On the other hand, it provides a C-library to process the experiment information in order to obtain oscillation probabilities, rate vectors, and Δχ-values. Currently, GLoBES is available for GNU/Linux. Since the source code is included, the port to other operating systems is in principle possible. GLoBES is an open source code that has previously been described in Computer Physics Communications 167 (2005) 195 and in Ref. [7]). The source code and a comprehensive User Manual for GLoBES v3.0.8 is now available from the CPC Program Library as described in the Program Summary below. The home of GLobES is http://www.mpi-hd.mpg.de/~globes/. Program summaryProgram title: GLoBES version 3.0.8 Catalogue identifier: ADZI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 145 295 No. of bytes in distributed program, including test data, etc.: 1 811 892 Distribution format: tar.gz Programming language: C Computer: GLoBES builds and installs on 32bit and 64bit Linux systems Operating system: 32bit or 64bit Linux RAM: Typically a few MBs Classification: 11.1, 11.7, 11.10 External routines: GSL—The GNU Scientific Library, www.gnu.org/software/gsl/ Nature of problem: Neutrino oscillations are now established as the leading flavor transition mechanism for neutrinos. In a long history of many experiments, see, e.g., [1], two oscillation frequencies have been identified: The fast atmospheric

  5. Generalized Fluid System Simulation Program, Version 6.0

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.; LeClair, A. C.; Moore, R.; Schallhorn, P. A.

    2016-01-01

    The Generalized Fluid System Simulation Program (GFSSP) is a general purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors, and external body forces such as gravity and centrifugal. The thermofluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. Two thermodynamic property programs (GASP/WASP and GASPAK) provide required thermodynamic and thermophysical properties for 36 fluids: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutene, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride, ammonia, hydrogen peroxide, and air. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. The users can also supply property tables for fluids that are not in the library. Twenty-four different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include pipe flow, flow through a restriction, noncircular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct

  6. NON-SPATIAL CALIBRATIONS OF A GENERAL UNIT MODEL FOR ECOSYSTEM SIMULATIONS. (R825792)

    EPA Science Inventory

    General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the d...

  7. NON-SPATIAL CALIBRATIONS OF A GENERAL UNIT MODEL FOR ECOSYSTEM SIMULATIONS. (R827169)

    EPA Science Inventory

    General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the d...

  8. NON-SPATIAL CALIBRATIONS OF A GENERAL UNIT MODEL FOR ECOSYSTEM SIMULATIONS. (R827169)

    EPA Science Inventory

    General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the d...

  9. NON-SPATIAL CALIBRATIONS OF A GENERAL UNIT MODEL FOR ECOSYSTEM SIMULATIONS. (R825792)

    EPA Science Inventory

    General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the d...

  10. Generalized simulation technique for turbojet engine system analysis

    NASA Technical Reports Server (NTRS)

    Seldner, K.; Mihaloew, J. R.; Blaha, R. J.

    1972-01-01

    A nonlinear analog simulation of a turbojet engine was developed. The purpose of the study was to establish simulation techniques applicable to propulsion system dynamics and controls research. A schematic model was derived from a physical description of a J85-13 turbojet engine. Basic conservation equations were applied to each component along with their individual performance characteristics to derive a mathematical representation. The simulation was mechanized on an analog computer. The simulation was verified in both steady-state and dynamic modes by comparing analytical results with experimental data obtained from tests performed at the Lewis Research Center with a J85-13 engine. In addition, comparison was also made with performance data obtained from the engine manufacturer. The comparisons established the validity of the simulation technique.

  11. Seasonal changes in the atmospheric heat balance simulated by the GISS general circulation model

    NASA Technical Reports Server (NTRS)

    Stone, P. H.; Chow, S.; Helfand, H. M.; Quirk, W. J.; Somerville, R. C. J.

    1975-01-01

    Tests of the ability of numerical general circulation models to simulate the atmosphere have focussed so far on simulations of the January climatology. These models generally present boundary conditions such as sea surface temperature, but this does not prevent testing their ability to simulate seasonal changes in atmospheric processes that accompany presented seasonal changes in boundary conditions. Experiments to simulate changes in the zonally averaged heat balance are discussed since many simplified models of climatic processes are based solely on this balance.

  12. A Generalized Computer Simulation Language for Naval Systems Modeling.

    DTIC Science & Technology

    1981-06-30

    FORTRAN-based software for statistical methodology and optimization. NAVMAP (Naval Modeling and Analysis Program) is intended to serve as the basis for a consistent simulation modeling approach among naval research laboratories. (Author)

  13. General approach to boat simulation in virtual reality systems

    NASA Astrophysics Data System (ADS)

    Aranov, Vladislav Y.; Belyaev, Sergey Y.

    2002-02-01

    The paper is dedicated to real time simulation of sport boats, particularly a kayak and high-speed skimming boat, for training goals. This training is issue of the day, since kayaking and riding a high-speed skimming boat are both extreme sports. Participating in such types of competitions puts sportsmen into danger, particularly due to rapids, waterfalls, different water streams, and other obstacles. In order to make the simulation realistic, it is necessary to calculate data for at least 30 frames per second. These calculations may take not more than 5% CPU time, because very time-consuming 3D rendering process takes the rest - 95% CPU time. This paper describes an approach for creating minimal boat simulator models that satisfy the mentioned requirements. Besides, this approach can be used for other watercraft models of this kind.

  14. Projectile General Motion in a Vacuum and a Spreadsheet Simulation

    ERIC Educational Resources Information Center

    Benacka, Jan

    2015-01-01

    This paper gives the solution and analysis of projectile motion in a vacuum if the launch and impact heights are not equal. Formulas for the maximum horizontal range and the corresponding angle are derived. An Excel application that simulates the motion is also presented, and the result of an experiment in which 38 secondary school students…

  15. Verifying Algorithms for Autonomous Aircraft by Simulation Generalities and Example

    NASA Technical Reports Server (NTRS)

    White, Allan L.

    2010-01-01

    An open question in Air Traffic Management is what procedures can be validated by simulation where the simulation shows that the probability of undesirable events is below the required level at some confidence level. The problem is including enough realism to be convincing while retaining enough efficiency to run the large number of trials needed for high confidence. The paper first examines the probabilistic interpretation of a typical requirement by a regulatory agency and computes the number of trials needed to establish the requirement at an equivalent confidence level. Since any simulation is likely to consider only one type of event and there are several types of events, the paper examines under what conditions this separate consideration is valid. The paper establishes a separation algorithm at the required confidence level where the aircraft operates under feedback control as is subject to perturbations. There is a discussion where it is shown that a scenario three of four orders of magnitude more complex is feasible. The question of what can be validated by simulation remains open, but there is reason to be optimistic.

  16. Projectile General Motion in a Vacuum and a Spreadsheet Simulation

    ERIC Educational Resources Information Center

    Benacka, Jan

    2015-01-01

    This paper gives the solution and analysis of projectile motion in a vacuum if the launch and impact heights are not equal. Formulas for the maximum horizontal range and the corresponding angle are derived. An Excel application that simulates the motion is also presented, and the result of an experiment in which 38 secondary school students…

  17. Generalized Maintenance Trainer Simulator: Development of Hardware and Software. Final Report.

    ERIC Educational Resources Information Center

    Towne, Douglas M.; Munro, Allen

    A general purpose maintenance trainer, which has the potential to simulate a wide variety of electronic equipments without hardware changes or new computer programs, has been developed and field tested by the Navy. Based on a previous laboratory model, the Generalized Maintenance Trainer Simulator (GMTS) is a relatively low cost trainer that…

  18. On the simulation of the oceanic general circulation

    NASA Technical Reports Server (NTRS)

    Mintz, Y.

    1979-01-01

    Two global ocean simulations based on the physics of a highly viscous ocean are discussed, one having realistic atmospheric functions for calculating the thermal forcing of the ocean. The velocity field of this model compares reasonably well with the relatively small amount of real data available. Temperature and heat budget components of the model reproduce best the equatorial band of heating. A simulation based upon the physics of a weakly viscous ocean is described, which produces the correct pattern of isotherms. This model has not yet been run to thermal equilibrium. The Gulf Stream and eddies and their influence on the oceanic and atmospheric heat budgets are discussed in the terms of their importance in coupled ocean-atmosphere models.

  19. SimulaTEM: multislice simulations for general objects.

    PubMed

    Gómez-Rodríguez, A; Beltrán-Del-Río, L M; Herrera-Becerra, R

    2010-01-01

    In this work we present the program SimulaTEM for the simulation of high resolution micrographs and diffraction patterns. This is a program based on the multislice approach that does not assume a periodic object. It can calculate images from finite objects, from amorphous samples, from crystals, quasicrystals, grain boundaries, nanoparticles or arbitrary objects provided the coordinates of all the atoms can be supplied. Copyright 2009 Elsevier B.V. All rights reserved.

  20. SimGen: A General Simulation Method for Large Systems.

    PubMed

    Taylor, William R

    2017-02-03

    SimGen is a stand-alone computer program that reads a script of commands to represent complex macromolecules, including proteins and nucleic acids, in a structural hierarchy that can then be viewed using an integral graphical viewer or animated through a high-level application programming interface in C++. Structural levels in the hierarchy range from α-carbon or phosphate backbones through secondary structure to domains, molecules, and multimers with each level represented in an identical data structure that can be manipulated using the application programming interface. Unlike most coarse-grained simulation approaches, the higher-level objects represented in SimGen can be soft, allowing the lower-level objects that they contain to interact directly. The default motion simulated by SimGen is a Brownian-like diffusion that can be set to occur across all levels of representation in the hierarchy. Links can also be defined between objects, which, when combined with large high-level random movements, result in an effective search strategy for constraint satisfaction, including structure prediction from predicted pairwise distances. The implementation of SimGen makes use of the hierarchic data structure to avoid unnecessary calculation, especially for collision detection, allowing it to be simultaneously run and viewed on a laptop computer while simulating large systems of over 20,000 objects. It has been used previously to model complex molecular interactions including the motion of a myosin-V dimer "walking" on an actin fibre, RNA stem-loop packing, and the simulation of cell motion and aggregation. Several extensions to this original functionality are described.

  1. Simulation based education - models for teaching surgical skills in general practice.

    PubMed

    Sinha, Sankar; Cooling, Nicholas

    2012-12-01

    Simulation based education is an accepted method of teaching procedural skills in both undergraduate and postgraduate medical education. There is an increasing need for developing authentic simulation models for use in general practice training. This article describes the preparation of three simulation models to teach general practice registrars basic surgical skills, including excision of a sebaceous cyst and debridement and escharectomy of chronic wounds. The role of deliberate practise in improving performance of procedural skills with simulation based education is well established. The simulation models described are inexpensive, authentic and can be easily prepared. They have been used in general practice education programs with positive feedback from participants and could potentially be used as in-practice teaching tools by general practitioner supervisors. Importantly, no simulation can exactly replicate the actual clinical situation, especially when complications arise. It is important that registrars are provided with adequate supervision when initially applying these surgical skills to patients.

  2. GENERAL REQUIREMENTS FOR SIMULATION MODELS IN WASTE MANAGEMENT

    SciTech Connect

    Miller, Ian; Kossik, Rick; Voss, Charlie

    2003-02-27

    Most waste management activities are decided upon and carried out in a public or semi-public arena, typically involving the waste management organization, one or more regulators, and often other stakeholders and members of the public. In these environments, simulation modeling can be a powerful tool in reaching a consensus on the best path forward, but only if the models that are developed are understood and accepted by all of the parties involved. These requirements for understanding and acceptance of the models constrain the appropriate software and model development procedures that are employed. This paper discusses requirements for both simulation software and for the models that are developed using the software. Requirements for the software include transparency, accessibility, flexibility, extensibility, quality assurance, ability to do discrete and/or continuous simulation, and efficiency. Requirements for the models that are developed include traceability, transparency, credibility/validity, and quality control. The paper discusses these requirements with specific reference to the requirements for performance assessment models that are used for predicting the long-term safety of waste disposal facilities, such as the proposed Yucca Mountain repository.

  3. Generalized simulated tempering for exploring strong phase transitions.

    PubMed

    Kim, Jaegil; Straub, John E

    2010-10-21

    An extension of the simulation tempering algorithm is proposed. It is shown to be particularly suited to the exploration of first-order phase transition systems characterized by the backbending or S-loop in the statistical temperature or a microcanonical caloric curve. A guided Markov process in an auxiliary parameter space systematically combines a set of parametrized Tsallis-weight ensemble simulations, which are targeted to transform unstable or metastable energy states of canonical ensembles into stable ones and smoothly join ordered and disordered phases across phase transition regions via a succession of unimodal energy distributions. The inverse mapping between the sampling weight and the effective temperature enables an optimal selection of relevant Tsallis-weight parameters. A semianalytic expression for the biasing weight in parameter space is adaptively updated "on the fly" during the simulation to achieve rapid convergence. Accelerated tunneling transitions with a comprehensive sampling for phase-coexistent states are explicitly demonstrated in systems subject to strong hysteresis including Potts and Ising spin models and a 147 atom Lennard-Jones cluster.

  4. BIRD: A general interface for sparse distributed memory simulators

    NASA Technical Reports Server (NTRS)

    Rogers, David

    1990-01-01

    Kanerva's sparse distributed memory (SDM) has now been implemented for at least six different computers, including SUN3 workstations, the Apple Macintosh, and the Connection Machine. A common interface for input of commands would both aid testing of programs on a broad range of computer architectures and assist users in transferring results from research environments to applications. A common interface also allows secondary programs to generate command sequences for a sparse distributed memory, which may then be executed on the appropriate hardware. The BIRD program is an attempt to create such an interface. Simplifying access to different simulators should assist developers in finding appropriate uses for SDM.

  5. Projectile general motion in a vacuum and a spreadsheet simulation

    NASA Astrophysics Data System (ADS)

    Benacka, Jan

    2015-01-01

    This paper gives the solution and analysis of projectile motion in a vacuum if the launch and impact heights are not equal. Formulas for the maximum horizontal range and the corresponding angle are derived. An Excel application that simulates the motion is also presented, and the result of an experiment in which 38 secondary school students developed the application and investigated the system is given. A questionnaire survey was carried out to find out whether the students found the lessons interesting, learned new skills and wanted to model projectile motion in the air as an example of more realistic motion. The results are discussed.

  6. A General Simulation Method for Multiple Bodies in Proximate Flight

    NASA Technical Reports Server (NTRS)

    Meakin, Robert L.

    2003-01-01

    Methods of unsteady aerodynamic simulation for an arbitrary number of independent bodies flying in close proximity are considered. A novel method to efficiently detect collision contact points is described. A method to compute body trajectories in response to aerodynamic loads, applied loads, and inter-body collisions is also given. The physical correctness of the methods are verified by comparison to a set of analytic solutions. The methods, combined with a Navier-Stokes solver, are used to demonstrate the possibility of predicting the unsteady aerodynamics and flight trajectories of moving bodies that involve rigid-body collisions.

  7. Optimal generalized multistep integration formulae for real-time digital simulation

    NASA Technical Reports Server (NTRS)

    Moerder, D. D.; Halyo, N.

    1985-01-01

    The problem of discretizing a dynamical system for real-time digital simulation is considered. Treating the system and its simulation as stochastic processes leads to a statistical characterization of simulator fidelity. A plant discretization procedure based on an efficient matrix generalization of explicit linear multistep discrete integration formulae is introduced, which minimizes a weighted sum of the mean squared steady-state and transient error between the system and simulator outputs.

  8. Plasma Jet Simulations Using a Generalized Ohm's Law

    NASA Technical Reports Server (NTRS)

    Ebersohn, Frans; Shebalin, John V.; Girimaji, Sharath S.

    2012-01-01

    Plasma jets are important physical phenomena in astrophysics and plasma propulsion devices. A currently proposed dual jet plasma propulsion device to be used for ISS experiments strongly resembles a coronal loop and further draws a parallel between these physical systems [1]. To study plasma jets we use numerical methods that solve the compressible MHD equations using the generalized Ohm s law [2]. Here, we will discuss the crucial underlying physics of these systems along with the numerical procedures we utilize to study them. Recent results from our numerical experiments will be presented and discussed.

  9. Scaling of asymmetric magnetic reconnection: General theory and collisional simulations

    SciTech Connect

    Cassak, P. A.; Shay, M. A.

    2007-10-15

    A Sweet-Parker-type scaling analysis for asymmetric antiparallel reconnection (in which the reconnecting magnetic field strengths and plasma densities are different on opposite sides of the dissipation region) is performed. Scaling laws for the reconnection rate, outflow speed, the density of the outflow, and the structure of the dissipation region are derived from first principles. These results are independent of the dissipation mechanism. It is shown that a generic feature of asymmetric reconnection is that the X-line and stagnation point are not colocated, leading to a bulk flow of plasma across the X-line. The scaling laws are verified using two-dimensional resistive magnetohydrodynamics numerical simulations for the special case of asymmetric magnetic fields with symmetric density. Observational signatures and applications to reconnection in the magnetosphere are discussed.

  10. GOOSE, a generalized object-oriented simulation environment

    SciTech Connect

    Ford, C.E.; March-Leuba, C. ); Guimaraes, L.; Ugolini, D. . Dept. of Nuclear Engineering)

    1991-01-01

    GOOSE, prototype software for a fully interactive, object-oriented simulation environment, is being developed as part of the Advanced Controls Program at Oak Ridge National Laboratory. Dynamic models may easily be constructed and tested; fully interactive capabilities allow the user to alter model parameters and complexity without recompilation. This environment provides access to powerful tools, such as numerical integration packages, graphical displays, and online help. Portability has been an important design goal; the system was written in Objective-C in order to run on a wide variety of computers and operating systems, including UNIX workstations and personal computers. A detailed library of nuclear reactor components, currently under development, will also be described. 5 refs., 4 figs.

  11. 3-D General Relativistic MHD Simulations of Generating Jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Koide, S.; Shibata, K.; Kudoh, T.; Sol, H.; Hughes, J. P.

    2001-12-01

    We have investigated the dynamics of an accretion disk around Schwarzschild black holes initially threaded by a uniform poloidal magnetic field in a non-rotating corona (either in a steady-state infalling state) around a non-rotating black hole using a 3-D GRMHD with the ``axisymmetry'' along the z-direction. Magnetic field is tightly twisted by the rotation of the disk, and plasmas in the shocked region of the disk are accelerated by J x B force to form bipolar relativistic jets. In order to investigate variabilities of generated relativistic jets and magnetic field structure inside jets, we have performed calculations using the 3-D GRMHD code with a full 3-dimensional system without the axisymmetry. We have investigated how the third dimension affects the global disk dynamics and jet generation. We will perform simulations with various incoming flows from an accompanying star.

  12. 3-D General Relativistic MHD Simulations of Generating Jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Koide, S.; Shibata, K.; Kudoh, T.; Frank, J.; Sol, H.

    1999-05-01

    Koide et al have investigated the dynamics of an accretion disk initially threaded by a uniform poloidal magnetic field in a non-rotating corona (either in a steady-state infalling state or in hydrostatic equilibrium) around a non-rotating black hole using a 3-D GRMHD with the ``axisymmetry'' along the z-direction. Magnetic field is tightly twisted by the rotation of the disk, and plasmas in the shocked region of the disk are accelerated by J x B force to form bipolar relativistic jets. In order to investigate variabilities of generated relativistic jets and magnetic field structure inside jets, we have performed calculations using the 3-D GRMHD code on a full 3-dimensional system. We will investigate how the third dimension affects the global disk dynamics. 3-D RMHD simulations wil be also performed to investigate the dynamics of a jet with a helical mangetic field in it.

  13. Jet Formation with 3-D General Relativistic MHD Simulations

    NASA Astrophysics Data System (ADS)

    Richardson, G. A.; Nishikawa, K.-I.; Preece, R.; Hardee, P.; Koide, S.; Shibata, K.; Kudoh, T.; Sol, H.; Hughes, J. P.; Fishman, J.

    2002-12-01

    We have investigated the dynamics of an accretion disk around Schwarzschild black holes initially threaded by a uniform poloidal magnetic field in a non-rotating corona (in a steady-state infalling state) around a non-rotating black hole using 3-D GRMHD with the ``axisymmetry'' along the z-direction. The magnetic field is tightly twisted by the rotation of the accretion disk, and plasmas in the shocked region of the disk are accelerated by the J x B force to form bipolar relativistic jets. In order to investigate variabilities of generated relativistic jets and the magnetic field structure inside jets, we have performed calculations using the 3-D GRMHD code with a full 3-dimensional system without the axisymmetry. We have investigated how the third dimension affects the global disk dynamics and jet generation. We will perform simulations with various incoming flows from an accompanying star.

  14. 3-D General Relativistic MHD Simulations of Generating Jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, Ken-Ichi; Koide, Shinji; Shibata, Kazunari; Kudoh, Takashiro; Sol, Helene; Hughes, John

    2002-04-01

    We have investigated the dynamics of an accretion disk around Schwarzschild black holes initially threaded by a uniform poloidal magnetic field in a non-rotating corona (either in a steady-state infalling state) around a non-rotating black hole using a 3-D GRMHD with the ``axisymmetry'' along the z-direction. Magnetic field is tightly twisted by the rotation of the disk, and plasmas in the shocked region of the disk are accelerated by J × B force to form bipolar relativistic jets. In order to investigate variabilities of generated relativistic jets and magnetic field structure inside jets, we have performed calculations using the 3-D GRMHD code with a full 3-dimensional system without the axisymmetry. We have investigated how the third dimension affects the global disk dynamics and jet generation. We will perform simulations with various incoming flows from an accompanying star.

  15. Synchronization of autonomous objects in discrete event simulation

    NASA Technical Reports Server (NTRS)

    Rogers, Ralph V.

    1990-01-01

    Autonomous objects in event-driven discrete event simulation offer the potential to combine the freedom of unrestricted movement and positional accuracy through Euclidean space of time-driven models with the computational efficiency of event-driven simulation. The principal challenge to autonomous object implementation is object synchronization. The concept of a spatial blackboard is offered as a potential methodology for synchronization. The issues facing implementation of a spatial blackboard are outlined and discussed.

  16. Parametrizing linear generalized Langevin dynamics from explicit molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Gottwald, Fabian; Karsten, Sven; Ivanov, Sergei D.; Kühn, Oliver

    2015-06-01

    Fundamental understanding of complex dynamics in many-particle systems on the atomistic level is of utmost importance. Often the systems of interest are of macroscopic size but can be partitioned into a few important degrees of freedom which are treated most accurately and others which constitute a thermal bath. Particular attention in this respect attracts the linear generalized Langevin equation, which can be rigorously derived by means of a linear projection technique. Within this framework, a complicated interaction with the bath can be reduced to a single memory kernel. This memory kernel in turn is parametrized for a particular system studied, usually by means of time-domain methods based on explicit molecular dynamics data. Here, we discuss that this task is more naturally achieved in frequency domain and develop a Fourier-based parametrization method that outperforms its time-domain analogues. Very surprisingly, the widely used rigid bond method turns out to be inappropriate in general. Importantly, we show that the rigid bond approach leads to a systematic overestimation of relaxation times, unless the system under study consists of a harmonic bath bi-linearly coupled to the relevant degrees of freedom.

  17. 2 Gbit/s 0.5 μm complementary metal-oxide semiconductor optical transceiver with event-driven dynamic power-on capability

    NASA Astrophysics Data System (ADS)

    Wang, Xingle; Kiamilev, Fouad; Gui, Ping; Wang, Xiaoqing; Ekman, Jeremy; Zuo, Yongrong; Blankenberg, Jason; Haney, Michael

    2006-06-01

    A 2 Gb/s0.5 μm complementary metal-oxide semiconductor optical transceiver designed for board- or backplane level power-efficient interconnections is presented. The transceiver supports optical wake-on-link (OWL), an event-driven dynamic power-on technique. Depending on external events, the transceiver resides in either the active mode or the sleep mode and switches accordingly. The active-to-sleep transition shuts off the normal, gigabit link and turns on dedicated circuits to establish a low-power (~1.8 mW), low data rate (less than 100 Mbits/s) link. In contrast the normal, gigabit link consumes over 100 mW. Similarly the sleep-to-active transition shuts off the low-power link and turns on the normal, gigabit link. The low-power link, sharing the same optical channel with the normal, gigabit link, is used to achieve transmitter/receiver pair power-on synchronization and greatly reduces the power consumption of the transceiver. A free-space optical platform was built to evaluate the transceiver performance. The experiment successfully demonstrated the event-driven dynamic power-on operation. To our knowledge, this is the first time a dynamic power-on scheme has been implemented for optical interconnects. The areas of the circuits that implement the low-power link are approximately one-tenth of the areas of the gigabit link circuits.

  18. General relativistic magnetohydrodynamical simulations of the jet in M 87

    NASA Astrophysics Data System (ADS)

    Mościbrodzka, Monika; Falcke, Heino; Shiokawa, Hotaka

    2016-02-01

    Context. The connection between black hole, accretion disk, and radio jet can be constrained best by fitting models to observations of nearby low-luminosity galactic nuclei, in particular the well-studied sources Sgr A* and M 87. There has been considerable progress in modeling the central engine of active galactic nuclei by an accreting supermassive black hole coupled to a relativistic plasma jet. However, can a single model be applied to a range of black hole masses and accretion rates? Aims: Here we want to compare the latest three-dimensional numerical model, originally developed for Sgr A* in the center of the Milky Way, to radio observations of the much more powerful and more massive black hole in M 87. Methods: We postprocess three-dimensional GRMHD models of a jet-producing radiatively inefficient accretion flow around a spinning black hole using relativistic radiative transfer and ray-tracing to produce model spectra and images. As a key new ingredient in these models, we allow the proton-electron coupling in these simulations depend on the magnetic properties of the plasma. Results: We find that the radio emission in M 87 is described well by a combination of a two-temperature accretion flow and a hot single-temperature jet. Most of the radio emission in our simulations comes from the jet sheath. The model fits the basic observed characteristics of the M 87 radio core: it is "edge-brightened", starts subluminally, has a flat spectrum, and increases in size with wavelength. The best fit model has a mass-accretion rate of Ṁ ~ 9 × 10-3M⊙ yr-1 and a total jet power of Pj ~ 1043 erg s-1. Emission at λ = 1.3 mm is produced by the counter-jet close to the event horizon. Its characteristic crescent shape surrounding the black hole shadow could be resolved by future millimeter-wave VLBI experiments. Conclusions: The model was successfully derived from one for the supermassive black hole in the center of the Milky Way by appropriately scaling mass and

  19. Simulating extreme-mass-ratio systems in full general relativity

    NASA Astrophysics Data System (ADS)

    East, William E.; Pretorius, Frans

    2013-05-01

    We introduce a new method for numerically evolving the full Einstein field equations in situations where the spacetime is dominated by a known background solution. The technique leverages the knowledge of the background solution to subtract off its contribution to the truncation error, thereby more efficiently achieving a desired level of accuracy. We demonstrate the method by applying it to the radial infall of a solar-type star into supermassive black holes with mass ratios ≥106. The self-gravity of the star is thus consistently modeled within the context of general relativity, and the star’s interaction with the black hole computed with moderate computational cost, despite the over five orders of magnitude difference in gravitational potential (as defined by the ratio of mass to radius). We compute the tidal deformation of the star during infall, and the gravitational wave emission, finding the latter is close to the prediction of the point-particle limit.

  20. An intelligent interactive simulator of clinical reasoning in general surgery.

    PubMed Central

    Wang, S.; el Ayeb, B.; Echavé, V.; Preiss, B.

    1993-01-01

    We introduce an interactive computer environment for teaching in general surgery and for diagnostic assistance. The environment consists of a knowledge-based system coupled with an intelligent interface that allows users to acquire conceptual knowledge and clinical reasoning techniques. Knowledge is represented internally within a probabilistic framework and externally through a interface inspired by Concept Graphics. Given a set of symptoms, the internal knowledge framework computes the most probable set of diseases as well as best alternatives. The interface displays CGs illustrating the results and prompting essential facts of a medical situation or a process. The system is then ready to receive additional information or to suggest further investigation. Based on the new information, the system will narrow the solutions with increased belief coefficients. PMID:8130508

  1. An intelligent interactive simulator of clinical reasoning in general surgery.

    PubMed

    Wang, S; el Ayeb, B; Echavé, V; Preiss, B

    1993-01-01

    We introduce an interactive computer environment for teaching in general surgery and for diagnostic assistance. The environment consists of a knowledge-based system coupled with an intelligent interface that allows users to acquire conceptual knowledge and clinical reasoning techniques. Knowledge is represented internally within a probabilistic framework and externally through a interface inspired by Concept Graphics. Given a set of symptoms, the internal knowledge framework computes the most probable set of diseases as well as best alternatives. The interface displays CGs illustrating the results and prompting essential facts of a medical situation or a process. The system is then ready to receive additional information or to suggest further investigation. Based on the new information, the system will narrow the solutions with increased belief coefficients.

  2. Plasma Jet Simulations Using a Generalized Ohm's Law

    NASA Astrophysics Data System (ADS)

    Ebersohn, F.; Shebalin, J. V.; Girimaji, S. S.

    2012-12-01

    Plasma jets are important physical phenomena in astrophysics and plasma propulsion devices. A currently proposed dual jet plasma propulsion device to be used for ISS experiments strongly resembles a coronal loop and further draws a parallel between these physical systems [1]. To study plasma jets we use numerical methods which solve the compressible MHD equations using the generalized Ohm's law[2]. Herein we discuss the crucial underlying physics of these systems along with the numerical procedures we utilize to study them. Recent results from our numerical experiments will be presented and discussed. [1] T. Glover, et al., The VASIMR® VF-200-1 ISS Experiment as a Laboratory for Astrophysics, Poster SM51C-1831, AGU Fall Meeting, San Francisco, December 13-17, 2010. [2] F. Ebersohn, J. V Shebalin, S. Girimaji and D. Staack, Magnetic Field Effects on Plasma Plumes, Paper O2-404, 39th EPS Conference on Plasma Physics, Stockholm, July 2-6, 2012.;

  3. A generalized framework for interactive dynamic simulation for MultiRigid bodies.

    PubMed

    Son, Wookho; Kim, Kyunghwan; Amato, Nancy M; Trinkle, Jeffrey C

    2004-04-01

    This paper presents a generalized framework for dynamic simulation realized in a prototype simulator called the Interactive Generalized Motion Simulator (I-GMS), which can simulate motions of multirigid-body systems with contact interaction in virtual environments. I-GMS is designed to meet two important goals: generality and interactivity. By generality, we mean a dynamic simulator which can easily support various systems of rigid bodies, ranging from a single free-flying rigid object to complex linkages such as those needed for robotic systems or human body simulation. To provide this generality, we have developed I-GMS in an object-oriented framework. The user interactivity is supported through a haptic interface for articulated bodies, introducing interactive dynamic simulation schemes. This user-interaction is achieved by performing push and pull operations via the PHANToM haptic device, which runs as an integrated part of I-GMS. Also, a hybrid scheme was used for simulating internal contacts (between bodies in the multirigid-body system) in the presence of friction, which could avoid the nonexistent solution problem often faced when solving contact problems with Coulomb friction. In our hybrid scheme, two impulse-based methods are exploited so that different methods are applied adaptively, depending on whether the current contact situation is characterized as "bouncing" or "steady." We demonstrate the user-interaction capability of I-GMS through on-line editing of trajectories of a 6-degree of freedom (dof) articulated structure.

  4. No Vent Tank Fill and Transfer Line Chilldown Analysis by Generalized Fluid System Simulation Program (GFSSP)

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok

    2013-01-01

    The purpose of the paper is to present the analytical capability developed to model no vent chill and fill of cryogenic tank to support CPST (Cryogenic Propellant Storage and Transfer) program. Generalized Fluid System Simulation Program (GFSSP) was adapted to simulate charge-holdvent method of Tank Chilldown. GFSSP models were developed to simulate chilldown of LH2 tank in K-site Test Facility and numerical predictions were compared with test data. The report also describes the modeling technique of simulating the chilldown of a cryogenic transfer line and GFSSP models were developed to simulate the chilldown of a long transfer line and compared with test data.

  5. Relationship Between Simulated Gap Wear and Generalized Wear of Resin Luting Cements.

    PubMed

    Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miayazaki, M

    The relationship between the simulated gap wear and generalized wear of resin luting cements was investigated. Five resin luting cements, G-Cem LinkForce (GL), Multilink Automix (MA), NX3 Nexus, Panavia V5 (PV), and RelyX Ultimate were evaluated and subsequently subjected to a wear challenge in a Leinfelder-Suzuki (Alabama) wear simulation device. Half of the specimens from each resin luting cement were photo-cured for 40 seconds and the other half were not photo-cured. The simulated gap and generalized wear were generated using a flat-ended stainless steel antagonist. Wear testing was performed in a water slurry of polymethyl methacrylate beads, and the simulated gap and generalized wear were determined using a noncontact profilometer (Proscan 2100) in conjunction with the Proscan and AnSur 3D software. A strong relationship was found between the gap wear and generalized wear simulation models. The simulated gap wear and generalized wear of the resin luting cements followed similar trends in terms of both volume loss and mean depth of wear facets with each curing method. Unlike the simulated gap wear and generalized wear of GL and PV, those of MA, NX, and RU were influenced by the curing method. The results of this study indicate that simulated gap wear of resin luting cements is very similar to simulated generalized wear. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing method.

  6. Instructor and student pilots' subjective evaluation of a general aviation simulator with a terrain visual system

    NASA Technical Reports Server (NTRS)

    Kiteley, G. W.; Harris, R. L., Sr.

    1978-01-01

    Ten student pilots were given a 1 hour training session in the NASA Langley Research Center's General Aviation Simulator by a certified flight instructor and a follow-up flight evaluation was performed by the student's own flight instructor, who has also flown the simulator. The students and instructors generally felt that the simulator session had a positive effect on the students. They recommended that a simulator with a visual scene and a motion base would be useful in performing such maneuvers as: landing approaches, level flight, climbs, dives, turns, instrument work, and radio navigation, recommending that the simulator would be an efficient means of introducing the student to new maneuvers before doing them in flight. The students and instructors estimated that about 8 hours of simulator time could be profitably devoted to the private pilot training.

  7. A General Simulator Using State Estimation for a Space Tug Navigation System. [computerized simulation, orbital position estimation and flight mechanics

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1975-01-01

    A general simulation program is presented (GSP) involving nonlinear state estimation for space vehicle flight navigation systems. A complete explanation of the iterative guidance mode guidance law, derivation of the dynamics, coordinate frames, and state estimation routines are given so as to fully clarify the assumptions and approximations involved so that simulation results can be placed in their proper perspective. A complete set of computer acronyms and their definitions as well as explanations of the subroutines used in the GSP simulator are included. To facilitate input/output, a complete set of compatable numbers, with units, are included to aid in data development. Format specifications, output data phrase meanings and purposes, and computer card data input are clearly spelled out. A large number of simulation and analytical studies were used to determine the validity of the simulator itself as well as various data runs.

  8. General specifications for the development of a PC-based simulator of the NASA RECON system

    NASA Technical Reports Server (NTRS)

    Dominick, Wayne D. (Editor); Triantafyllopoulos, Spiros

    1984-01-01

    The general specifications for the design and implementation of an IBM PC/XT-based simulator of the NASA RECON system, including record designs, file structure designs, command language analysis, program design issues, error recovery considerations, and usage monitoring facilities are discussed. Once implemented, such a simulator will be utilized to evaluate the effectiveness of simulated information system access in addition to actual system usage as part of the total educational programs being developed within the NASA contract.

  9. Event-Driven Collaboration through Publish/Subscribe Messaging Services for Near-Real- Time Environmental Sensor Anomaly Detection and Management

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Downey, S.; Minsker, B.; Myers, J. D.; Wentling, T.; Marini, L.

    2006-12-01

    One of the challenges in designing cyberinfrastructure for national environmental observatories is how to provide integrated cyberenvironment which not only provides a standardized pipeline for streaming data from sensors into the observatory for archiving and distribution, but also makes raw data and identified events available in real-time for use in individual and group research efforts. This aspect of observatories is critical for promoting efficient collaboration and innovation among scientists and engineers and enabling observatories to serve as a focus that directly supports the broad community. The National Center for Supercomputing Applications' Environmental Cyberinfrastructure Demo (ECID) project has adopted an event-driven architecture and developed a CyberCollaboratory to facilitate event-driven, near-real-time collaboration and management of sensors and workflows for bringing data from environmental observatories into local research contexts. The CyberCollaboratory's event broker uses publish-subscribe service powered by JMS (Java Messaging Service) with semantics-enhanced messages using RDF (Resource Description Framework) triples to allow exchange of contextual information about the event between the event generators and the event consumers. Non-scheduled, event-driven collaboration effectively reduces the barrier to collaboration for scientists and engineers and promotes much faster turn-around time for critical environmental events. This is especially useful for real-time adaptive monitoring and modeling of sensor data in environmental observatories. In this presentation, we illustrate our system using a sensor anomaly detection event as an example where near-real- time data streams from field sensor in Corpus Christi Bay, Texas, trigger monitoring/anomaly alerts in the CyberCollaboratory's CyberDashboard and collaborative activities in the CyberCollaboratory. The CyberDashboard is a Java application where users can monitor various events

  10. A brief history of the introduction of generalized ensembles to Markov chain Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Berg, Bernd A.

    2017-03-01

    The most efficient weights for Markov chain Monte Carlo calculations of physical observables are not necessarily those of the canonical ensemble. Generalized ensembles, which do not exist in nature but can be simulated on computers, lead often to a much faster convergence. In particular, they have been used for simulations of first order phase transitions and for simulations of complex systems in which conflicting constraints lead to a rugged free energy landscape. Starting off with the Metropolis algorithm and Hastings' extension, I present a minireview which focuses on the explosive use of generalized ensembles in the early 1990s. Illustrations are given, which range from spin models to peptides.

  11. General purpose simulation system of the data management system for space shuttle mission 18

    NASA Technical Reports Server (NTRS)

    Bengtson, N. M.; Mellichamp, J. M.; Crenshaw, J.

    1975-01-01

    The simulation program of the science and engineering data management system for the space shuttle is presented. The programming language used was General Purpose Simulation System V (OS). The data flow was modeled from its origin at the experiments or subsystems to transmission from the space shuttle. Mission 18 was the particular flight chosen for simulation. First, the general structure of the program is presented and the trade studies which were performed are identified. Inputs required to make runs are discussed followed by identification of the output statistics. Some areas for model modifications are pointed out. A detailed model configuration, program listing and results are included.

  12. A possible mechanism for pressure reversal of general anaesthetics from molecular simulations

    NASA Astrophysics Data System (ADS)

    Chau, P.-L.; Hoang, Paul N. M.; Picaud, Sylvain; Jedlovszky, Pál

    2007-04-01

    The effect of general anaesthetics is pressure-dependent. We have simulated a fully hydrated dimyristoylphosphatidylcholine bilayer with halothane (a general anaesthetic) embedded, at pressures of 1, 200 and 400 atm, respectively. We find that at higher pressures, halothane molecules tend to cluster together. Based on these results, we propose a possible mechanisms for pressure reversal of anaesthesia.

  13. A general CellML simulation code generator using ODE solving scheme description.

    PubMed

    Amano, Akira; Soejima, Naoki; Shimayoshi, Takao; Kuwabara, Hiroaki; Kunieda, Yoshitoshi

    2011-01-01

    To cope with the complexity of the biological function simulation models, model representation with description language is becoming popular. However, simulation software itself becomes complex in these environment, thus, it is difficult to modify target computation resources or numerical calculation methods or simulation conditions. Typical biological function simulation software consists of 1) model equation, 2) boundary conditions and 3) ODE solving scheme. Introducing the description model file such as CellML is useful for generalizing the first point and partly second point, however, third point is difficult to handle. We introduce a simulation software generation system which use markup language based description of ODE solving scheme together with cell model description file. By using this software, we can easily generate biological simulation program code with different ODE solving schemes. To show the efficiency of our system, experimental results of several simulation models with different ODE scheme and different computation resources are shown.

  14. Generalized image charge solvation model for electrostatic interactions in molecular dynamics simulations of aqueous solutions

    NASA Astrophysics Data System (ADS)

    Deng, Shaozhong; Xue, Changfeng; Baumketner, Andriy; Jacobs, Donald; Cai, Wei

    2013-07-01

    This paper extends the image charge solvation model (ICSM) [Y. Lin, A. Baumketner, S. Deng, Z. Xu, D. Jacobs, W. Cai, An image-based reaction field method for electrostatic interactions in molecular dynamics simulations of aqueous solutions, J. Chem. Phys. 131 (2009) 154103], a hybrid explicit/implicit method to treat electrostatic interactions in computer simulations of biomolecules formulated for spherical cavities, to prolate spheroidal and triaxial ellipsoidal cavities, designed to better accommodate non-spherical solutes in molecular dynamics (MD) simulations. In addition to the utilization of a general truncated octahedron as the MD simulation box, central to the proposed extension is an image approximation method to compute the reaction field for a point charge placed inside such a non-spherical cavity by using a single image charge located outside the cavity. The resulting generalized image charge solvation model (GICSM) is tested in simulations of liquid water, and the results are analyzed in comparison with those obtained from the ICSM simulations as a reference. We find that, for improved computational efficiency due to smaller simulation cells and consequently a less number of explicit solvent molecules, the generalized model can still faithfully reproduce known static and dynamic properties of liquid water at least for systems considered in the present paper, indicating its great potential to become an accurate but more efficient alternative to the ICSM when bio-macromolecules of irregular shapes are to be simulated.

  15. Generalized Langevin dynamics simulation: numerical integration and application of the generalized Langevin equation with an exponential model for the friction kernel

    NASA Astrophysics Data System (ADS)

    Wan, Shun Zhou; Wang, Cun Xin; Shi, Yun Yu

    An efficient procedure is introduced for a generalized Langevin dynamics simulation when the exponential model is taken for the friction kernel. The leap frog algorithm is used for numerical integration of the generalized Langevin equation. Simulation with this model has been performed on a cyclic undecapeptide, cyclosporin A (CPA). By comparison with the results obtained from previous simulations, the method proves to be reliable and efficient in the simulation of CPA.

  16. Simulation of the great plains low-level jet and associated clouds by general circulation models

    SciTech Connect

    Ghan, S.J.; Bian, X.; Corsetti, L.

    1996-07-01

    The low-level jet frequently observed in the Great Plains of the United States forms preferentially at night and apparently influences the timing of the thunderstorms in the region. The authors have found that both the European Centre for Medium-Range Weather Forecasts general circulation model and the National Center for Atmospheric Research Community Climate Model simulate the low-level jet rather well, although the spatial distribution of the jet frequency simulated by the two GCM`s differ considerably. Sensitivity experiments have demonstrated that the simulated low-level jet is surprisingly robust, with similar simulations at much coarser horizontal and vertical resolutions. However, both GCM`s fail to simulate the observed relationship between clouds and the low-level jet. The pronounced nocturnal maximum in thunderstorm frequency associated with the low-level jet is not simulated well by either GCM, with only weak evidence of a nocturnal maximum in the Great Plains. 36 refs., 20 figs.

  17. A Multi-mission Event-Driven Component-Based System for Support of Flight Software Development, ATLO, and Operations first used by the Mars Science Laboratory (MSL) Project

    NASA Technical Reports Server (NTRS)

    Dehghani, Navid; Tankenson, Michael

    2006-01-01

    This paper details an architectural description of the Mission Data Processing and Control System (MPCS), an event-driven, multi-mission ground data processing components providing uplink, downlink, and data management capabilities which will support the Mars Science Laboratory (MSL) project as its first target mission. MPCS is developed based on a set of small reusable components, implemented in Java, each designed with a specific function and well-defined interfaces. An industry standard messaging bus is used to transfer information among system components. Components generate standard messages which are used to capture system information, as well as triggers to support the event-driven architecture of the system. Event-driven systems are highly desirable for processing high-rate telemetry (science and engineering) data, and for supporting automation for many mission operations processes.

  18. A Multi-mission Event-Driven Component-Based System for Support of Flight Software Development, ATLO, and Operations first used by the Mars Science Laboratory (MSL) Project

    NASA Technical Reports Server (NTRS)

    Dehghani, Navid; Tankenson, Michael

    2006-01-01

    This paper details an architectural description of the Mission Data Processing and Control System (MPCS), an event-driven, multi-mission ground data processing components providing uplink, downlink, and data management capabilities which will support the Mars Science Laboratory (MSL) project as its first target mission. MPCS is developed based on a set of small reusable components, implemented in Java, each designed with a specific function and well-defined interfaces. An industry standard messaging bus is used to transfer information among system components. Components generate standard messages which are used to capture system information, as well as triggers to support the event-driven architecture of the system. Event-driven systems are highly desirable for processing high-rate telemetry (science and engineering) data, and for supporting automation for many mission operations processes.

  19. The Generalized Onsager Model and DSMC Simulations of High-Speed Rotating Flow with Swirling Feed

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev

    2017-01-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer at the end-caps in a high-speed rotating cylinder, are extended to incorporate the angular momentum of the feed gas for a swirling feed for single component gas and binary gas mixture. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. The equations are restricted to the limit of high Reynolds number and (length/radius) ratio, but there is no limitation on the stratification parameter. The linear operators in the generalized Onsager and generalized Carrier-Maslen equations with swirling feed are still self-adjoint, and so the eigenfunctions form a complete orthogonal basis set. The analytical solutions are compared with direct simulation Monte Carlo (DSMC) simulations. The comparison reveals that the boundary conditions in the simulations and analysis have to be matched with care. When these precautions are taken, there is excellent agreement between analysis and simulations, to within 15%.

  20. The Generalized Onsager Model and DSMC Simulations of High-Speed Rotating Flow with Swirling Feed

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev

    2016-09-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer at the end-caps in a high-speed rotating cylinder, are extended to incorporate the angular momentum of the feed gas for a swirling feed for single component gas and binary gas mixture. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. The equations are restricted to the limit of high Reynolds number and (length/radius) ratio, but there is no limitation on the stratification parameter. The linear operators in the generalized Onsager and generalized Carrier-Maslen equations with swirling feed are still self-adjoint, and so the eigenfunctions form a complete orthogonal basis set. The analytical solutions are compared with direct simulation Monte Carlo (DSMC) simulations. The comparison reveals that the boundary conditions in the simulations and analysis have to be matched with care. When these precautions are taken, there is excellent agreement between analysis and simulations, to within 15%.

  1. The Generalized Onsager Model and DSMC Simulations of High-Speed Rotating Flow with Swirling Feed

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2016-11-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer at the end-caps in a high-speed rotating cylinder, are extended to incorporate the angular momentum of the feed gas for a swirling feed for single component gas and binary gas mixture. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. The equations are restricted to the limit of high Reynolds number and (length/radius) ratio, but there is no limitation on the stratification parameter. The linear operators in the generalized Onsager and generalized Carrier-Maslen equations with swirling feed are still self-adjoint, and so the eigenfunctions form a complete orthogonal basis set. The analytical solutions are compared with direct simulation Monte Carlo (DSMC) simulations. The comparison reveals that the boundary conditions in the simulations and analysis have to be matched with care. When these precautions are taken, there is excellent agreement between analysis and simulations, to within 15%.

  2. A general CFD framework for fault-resilient simulations based on multi-resolution information fusion

    NASA Astrophysics Data System (ADS)

    Lee, Seungjoon; Kevrekidis, Ioannis G.; Karniadakis, George Em

    2017-10-01

    We develop a general CFD framework for multi-resolution simulations to target multiscale problems but also resilience in exascale simulations, where faulty processors may lead to gappy, in space-time, simulated fields. We combine approximation theory and domain decomposition together with statistical learning techniques, e.g. coKriging, to estimate boundary conditions and minimize communications by performing independent parallel runs. To demonstrate this new simulation approach, we consider two benchmark problems. First, we solve the heat equation (a) on a small number of spatial ;patches; distributed across the domain, simulated by finite differences at fine resolution and (b) on the entire domain simulated at very low resolution, thus fusing multi-resolution models to obtain the final answer. Second, we simulate the flow in a lid-driven cavity in an analogous fashion, by fusing finite difference solutions obtained with fine and low resolution assuming gappy data sets. We investigate the influence of various parameters for this framework, including the correlation kernel, the size of a buffer employed in estimating boundary conditions, the coarseness of the resolution of auxiliary data, and the communication frequency across different patches in fusing the information at different resolution levels. In addition to its robustness and resilience, the new framework can be employed to generalize previous multiscale approaches involving heterogeneous discretizations or even fundamentally different flow descriptions, e.g. in continuum-atomistic simulations.

  3. General Relativistic Radiative Transfer and GeneralRelativistic MHD Simulations of Accretion and Outflows of Black Holes

    SciTech Connect

    Fuerst, Steven V.; Mizuno, Yosuke; Nishikawa, Ken-Ichi; Wu, Kinwah; /Mullard Space Sci. Lab.

    2007-01-05

    We calculate the emission from relativistic flows in black hole systems using a fully general relativistic radiative transfer formulation, with flow structures obtained by general relativistic magneto-hydrodynamic simulations. We consider thermal free-free emission and thermal synchrotron emission. Bright filament-like features protrude (visually) from the accretion disk surface, which are enhancements of synchrotron emission where the magnetic field roughly aligns with the line-of-sight in the co-moving frame. The features move back and forth as the accretion flow evolves, but their visibility and morphology are robust. We propose that variations and drifts of the features produce certain X-ray quasi-periodic oscillations (QPOs) observed in black-hole X-ray binaries.

  4. General purpose simulation system of the data management system for Space Shuttle mission 18

    NASA Technical Reports Server (NTRS)

    Bengtson, N. M.; Mellichamp, J. M.; Smith, O. C.

    1976-01-01

    A simulation program for the flow of data through the Data Management System of Spacelab and Space Shuttle was presented. The science, engineering, command and guidance, navigation and control data were included. The programming language used was General Purpose Simulation System V (OS). The science and engineering data flow was modeled from its origin at the experiments and subsystems to transmission from Space Shuttle. Command data flow was modeled from the point of reception onboard and from the CDMS Control Panel to the experiments and subsystems. The GN&C data flow model handled data between the General Purpose Computer and the experiments and subsystems. Mission 18 was the particular flight chosen for simulation. The general structure of the program is presented, followed by a user's manual. Input data required to make runs are discussed followed by identification of the output statistics. The appendices contain a detailed model configuration, program listing and results.

  5. Generalized Metropolis dynamics with a generalized master equation: an approach for time-independent and time-dependent Monte Carlo simulations of generalized spin systems.

    PubMed

    da Silva, Roberto; Drugowich de Felício, José Roberto; Martinez, Alexandre Souto

    2012-06-01

    The extension of Boltzmann-Gibbs thermostatistics, proposed by Tsallis, introduces an additional parameter q to the inverse temperature β. Here, we show that a previously introduced generalized Metropolis dynamics to evolve spin models is not local and does not obey the detailed energy balance. In this dynamics, locality is only retrieved for q=1, which corresponds to the standard Metropolis algorithm. Nonlocality implies very time-consuming computer calculations, since the energy of the whole system must be reevaluated when a single spin is flipped. To circumvent this costly calculation, we propose a generalized master equation, which gives rise to a local generalized Metropolis dynamics that obeys the detailed energy balance. To compare the different critical values obtained with other generalized dynamics, we perform Monte Carlo simulations in equilibrium for the Ising model. By using short-time nonequilibrium numerical simulations, we also calculate for this model the critical temperature and the static and dynamical critical exponents as functions of q. Even for q≠1, we show that suitable time-evolving power laws can be found for each initial condition. Our numerical experiments corroborate the literature results when we use nonlocal dynamics, showing that short-time parameter determination works also in this case. However, the dynamics governed by the new master equation leads to different results for critical temperatures and also the critical exponents affecting universality classes. We further propose a simple algorithm to optimize modeling the time evolution with a power law, considering in a log-log plot two successive refinements.

  6. Experiments in monthly mean simulation of the atmosphere with a coarse-mesh general circulation model

    NASA Technical Reports Server (NTRS)

    Lutz, R. J.; Spar, J.

    1978-01-01

    The Hansen atmospheric model was used to compute five monthly forecasts (October 1976 through February 1977). The comparison is based on an energetics analysis, meridional and vertical profiles, error statistics, and prognostic and observed mean maps. The monthly mean model simulations suffer from several defects. There is, in general, no skill in the simulation of the monthly mean sea-level pressure field, and only marginal skill is indicated for the 850 mb temperatures and 500 mb heights. The coarse-mesh model appears to generate a less satisfactory monthly mean simulation than the finer mesh GISS model.

  7. General circulation model simulations of winter and summer sea-level pressures over North America

    USGS Publications Warehouse

    McCabe, G.J.; Legates, D.R.

    1992-01-01

    In this paper, observed sea-level pressures were used to evaluate winter and summer sea-level pressures over North America simulated by the Goddard Institute for Space Studies (GISS) and the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation models. The objective of the study is to determine how similar the spatial and temporal distributions of GCM-simulated daily sea-level pressures over North America are to observed distributions. Overall, both models are better at reproducing observed within-season variance of winter and summer sea-level pressures than they are at simulating the magnitude of mean winter and summer sea-level pressures. -from Authors

  8. Development and evaluation of a general aviation real world noise simulator

    NASA Technical Reports Server (NTRS)

    Galanter, E.; Popper, R.

    1980-01-01

    An acoustic playback system is described which realistically simulates the sounds experienced by the pilot of a general aviation aircraft during engine idle, take-off, climb, cruise, descent, and landing. The physical parameters of the signal as they appear in the simulator environment are compared to analogous parameters derived from signals recorded during actual flight operations. The acoustic parameters of the simulated and real signals during cruise conditions are within plus or minus two dB in third octave bands from 0.04 to 4 kHz. The overall A-weighted levels of the signals are within one dB of signals generated in the actual aircraft during equivalent maneuvers. Psychoacoustic evaluations of the simulator signal are compared with similar measurements based on transcriptions of actual aircraft signals. The subjective judgments made by human observers support the conclusion that the simulated sound closely approximates transcribed sounds of real aircraft.

  9. The General-Use Nodal Network Solver (GUNNS) Modeling Package for Space Vehicle Flow System Simulation

    NASA Technical Reports Server (NTRS)

    Harvey, Jason; Moore, Michael

    2013-01-01

    The General-Use Nodal Network Solver (GUNNS) is a modeling software package that combines nodal analysis and the hydraulic-electric analogy to simulate fluid, electrical, and thermal flow systems. GUNNS is developed by L-3 Communications under the TS21 (Training Systems for the 21st Century) project for NASA Johnson Space Center (JSC), primarily for use in space vehicle training simulators at JSC. It has sufficient compactness and fidelity to model the fluid, electrical, and thermal aspects of space vehicles in real-time simulations running on commodity workstations, for vehicle crew and flight controller training. It has a reusable and flexible component and system design, and a Graphical User Interface (GUI), providing capability for rapid GUI-based simulator development, ease of maintenance, and associated cost savings. GUNNS is optimized for NASA's Trick simulation environment, but can be run independently of Trick.

  10. skelesim: an extensible, general framework for population genetic simulation in R.

    PubMed

    Parobek, Christian M; Archer, Frederick I; DePrenger-Levin, Michelle E; Hoban, Sean M; Liggins, Libby; Strand, Allan E

    2017-01-01

    Simulations are a key tool in molecular ecology for inference and forecasting, as well as for evaluating new methods. Due to growing computational power and a diversity of software with different capabilities, simulations are becoming increasingly powerful and useful. However, the widespread use of simulations by geneticists and ecologists is hindered by difficulties in understanding these softwares' complex capabilities, composing code and input files, a daunting bioinformatics barrier and a steep conceptual learning curve. skelesim (an R package) guides users in choosing appropriate simulations, setting parameters, calculating genetic summary statistics and organizing data output, in a reproducible pipeline within the R environment. skelesim is designed to be an extensible framework that can 'wrap' around any simulation software (inside or outside the R environment) and be extended to calculate and graph any genetic summary statistics. Currently, skelesim implements coalescent and forward-time models available in the fastsimcoal2 and rmetasim simulation engines to produce null distributions for multiple population genetic statistics and marker types, under a variety of demographic conditions. skelesim is intended to make simulations easier while still allowing full model complexity to ensure that simulations play a fundamental role in molecular ecology investigations. skelesim can also serve as a teaching tool: demonstrating the outcomes of stochastic population genetic processes; teaching general concepts of simulations; and providing an introduction to the R environment with a user-friendly graphical user interface (using shiny). © 2016 John Wiley & Sons Ltd.

  11. Great Lakes Simulation Studies. Volume I. NETSIM: A General Network Simulator.

    DTIC Science & Technology

    1972-11-01

    L-. PIZ QUZ a M..~e 3Mpa4 L model that requires ic!65 6L .rage mpe and tha. gw.d±)i,i ce cdxecuted more rapidly. Flex1i~ ir ) _t6 a.&j terdetz~d ry tn...itsteit is cc:mp~sEd ir two sub-phases: kl) the EDB phase and (2) the Event LOG phase, The sub-phase Strictu.re or the second (simulation)I phase is...EVENT LOG, sub-phase can be cunducted. Ire ekpaecd tL.arsit ime r1.nctions are utilized during the EVENT LOu, phaae CL d)ndamicaiiy . cns~der the

  12. Generalized source method in curvilinear coordinates for 2D grating diffraction simulation

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexey A.; Tishchenko, Alexandre V.

    2017-01-01

    The article presents a curvilinear coordinate Fourier space integral method for linear optical rigorous grating diffraction simulation in 3D (crossed grating diffraction). The presented formulation extends our previous work on a related method for 1D periodic grating diffraction. Following this previous work we exploit a concept of the generalized metric sources to efficiently solve the Maxwell's equations. The article provides a general description of the method together with a detailed formulation and analysis of sinusoidal corrugation crossed grating diffraction.

  13. Generalized Canonical Correlation Analysis of Matrices with Missing Rows: A Simulation Study

    ERIC Educational Resources Information Center

    van de Velden, Michel; Bijmolt, Tammo H. A.

    2006-01-01

    A method is presented for generalized canonical correlation analysis of two or more matrices with missing rows. The method is a combination of Carroll's (1968) method and the missing data approach of the OVERALS technique (Van der Burg, 1988). In a simulation study we assess the performance of the method and compare it to an existing procedure…

  14. Estimating plant available water for general crop simulations in ALMANAC/APEX/EPIC/SWAT

    USDA-ARS?s Scientific Manuscript database

    Process-based simulation models ALMANAC/APEX/EPIC/SWAT contain generalized plant growth subroutines to predict biomass and crop yield. Environmental constraints typically restrict plant growth and yield. Water stress is often an important limiting factor; it is calculated as the sum of water use f...

  15. Computer considerations for real time simulation of a generalized rotor model

    NASA Technical Reports Server (NTRS)

    Howe, R. M.; Fogarty, L. E.

    1977-01-01

    Scaled equations were developed to meet requirements for real time computer simulation of the rotor system research aircraft. These equations form the basis for consideration of both digital and hybrid mechanization for real time simulation. For all digital simulation estimates of the required speed in terms of equivalent operations per second are developed based on the complexity of the equations and the required intergration frame rates. For both conventional hybrid simulation and hybrid simulation using time-shared analog elements the amount of required equipment is estimated along with a consideration of the dynamic errors. Conventional hybrid mechanization using analog simulation of those rotor equations which involve rotor-spin frequencies (this consititutes the bulk of the equations) requires too much analog equipment. Hybrid simulation using time-sharing techniques for the analog elements appears possible with a reasonable amount of analog equipment. All-digital simulation with affordable general-purpose computers is not possible because of speed limitations, but specially configured digital computers do have the required speed and consitute the recommended approach.

  16. Energetics analysis of the observed and simulated general circulation using three-dimensional normal mode expansions

    NASA Technical Reports Server (NTRS)

    Tanaka, Hiroshi; Kung, Ernest C.; Baker, Wayman E.

    1986-01-01

    The energetics characteristics of the observed and simulated general circulation are analyzed using three-dimensional normal mode expansions. The data sets involved are the Goddard Laboratory for Atmospheres (GLA) analysis and simulation data and the Geophysical Fluid Dynamics Laboratory (GFDL) analysis data. The spectral energy properties of the Rossby and gravity modes and energy transformations are presented. Significant influences of model characteristics and the assimilation techniques are observed in the barotropic energy spectrum, particularly for the gravity mode. Energy transformations of the zonal mean field in the GLA analysis and simulation are similar, but distinctly different from that in the GFDL analysis. However, overall, the energy generation in the baroclinic mode is largely balanced by the sink in the barotropic mode. The present study may demonstrate utilities of the three-dimensional normal mode energetics in the analysis of the general circulation.

  17. Surface air temperature simulations by AMIP general circulation models: Volcanic and ENSO signals and systematic errors

    SciTech Connect

    Mao, J.; Robock, A.

    1998-07-01

    Thirty surface air temperature simulations for 1979--88 by 29 atmospheric general circulation models are analyzed and compared with the observations over land. These models were run as part of the Atmospheric Model Intercomparison Project (AMIP). Several simulations showed serious systematic errors, up to 4--5 C, in globally averaged land air temperature. The 16 best simulations gave rather realistic reproductions of the mean climate and seasonal cycle of global land air temperature, with an average error of {minus}0.9 C for the 10-yr period. The general coldness of the model simulations is consistent with previous intercomparison studies. The regional systematic errors showed very large cold biases in areas with topography and permanent ice, which implies a common deficiency in the representation of snow-ice albedo in the diverse models. The SST and sea ice specification of climatology rather than observations at high latitudes for the first three years (1979--81) caused a noticeable drift in the neighboring land air temperature simulations, compared to the rest of the years (1982--88). Unsuccessful simulation of the extreme warm (1981) and cold (1984--85) periods implies that some variations are chaotic or unpredictable, produced by internal atmospheric dynamics and not forced by global SST patterns.

  18. Semi-analytical solution for the generalized absorbing boundary condition in molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Lee, Chung-Shuo; Chen, Yan-Yu; Yu, Chi-Hua; Hsu, Yu-Chuan; Chen, Chuin-Shan

    2017-02-01

    We present a semi-analytical solution of a time-history kernel for the generalized absorbing boundary condition in molecular dynamics (MD) simulations. To facilitate the kernel derivation, the concept of virtual atoms in real space that can conform with an arbitrary boundary in an arbitrary lattice is adopted. The generalized Langevin equation is regularized using eigenvalue decomposition and, consequently, an analytical expression of an inverse Laplace transform is obtained. With construction of dynamical matrices in the virtual domain, a semi-analytical form of the time-history kernel functions for an arbitrary boundary in an arbitrary lattice can be found. The time-history kernel functions for different crystal lattices are derived to show the generality of the proposed method. Non-equilibrium MD simulations in a triangular lattice with and without the absorbing boundary condition are conducted to demonstrate the validity of the solution.

  19. Semi-analytical solution for the generalized absorbing boundary condition in molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Lee, Chung-Shuo; Chen, Yan-Yu; Yu, Chi-Hua; Hsu, Yu-Chuan; Chen, Chuin-Shan

    2017-07-01

    We present a semi-analytical solution of a time-history kernel for the generalized absorbing boundary condition in molecular dynamics (MD) simulations. To facilitate the kernel derivation, the concept of virtual atoms in real space that can conform with an arbitrary boundary in an arbitrary lattice is adopted. The generalized Langevin equation is regularized using eigenvalue decomposition and, consequently, an analytical expression of an inverse Laplace transform is obtained. With construction of dynamical matrices in the virtual domain, a semi-analytical form of the time-history kernel functions for an arbitrary boundary in an arbitrary lattice can be found. The time-history kernel functions for different crystal lattices are derived to show the generality of the proposed method. Non-equilibrium MD simulations in a triangular lattice with and without the absorbing boundary condition are conducted to demonstrate the validity of the solution.

  20. Gyrokinetic particle simulation of microturbulence for general magnetic geometry and experimental profiles

    SciTech Connect

    Xiao, Yong; Holod, Ihor; Wang, Zhixuan; Lin, Zhihong; Zhang, Taige

    2015-02-15

    Developments in gyrokinetic particle simulation enable the gyrokinetic toroidal code (GTC) to simulate turbulent transport in tokamaks with realistic equilibrium profiles and plasma geometry, which is a critical step in the code–experiment validation process. These new developments include numerical equilibrium representation using B-splines, a new Poisson solver based on finite difference using field-aligned mesh and magnetic flux coordinates, a new zonal flow solver for general geometry, and improvements on the conventional four-point gyroaverage with nonuniform background marker loading. The gyrokinetic Poisson equation is solved in the perpendicular plane instead of the poloidal plane. Exploiting these new features, GTC is able to simulate a typical DIII-D discharge with experimental magnetic geometry and profiles. The simulated turbulent heat diffusivity and its radial profile show good agreement with other gyrokinetic codes. The newly developed nonuniform loading method provides a modified radial transport profile to that of the conventional uniform loading method.

  1. The Tropical Subseasonal Variability Simulated in the NASA GISS General Circulation Model

    NASA Technical Reports Server (NTRS)

    Kim, Daehyun; Sobel, Adam H.; DelGenio, Anthony D.; Chen, Yonghua; Camargo, Suzana J.; Yao, Mao-Sung; Kelley, Maxwell; Nazarenko, Larissa

    2012-01-01

    The tropical subseasonal variability simulated by the Goddard Institute for Space Studies general circulation model, Model E2, is examined. Several versions of Model E2 were developed with changes to the convective parameterization in order to improve the simulation of the Madden-Julian oscillation (MJO). When the convective scheme is modified to have a greater fractional entrainment rate, Model E2 is able to simulate MJO-like disturbances with proper spatial and temporal scales. Increasing the rate of rain reevaporation has additional positive impacts on the simulated MJO. The improvement in MJO simulation comes at the cost of increased biases in the mean state, consistent in structure and amplitude with those found in other GCMs when tuned to have a stronger MJO. By reinitializing a relatively poor-MJO version with restart files from a relatively better-MJO version, a series of 30-day integrations is constructed to examine the impacts of the parameterization changes on the organization of tropical convection. The poor-MJO version with smaller entrainment rate has a tendency to allow convection to be activated over a broader area and to reduce the contrast between dry and wet regimes so that tropical convection becomes less organized. Besides the MJO, the number of tropical-cyclone-like vortices simulated by the model is also affected by changes in the convection scheme. The model simulates a smaller number of such storms globally with a larger entrainment rate, while the number increases significantly with a greater rain reevaporation rate.

  2. Fast Realistic MRI Simulations Based on Generalized Multi-Pool Exchange Tissue Model.

    PubMed

    Liu, Fang; Velikina, Julia V; Block, Walter F; Kijowski, Richard; Samsonov, Alexey A

    2017-02-01

    We present MRiLab, a new comprehensive simulator for large-scale realistic MRI simulations on a regular PC equipped with a modern graphical processing unit (GPU). MRiLab combines realistic tissue modeling with numerical virtualization of an MRI system and scanning experiment to enable assessment of a broad range of MRI approaches including advanced quantitative MRI methods inferring microstructure on a sub-voxel level. A flexible representation of tissue microstructure is achieved in MRiLab by employing the generalized tissue model with multiple exchanging water and macromolecular proton pools rather than a system of independent proton isochromats typically used in previous simulators. The computational power needed for simulation of the biologically relevant tissue models in large 3D objects is gained using parallelized execution on GPU. Three simulated and one actual MRI experiments were performed to demonstrate the ability of the new simulator to accommodate a wide variety of voxel composition scenarios and demonstrate detrimental effects of simplified treatment of tissue micro-organization adapted in previous simulators. GPU execution allowed  ∼ 200× improvement in computational speed over standard CPU. As a cross-platform, open-source, extensible environment for customizing virtual MRI experiments, MRiLab streamlines the development of new MRI methods, especially those aiming to infer quantitatively tissue composition and microstructure.

  3. On the performance of voltage stepping for the simulation of adaptive, nonlinear integrate-and-fire neuronal networks.

    PubMed

    Kaabi, Mohamed Ghaith; Tonnelier, Arnaud; Martinez, Dominique

    2011-05-01

    In traditional event-driven strategies, spike timings are analytically given or calculated with arbitrary precision (up to machine precision). Exact computation is possible only for simplified neuron models, mainly the leaky integrate-and-fire model. In a recent paper, Zheng, Tonnelier, and Martinez (2009) introduced an approximate event-driven strategy, named voltage stepping, that allows the generic simulation of nonlinear spiking neurons. Promising results were achieved in the simulation of single quadratic integrate-and-fire neurons. Here, we assess the performance of voltage stepping in network simulations by considering more complex neurons (quadratic integrate-and-fire neurons with adaptation) coupled with multiple synapses. To handle the discrete nature of synaptic interactions, we recast voltage stepping in a general framework, the discrete event system specification. The efficiency of the method is assessed through simulations and comparisons with a modified time-stepping scheme of the Runge-Kutta type. We demonstrated numerically that the original order of voltage stepping is preserved when simulating connected spiking neurons, independent of the network activity and connectivity.

  4. A measurement-based generalized source model for Monte Carlo dose simulations of CT scans

    NASA Astrophysics Data System (ADS)

    Ming, Xin; Feng, Yuanming; Liu, Ransheng; Yang, Chengwen; Zhou, Li; Zhai, Hezheng; Deng, Jun

    2017-03-01

    The goal of this study is to develop a generalized source model for accurate Monte Carlo dose simulations of CT scans based solely on the measurement data without a priori knowledge of scanner specifications. The proposed generalized source model consists of an extended circular source located at x-ray target level with its energy spectrum, source distribution and fluence distribution derived from a set of measurement data conveniently available in the clinic. Specifically, the central axis percent depth dose (PDD) curves measured in water and the cone output factors measured in air were used to derive the energy spectrum and the source distribution respectively with a Levenberg-Marquardt algorithm. The in-air film measurement of fan-beam dose profiles at fixed gantry was back-projected to generate the fluence distribution of the source model. A benchmarked Monte Carlo user code was used to simulate the dose distributions in water with the developed source model as beam input. The feasibility and accuracy of the proposed source model was tested on a GE LightSpeed and a Philips Brilliance Big Bore multi-detector CT (MDCT) scanners available in our clinic. In general, the Monte Carlo simulations of the PDDs in water and dose profiles along lateral and longitudinal directions agreed with the measurements within 4%/1 mm for both CT scanners. The absolute dose comparison using two CTDI phantoms (16 cm and 32 cm in diameters) indicated a better than 5% agreement between the Monte Carlo-simulated and the ion chamber-measured doses at a variety of locations for the two scanners. Overall, this study demonstrated that a generalized source model can be constructed based only on a set of measurement data and used for accurate Monte Carlo dose simulations of patients’ CT scans, which would facilitate patient-specific CT organ dose estimation and cancer risk management in the diagnostic and therapeutic radiology.

  5. The Early Jurassic climate: General circulation model simulations and the paleoclimate record

    SciTech Connect

    Chandler, M.A.

    1992-01-01

    This thesis presents the results of several general circulation model simulations of the Early Jurassic climate. The general circulation model employed was developed at the Goddard Institute for Space Studies while most paleoclimate data were provided by the Paleographic Atlas Project of the University of Chicago. The first chapter presents an Early Jurassic base simulation, which uses detailed reconstructions of paleogeography, vegetation, and sea surface temperature as boundary condition data sets. The resulting climatology reveals an Earth 5.2[degrees]C warmer, globally, than at present and a latitudinal temperature gradient dominated by high-latitude warming (+20[degrees]C) and little tropical change (+1[degrees]C). Comparisons show a good correlation between simulated results and paleoclimate data. Sensitivity experiments are used to investigate any model-data mismatches. Chapters two and three discuss two important aspects of Early Jurassic climate, continental aridity and global warming. Chapter two focuses on the hydrological capabilities of the general circulation model. The general circulation model's hydrologic diagnostics are evaluated, using the distribution of modern deserts and Early Jurassic paleoclimate data as validating constraints. A new method, based on general circulation model diagnostics and empirical formulae, is proposed for evaluating moisture balance. Chapter three investigates the cause of past global warming, concentrating on the role of increased ocean heat transport. Early Jurassic simulations show that increased ocean heat transports may have been a major factor in past climates. Increased ocean heat transports create latitudinal temperature gradients that closely approximate paleoclimate data and solve the problem of tropical overheating that results from elevated atmospheric carbon dioxide. Increased carbon dioxide cannot duplicate the Jurassic climate without also including increased ocean heat transports.

  6. Simulating of the measurement-device independent quantum key distribution with phase randomized general sources

    PubMed Central

    Wang, Qin; Wang, Xiang-Bin

    2014-01-01

    We present a model on the simulation of the measurement-device independent quantum key distribution (MDI-QKD) with phase randomized general sources. It can be used to predict experimental observations of a MDI-QKD with linear channel loss, simulating corresponding values for the gains, the error rates in different basis, and also the final key rates. Our model can be applicable to the MDI-QKDs with arbitrary probabilistic mixture of different photon states or using any coding schemes. Therefore, it is useful in characterizing and evaluating the performance of the MDI-QKD protocol, making it a valuable tool in studying the quantum key distributions. PMID:24728000

  7. Cloud-radiative effects on implied oceanic energy transports as simulated by atmospheric general circulation models

    SciTech Connect

    Gleckler, P.J.; Randall, D.A.; Boer, G.

    1994-03-01

    This paper reports on energy fluxes across the surface of the ocean as simulated by fifteen atmospheric general circulation models in which ocean surface temperatures and sea-ice boundaries are prescribed. The oceanic meridional energy transport that would be required to balance these surface fluxes is computed, and is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean energy transport can be affected by the errors in simulated cloud-radiation interactions.

  8. Gyrokinetic simulations in general geometry and applications to collisional damping of zonal flows

    SciTech Connect

    Lin, Z.; Hahm, T.S.; Lee, W.W.; Tang, W.M.; White, R.B.

    2000-02-15

    A fully three-dimensional gyrokinetic particle code using magnetic coordinates for general geometry has been developed and applied to the investigation of zonal flows dynamics in toroidal ion-temperature-gradient turbulence. Full torus simulation results support the important conclusion that turbulence-driven zonal flows significantly reduce the turbulent transport. Linear collisionless simulations for damping of an initial poloidal flow perturbation exhibit an asymptotic residual flow. The collisional damping of this residual causes the dependence of ion thermal transport on the ion-ion collision frequency even in regimes where the instabilities are collisionless.

  9. Generalized math model for simulation of high-altitude balloon systems

    NASA Technical Reports Server (NTRS)

    Nigro, N. J.; Elkouh, A. F.; Hinton, D. E.; Yang, J. K.

    1985-01-01

    Balloon systems have proved to be a cost-effective means for conducting research experiments (e.g., infrared astronomy) in the earth's atmosphere. The purpose of this paper is to present a generalized mathematical model that can be used to simulate the motion of these systems once they have attained float altitude. The resulting form of the model is such that the pendulation and spin motions of the system are uncoupled and can be analyzed independently. The model is evaluated by comparing the simulation results with data obtained from an actual balloon system flown by NASA.

  10. Generalized math model for simulation of high-altitude balloon systems

    NASA Technical Reports Server (NTRS)

    Nigro, N. J.; Elkouh, A. F.; Hinton, D. E.; Yang, J. K.

    1985-01-01

    Balloon systems have proved to be a cost-effective means for conducting research experiments (e.g., infrared astronomy) in the earth's atmosphere. The purpose of this paper is to present a generalized mathematical model that can be used to simulate the motion of these systems once they have attained float altitude. The resulting form of the model is such that the pendulation and spin motions of the system are uncoupled and can be analyzed independently. The model is evaluated by comparing the simulation results with data obtained from an actual balloon system flown by NASA.

  11. General-relativistic simulations of binary black hole-neutron stars: Precursor electromagnetic signals

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; Etienne, Zachariah B.; Shapiro, Stuart L.

    2013-07-01

    We perform the first general relativistic force-free simulations of neutron star magnetospheres in orbit about spinning and nonspinning black holes. We find promising precursor electromagnetic emission: typical Poynting luminosities at, e.g., an orbital separation of r=6.6RNS are LEM˜6×1042(BNS,p/1013G)2(MNS/1.4M⊙)2erg/s. The Poynting flux peaks within a broad beam of ˜40° in the azimuthal direction and within ˜60° from the orbital plane, establishing a possible lighthouse effect. Our calculations, though preliminary, preview more detailed simulations of these systems that we plan to perform in the future.

  12. Effects of cumulus convection on the simulated monsoon circulation in a general circulation model

    SciTech Connect

    Zhang, Guang Jun )

    1994-09-01

    The effect of cumulus convection on the Asian summer monsoon circulation is investigated, using a general circulation model. Two simulations for the summer months (June, July, and August) are performed, one parameterizing convection using a mass flux scheme and the other without convective parameterization. The results show that convection has significant effects on the monsoon circulation and its associated precipitation. In the simulation with the mass flux convective parameterization, precipitation in the western Pacific is decreased, together with a decrease in surface evaporation and wind speed. In the indian monsoon region it is almost the opposite. Comparison with a simulation using moist convective adjustment to parameterize convection shows that the monsoon circulation and precipitation distribution in the no-convection simulation are very similar to those in the simulation with moist convective adjustment. The difference in the large-scale circulation with and without convective parameterization is interpreted in terms of convective stabilization of the atmosphere by convection, using dry and moist static energy budgets. It is shown that weakening of the low-level convergence in the western Pacific in the simulation with convection is closely associated with the stabilization of the atmosphere by convection, mostly through drying of the lower troposphere; changes in low-level convergence lead to changes in precipitation. The precipitation increase in the Indian monsoon can be explained similarly. 29 refs., 12 figs.

  13. A General Relativistic Magnetohydrodynamics Simulation of Jet Formation with a State Transition

    NASA Technical Reports Server (NTRS)

    Nishikawa, K. I.; Richardson, G.; Koide, S.; Shibata, K.; Kudoh, T.; Hardee, P.; Fushman, G. J.

    2004-01-01

    We have performed the first fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity sim 0.3c) is created as shown by previous two-dimensional axisymmetric simulations with mirror symmetry at the equator. The 3-D simulation ran over one hundred light-crossing time units which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted due in part to magnetic pressure from the twisting the initially uniform magnetic field and from gas pressure associated with shock formation. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outwards with a wider angle than the initial jet. The widening of the jet is consistent with the outward moving shock wave. This evolution of jet-disk coupling suggests that the low/hard state of the jet system may switch to the high/soft state with a wind, as the accretion rate diminishes.

  14. A generalized mathematical framework for stochastic simulation and forecast of hydrologic time series

    NASA Astrophysics Data System (ADS)

    Koutsoyiannis, Demetris

    2000-02-01

    A generalized framework for single-variate and multivariate simulation and forecasting problems in stochastic hydrology is proposed. It is appropriate for short-term or long-term memory processes and preserves the Hurst coefficient even in multivariate processes with a different Hurst coefficient in each location. Simultaneously, it explicitly preserves the coefficients of skewness of the processes. The proposed framework incorporates short-memory (autoregressive moving average) and long-memory (fractional Gaussian noise) models, considering them as special instances of a parametrically defined generalized autocovariance function, more comprehensive than those used in these classes of models. The generalized autocovariance function is then implemented in a generalized moving average generating scheme that yields a new time-symmetric (backward-forward) representation, whose advantages are studied. Fast algorithms for computation of internal parameters of the generating scheme are developed, appropriate for problems including even thousands of such parameters. The proposed generating scheme is also adapted through a generalized methodology to perform in forecast mode, in addition to simulation mode. Finally, a specific form of the model for problems where the autocorrelation function can be defined only for a certain finite number of lags is also studied. Several illustrations are included to clarify the features and the performance of the components of the proposed framework.

  15. Generalized-ensemble simulations of the human parathyroid hormone fragment PTH(1-34)

    NASA Astrophysics Data System (ADS)

    Hansmann, Ulrich H. E.

    2004-01-01

    A generalized-ensemble technique, multicanonical sampling, is used to study the folding of a 34-residue human parathyroid hormone fragment. An all-atom model of the peptide is employed and the protein-solvent interactions are approximated by an implicit solvent. Our results demonstrate that generalized-ensemble simulations are well suited to sample low-energy structures of such large polypeptides. Configurations with a root-mean-square deviation to the crystal structure of less than 1 Å are found. Finally, we discuss limitations of our implicit solvent model.

  16. High frequency scattering by a smooth coated cylinder simulated with generalized impedance boundary conditions

    NASA Technical Reports Server (NTRS)

    Syed, Hasnain H.; Volakis, John L.

    1991-01-01

    Rigorous uniform geometrical theory of diffraction (UGTD) diffraction coefficients are presented for a coated convex cylinder simulated with generalized impedance boundary conditions. In particular, ray solutions are obtained which remain valid in the transition region and reduce uniformly to those in the deep lit and shadow regions. These involve new transition functions in place of the usual Fock-type integrals, characteristic to the impedance cylinder. A uniform asymptotic solution is also presented for observations in the close vicinity of the cylinder. As usual, the diffraction coefficients for the convex cylinder are obtained via a generalization of the corresponding ones for the circular cylinder.

  17. Simulator Evaluation of Runway Incursion Prevention Technology for General Aviation Operations

    NASA Technical Reports Server (NTRS)

    Jones, Denise R.; Prinzel, Lawrence J., III

    2011-01-01

    A Runway Incursion Prevention System (RIPS) has been designed under previous research to enhance airport surface operations situation awareness and provide cockpit alerts of potential runway conflict, during transport aircraft category operations, in order to prevent runway incidents while also improving operations capability. This study investigated an adaptation of RIPS for low-end general aviation operations using a fixed-based simulator at the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC). The purpose of the study was to evaluate modified RIPS aircraft-based incursion detection algorithms and associated alerting and airport surface display concepts for low-end general aviation operations. This paper gives an overview of the system, simulation study, and test results.

  18. Well-posedness and generalized plane waves simulations of a 2D mode conversion model

    SciTech Connect

    Imbert-Gérard, Lise-Marie

    2015-12-15

    Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.

  19. General relativistic simulations of compact binary mergers as engines for short gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios

    2017-04-01

    Black hole—neutron star (BHNS) and neutron star—neutron star (NSNS) binaries are among the favored candidates for the progenitors of the black hole—disk systems that may be the engines powering short-hard gamma ray bursts. After almost two decades of simulations of binary NSNSs and BHNSs in full general relativity we are now beginning to understand the ingredients that may be necessary for these systems to launch incipient jets. Here, we review our current understanding, and summarize the surprises and lessons learned from state-of-the-art (magnetohydrodynamic) simulations in full general relativity of BHNS and NSNS mergers as jet engines for short-hard gamma-ray bursts. We also propose a new approach to probing the nuclear equation of state by virtue of multimessenger observations.

  20. DL_POLY_2.0: a general-purpose parallel molecular dynamics simulation package.

    PubMed

    Smith, W; Forester, T R

    1996-06-01

    DL_POLY_2.0 is a general-purpose parallel molecular dynamics simulation package developed at Daresbury Laboratory under the auspices of the Council for the Central Laboratory of the Research Councils. Written to support academic research, it has a wide range of applications and is designed to run on a wide range of computers: from single processor workstations to parallel supercomputers. Its structure, functionality, performance, and availability are described.

  1. Simulation of charge breeding of rubidium using Monte Carlo charge breeding code and generalized ECRIS model

    SciTech Connect

    Zhao, L.; Cluggish, B.; Kim, J. S.; Pardo, R.; Vondrasek, R.

    2010-02-15

    A Monte Carlo charge breeding code (MCBC) is being developed by FAR-TECH, Inc. to model the capture and charge breeding of 1+ ion beam in an electron cyclotron resonance ion source (ECRIS) device. The ECRIS plasma is simulated using the generalized ECRIS model which has two choices of boundary settings, free boundary condition and Bohm condition. The charge state distribution of the extracted beam ions is calculated by solving the steady state ion continuity equations where the profiles of the captured ions are used as source terms. MCBC simulations of the charge breeding of Rb+ showed good agreement with recent charge breeding experiments at Argonne National Laboratory (ANL). MCBC correctly predicted the peak of highly charged ion state outputs under free boundary condition and similar charge state distribution width but a lower peak charge state under the Bohm condition. The comparisons between the simulation results and ANL experimental measurements are presented and discussed.

  2. Simulation and flight evaluation of a heads-up display for general aviation

    NASA Technical Reports Server (NTRS)

    Harris, R. L., Sr.

    1974-01-01

    A landing-site indicator (LASI) has been devised as a relatively simple heads-up display to show the pilot the magnitude and direction of the aircraft's velocity vector superimposed on the pilot's view of the landing area. A total of 160 landings were performed in a fixed-base simulation program by four pilots with and without the LASI display. These tests showed the display to be of beneficial use in making the approaches more consistent. Some inferences were also made that the physical workload would also be less with its use. The pilots generally agreed that the LASI, as represented in the simulation was a useful landing aid. Additional pilot comments from preliminary flight tests of a breadboard LASI display unit tend to confirm the simulator results.

  3. Simulation and flight evaluation of a head-up landing aid for general aviation

    NASA Technical Reports Server (NTRS)

    Harris, R. L., Sr.; Goode, M. W.; Yenni, K. R.

    1978-01-01

    A head-up general aviation landing aid called a landing site indicator (LASI) was tested in a fixed-base, visual simulator and in an airplane to determine the effectiveness of the LASI. The display, which had a simplified format and method of implementation, presented to the pilot in his line of sight through the windshield a graphic representation of the airplane's velocity vector. In each testing model (simulation of flight), each of 4 pilots made 20 landing approaches with the LASI and 20 approaches without it. The standard deviations of approach and touchdown parameters were considered an indication of pilot consistency. Use of the LASI improved consistency and also reduced elevator, aileron, and rudder control activity. Pilots' comments indicated that the LASI reduced work load. An appendix is included with a discussion of the simulator effectiveness for visual flight tasks.

  4. GOOSE 1.4 -- Generalized Object-Oriented Simulation Environment user`s manual

    SciTech Connect

    Nypaver, D.J.; Abdalla, M.A.; Guimaraes, L.

    1992-11-01

    The Generalized Object-Oriented Simulation Environment (GOOSE) is a new and innovative simulation tool that is being developed by the Simulation Group of the Advanced Controls Program at Oak Ridge National Laboratory. GOOSE is a fully interactive prototype software package that provides users with the capability of creating sophisticated mathematical models of physical systems. GOOSE uses an object-oriented approach to modeling and combines the concept of modularity (building a complex model easily from a collection of previously written components) with the additional features of allowing precompilation, optimization, and testing and validation of individual modules. Once a library of components has been defined and compiled, models can be built and modified without recompilation. This user`s manual provides detailed descriptions of the structure and component features of GOOSE, along with a comprehensive example using a simplified model of a pressurized water reactor.

  5. GOOSE 1. 4 -- Generalized Object-Oriented Simulation Environment user's manual

    SciTech Connect

    Nypaver, D.J. ); Abdalla, M.A. ); Guimaraes, L. , Sao Jose dos Campos, SP . Inst. de Estudos Avancados)

    1992-11-01

    The Generalized Object-Oriented Simulation Environment (GOOSE) is a new and innovative simulation tool that is being developed by the Simulation Group of the Advanced Controls Program at Oak Ridge National Laboratory. GOOSE is a fully interactive prototype software package that provides users with the capability of creating sophisticated mathematical models of physical systems. GOOSE uses an object-oriented approach to modeling and combines the concept of modularity (building a complex model easily from a collection of previously written components) with the additional features of allowing precompilation, optimization, and testing and validation of individual modules. Once a library of components has been defined and compiled, models can be built and modified without recompilation. This user's manual provides detailed descriptions of the structure and component features of GOOSE, along with a comprehensive example using a simplified model of a pressurized water reactor.

  6. Greenhouse gas-induced climate change simulated with the CCS second-generation general circulation model

    SciTech Connect

    Boer, G.J.; Mcfarlane, N.A.; Lazare, M. )

    1992-10-01

    The Canadian Climate Centre second-generation atmospheric general circulation model coupled to a mixed-layer ocean incorporating thermodynamic sea ice is used to simulate the equilibrium climate response to a doubling of CO[sub 2]. The results of the simulation indicate a global annual warming of 3.5 C with enhanced warming found over land and at higher latitudes. Precipitation and evaporation rates increase by about 4 percent, and cloud cover decreases by 2.2 percent. Soil moisture decreases over continental Northern Hemisphere land areas in summer. The frozen component of soil moisture decreases and the liquid component increases in association with the increase of temperature at higher latitudes. The simulated accumulation rate of permanent snow cover decreases markedly over Greenland and increases slightly over Antarctica. Seasonal snow and sea ice boundaries retreat, but local decreases in planetary albedo are counteracted by tropical increases, so there is little change in the global average. 39 refs.

  7. The rationale for combining an online audiovisual curriculum with simulation to better educate general surgery trainees.

    PubMed

    AlJamal, Yazan N; Ali, Shahzad M; Ruparel, Raaj K; Brahmbhatt, Rushin D; Yadav, Siddhant; Farley, David R

    2014-09-01

    Surgery interns' training has historically been weighted toward patient care, operative observation, and sleeping when possible. With more protected free time and less clinical time, real educational hours for trainees in 2013 are precious. We created a 20-session (3 hours each) simulation curriculum (with pre- and post-tests) and a 24/7 online audiovisual (AV) curriculum for surgery interns. Friday morning simulation sessions emphasize operative skills and judgment. AV clips (using operating room, whiteboard, and simulation center videos) take learners through 20 different general surgery operations with follow-up quizzes. We report our early experience with this novel setup. Thirty-two surgical interns (2012-2013) attended simulation sessions on 20 separate subjects (hernia, breast, hepatobiliary, endocrine, etc). Post-test scores improved (P < .05) and trainees enjoyed using surgical skills for 3 hours each Friday morning (mean, >4.5; Likert scale, 1-5). The AV curriculum feedback is similar (mean, >4.3) and usage is available 24/7 preparing learners for both operating room and simulation sessions. Most simulation sessions utilize low-fidelity models to keep costs <$50 per session. Scores on our semiannual Surgical Olympics (mean score of 49.6 in July vs 82.9 in January; P < .05) improved significantly, suggesting that interns are improving their surgical skills and knowledge. Residents enjoy and learn from the step-by-step, in-house, AV curriculum and both appreciate and thrive on the 'hands-on' simulation sessions mimicking operations they see in real operating rooms. The cost of these programs is not prohibitive and the programs offer simulated repetitions for duty-hour-regulated trainees. Copyright © 2014 Mosby, Inc. All rights reserved.

  8. Towards Observational Astronomy of Jets in Active Galaxies from General Relativistic Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Anantua, Richard; Roger Blandford, Jonathan McKinney and Alexander Tchekhovskoy

    2016-01-01

    We carry out the process of "observing" simulations of active galactic nuclei (AGN) with relativistic jets (hereafter called jet/accretion disk/black hole (JAB) systems) from ray tracing between image plane and source to convolving the resulting images with a point spread function. Images are generated at arbitrary observer angle relative to the black hole spin axis by implementing spatial and temporal interpolation of conserved magnetohydrodynamic flow quantities from a time series of output datablocks from fully general relativistic 3D simulations. We also describe the evolution of simulations of JAB systems' dynamical and kinematic variables, e.g., velocity shear and momentum density, respectively, and the variation of these variables with respect to observer polar and azimuthal angles. We produce, at frequencies from radio to optical, fixed observer time intensity and polarization maps using various plasma physics motivated prescriptions for the emissivity function of physical quantities from the simulation output, and analyze the corresponding light curves. Our hypothesis is that this approach reproduces observed features of JAB systems such as superluminal bulk flow projections and quasi-periodic oscillations in the light curves more closely than extant stylized analytical models, e.g., cannonball bulk flows. Moreover, our development of user-friendly, versatile C++ routines for processing images of state-of-the-art simulations of JAB systems may afford greater flexibility for observing a wide range of sources from high power BL-Lacs to low power quasars (possibly with the same simulation) without requiring years of observation using multiple telescopes. Advantages of observing simulations instead of observing astrophysical sources directly include: the absence of a diffraction limit, panoramic views of the same object and the ability to freely track features. Light travel time effects become significant for high Lorentz factor and small angles between

  9. Biomembrane simulations of 12 lipid types using the general amber force field in a tensionless ensemble.

    PubMed

    Coimbra, João T S; Sousa, Sérgio F; Fernandes, Pedro A; Rangel, Maria; Ramos, Maria J

    2014-01-01

    The AMBER family of force fields is one of the most commonly used alternatives to describe proteins and drug-like molecules in molecular dynamics simulations. However, the absence of a specific set of parameters for lipids has been limiting the widespread application of this force field in biomembrane simulations, including membrane protein simulations and drug-membrane simulations. Here, we report the systematic parameterization of 12 common lipid types consistent with the General Amber Force Field (GAFF), with charge-parameters determined with RESP at the HF/6-31G(d) level of theory, to be consistent with AMBER. The accuracy of the scheme was evaluated by comparing predicted and experimental values for structural lipid properties in MD simulations in an NPT ensemble with explicit solvent in 100:100 bilayer systems. Globally, a consistent agreement with experimental reference data on membrane structures was achieved for some lipid types when using the typical MD conditions normally employed when handling membrane proteins and drug-membrane simulations (a tensionless NPT ensemble, 310 K), without the application of any of the constraints often used in other biomembrane simulations (such as the surface tension and the total simulation box area). The present set of parameters and the universal approach used in the parameterization of all the lipid types described here, as well as the consistency with the AMBER force field family, together with the tensionless NPT ensemble used, opens the door to systematic studies combining lipid components with small drug-like molecules or membrane proteins and show the potential of GAFF in dealing with biomembranes.

  10. Simulation-trained junior residents perform better than general surgeons on advanced laparoscopic cases.

    PubMed

    Boza, Camilo; León, Felipe; Buckel, Erwin; Riquelme, Arnoldo; Crovari, Fernando; Martínez, Jorge; Aggarwal, Rajesh; Grantcharov, Teodor; Jarufe, Nicolás; Varas, Julián

    2017-01-01

    Multiple simulation training programs have demonstrated that effective transfer of skills can be attained and applied into a more complex scenario, but evidence regarding transfer to the operating room is limited. To assess junior residents trained with simulation performing an advanced laparoscopic procedure in the OR and compare results to those of general surgeons without simulation training and expert laparoscopic surgeons. Experimental study: After a validated 16-session advanced laparoscopy simulation training program, junior trainees were compared to general surgeons (GS) with no simulation training and expert bariatric surgeons (BS) in performing a stapled jejuno-jejunostomy (JJO) in the OR. Global rating scale (GRS) and specific rating scale scores, operative time and the distance traveled by both hands measured with a tracking device, were assessed. In addition, all perioperative and immediate postoperative morbidities were registered. Ten junior trainees, 12 GS and 5 BS experts were assessed performing a JJO in the OR. All trainees completed the entire JJO in the OR without any takeovers by the BS. Six (50 %) BS takeovers took place in the GS group. Trainees had significantly better results in all measured outcomes when compared to GS with considerable higher GRS median [19.5 (18.8-23.5) vs. 12 (9-13.8) p < 0.001] and lower operative time. One morbidity was registered; a patient in the trainees group was readmitted at postoperative day 10 for mechanical ileus that resolved with medical treatment. This study demonstrated transfer of advanced laparoscopic skills acquired through a simulated training program in novice surgical residents to the OR.

  11. Arctic storms simulated in atmospheric general circulation models under uniform high, uniform low, and variable resolutions

    NASA Astrophysics Data System (ADS)

    Roesler, E. L.; Bosler, P. A.; Taylor, M.

    2016-12-01

    The impact of strong extratropical storms on coastal communities is large, and the extent to which storms will change with a warming Arctic is unknown. Understanding storms in reanalysis and in climate models is important for future predictions. We know that the number of detected Arctic storms in reanalysis is sensitive to grid resolution. To understand Arctic storm sensitivity to resolution in climate models, we describe simulations designed to identify and compare Arctic storms at uniform low resolution (1 degree), at uniform high resolution (1/8 degree), and at variable resolution (1 degree to 1/8 degree). High-resolution simulations resolve more fine-scale structure and extremes, such as storms, in the atmosphere than a uniform low-resolution simulation. However, the computational cost of running a globally uniform high-resolution simulation is often prohibitive. The variable resolution tool in atmospheric general circulation models permits regional high-resolution solutions at a fraction of the computational cost. The storms are identified using the open-source search algorithm, Stride Search. The uniform high-resolution simulation has over 50% more storms than the uniform low-resolution and over 25% more storms than the variable resolution simulations. Storm statistics from each of the simulations is presented and compared with reanalysis. We propose variable resolution as a cost-effective means of investigating physics/dynamics coupling in the Arctic environment. Future work will include comparisons with observed storms to investigate tuning parameters for high resolution models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2016-7402 A

  12. High-resolution numerical simulation of Venus atmosphere by AFES (Atmospheric general circulation model For the Earth Simulator)

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko; AFES project Team

    2016-10-01

    We have developed an atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) and performed a high-resolution simulation (e.g., Sugimoto et al., 2014a). The highest resolution is T639L120; 1920 times 960 horizontal grids (grid intervals are about 20 km) with 120 vertical layers (layer intervals are about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal and semi-diurnal components. The infrared radiative process is simplified by adopting Newtonian cooling approximation. The temperature is relaxed to a prescribed horizontally uniform temperature distribution, in which a layer with almost neutral static stability observed in the Venus atmosphere presents. A fast zonal wind in a solid-body rotation is given as the initial state.Starting from this idealized superrotation, the model atmosphere reaches a quasi-equilibrium state within 1 Earth year and this state is stably maintained for more than 10 Earth years. The zonal-mean zonal flow with weak midlatitude jets has almost constant velocity of 120 m/s in latitudes between 45°S and 45°N at the cloud top levels, which agrees very well with observations. In the cloud layer, baroclinic waves develop continuously at midlatitudes and generate Rossby-type waves at the cloud top (Sugimoto et al., 2014b). At the polar region, warm polar vortex surrounded by a cold latitude band (cold collar) is well reproduced (Ando et al., 2016). As for horizontal kinetic energy spectra, divergent component is broadly (k > 10) larger than rotational component compared with that on Earth (Kashimura et al., in preparation). We will show recent results of the high-resolution run, e.g., small-scale gravity waves attributed to large-scale thermal tides. Sugimoto, N. et al. (2014a), Baroclinic modes in the Venus atmosphere simulated by GCM, Journal of Geophysical Research: Planets, Vol. 119, p1950-1968.Sugimoto, N. et al. (2014b), Waves in a Venus general

  13. Using Beowulf clusters to speed up neural simulations.

    PubMed

    Smith, Leslie S.

    2002-06-01

    Simulation of large neural systems on PCs requires large amounts of memory, and takes a long time. Parallel computers can speed them up. A new form of parallel computer, the Beowulf cluster, is an affordable version. Event-driven simulation and processor farming are two ways of exploiting this parallelism in neural simulations.

  14. Physical formulation and numerical algorithm for simulating N immiscible incompressible fluids involving general order parameters

    SciTech Connect

    Dong, S.

    2015-02-15

    We present a family of physical formulations, and a numerical algorithm, based on a class of general order parameters for simulating the motion of a mixture of N (N⩾2) immiscible incompressible fluids with given densities, dynamic viscosities, and pairwise surface tensions. The N-phase formulations stem from a phase field model we developed in a recent work based on the conservations of mass/momentum, and the second law of thermodynamics. The introduction of general order parameters leads to an extremely strongly-coupled system of (N−1) phase field equations. On the other hand, the general form enables one to compute the N-phase mixing energy density coefficients in an explicit fashion in terms of the pairwise surface tensions. We show that the increased complexity in the form of the phase field equations associated with general order parameters in actuality does not cause essential computational difficulties. Our numerical algorithm reformulates the (N−1) strongly-coupled phase field equations for general order parameters into 2(N−1) Helmholtz-type equations that are completely de-coupled from one another. This leads to a computational complexity comparable to that for the simplified phase field equations associated with certain special choice of the order parameters. We demonstrate the capabilities of the method developed herein using several test problems involving multiple fluid phases and large contrasts in densities and viscosities among the multitude of fluids. In particular, by comparing simulation results with the Langmuir–de Gennes theory of floating liquid lenses we show that the method using general order parameters produces physically accurate results for multiple fluid phases.

  15. Spectral energetics of the observed and simulated Northern Hemisphere general circulation during blocking episodes

    NASA Technical Reports Server (NTRS)

    Kung, Ernest C.; Baker, Wayman E.

    1986-01-01

    The spectral energetics of the Northern Hemisphere circulation during blocking episodes of the FGGE year is investigated with gridded analyses of observational data and parallel simulation experiments. The purpose of this study is to describe the energetics distinctions of the observed and simulated blockings in the context of the general circulation and to assess the capability of the model to simulate blockings. In the observed circulation a pronounced winter blocking is developed and maintained by the nonlinear wave-wave interaction L(1) from the kinetic energy source for n = 3-10, where L(n) is the transfer of eddy kinetic energy from all other wavenumbers to wavenumber n. In the case of the double blocking in the winter, both L(1) and L(2) support the blocking. The kinetic energy source of n = 10 for upscale input at n = 1 and 2 is supported by the baroclinic conversion at n = 3-10. The simulated winter circulation shows strong baroclinic conversion at all wavenumbers, including ultralong waves. However, the simulation fails to produce pronounced blocking for the absence of L(1), and the converted energy cascades down to shorter waves. The wave-mean transfer of kinetic energy from the large-scale disturbances to the zonal mean component further prevents the accumulation of the kinetic energy at the ultralong waves. In contrast to the winter situation, the summer blocking seems to be directly supported by both L(4) and baroclinic conversion at other planetary-scale waves. Consequently, the summer circulation is better simulated than the winter circulation.

  16. Evaluation of the Event Driven Phenology Model Coupled with the VegET Evapotranspiration Model Through Comparisons with Reference Datasets in a Spatially Explicit Manner

    NASA Technical Reports Server (NTRS)

    Kovalskyy, V.; Henebry, G. M.; Adusei, B.; Hansen, M.; Roy, D. P.; Senay, G.; Mocko, D. M.

    2011-01-01

    A new model coupling scheme with remote sensing data assimilation was developed for estimation of daily actual evapotranspiration (ET). The scheme represents a mix of the VegET, a physically based model to estimate ET from a water balance, and an event driven phenology model (EDPM), where the EDPM is an empirically derived crop specific model capable of producing seasonal trajectories of canopy attributes. In this experiment, the scheme was deployed in a spatially explicit manner within the croplands of the Northern Great Plains. The evaluation was carried out using 2007-2009 land surface forcing data from the North American Land Data Assimilation System (NLDAS) and crop maps derived from remotely sensed data of NASA's Moderate Resolution Imaging Spectroradiometer (MODIS). We compared the canopy parameters produced by the phenology model with normalized difference vegetation index (NDVI) data derived from the MODIS nadir bi-directional reflectance distribution function (BRDF) adjusted reflectance (NBAR) product. The expectations of the EDPM performance in prognostic mode were met, producing determination coefficient (r2) of 0.8 +/-.0.15. Model estimates of NDVI yielded root mean square error (RMSE) of 0.1 +/-.0.035 for the entire study area. Retrospective correction of canopy dynamics with MODIS NDVI brought the errors down to just below 10% of observed data range. The ET estimates produced by the coupled scheme were compared with ones from the MODIS land product suite. The expected r2=0.7 +/-.15 and RMSE = 11.2 +/-.4 mm per 8 days were met and even exceeded by the coupling scheme0 functioning in both prognostic and retrospective modes. Minor setbacks of the EDPM and VegET performance (r2 about 0.5 and additional 30 % of RMSR) were found on the peripheries of the study area and attributed to the insufficient EDPM training and to spatially varying accuracy of crop maps. Overall the experiment provided sufficient evidence of soundness and robustness of the EDPM and

  17. Routine Microsecond Molecular Dynamics Simulations with AMBER on GPUs. 1. Generalized Born

    PubMed Central

    2012-01-01

    We present an implementation of generalized Born implicit solvent all-atom classical molecular dynamics (MD) within the AMBER program package that runs entirely on CUDA enabled NVIDIA graphics processing units (GPUs). We discuss the algorithms that are used to exploit the processing power of the GPUs and show the performance that can be achieved in comparison to simulations on conventional CPU clusters. The implementation supports three different precision models in which the contributions to the forces are calculated in single precision floating point arithmetic but accumulated in double precision (SPDP), or everything is computed in single precision (SPSP) or double precision (DPDP). In addition to performance, we have focused on understanding the implications of the different precision models on the outcome of implicit solvent MD simulations. We show results for a range of tests including the accuracy of single point force evaluations and energy conservation as well as structural properties pertainining to protein dynamics. The numerical noise due to rounding errors within the SPSP precision model is sufficiently large to lead to an accumulation of errors which can result in unphysical trajectories for long time scale simulations. We recommend the use of the mixed-precision SPDP model since the numerical results obtained are comparable with those of the full double precision DPDP model and the reference double precision CPU implementation but at significantly reduced computational cost. Our implementation provides performance for GB simulations on a single desktop that is on par with, and in some cases exceeds, that of traditional supercomputers. PMID:22582031

  18. Digital-analog quantum simulation of generalized Dicke models with superconducting circuits

    PubMed Central

    Lamata, Lucas

    2017-01-01

    We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits. PMID:28256559

  19. Digital-analog quantum simulation of generalized Dicke models with superconducting circuits.

    PubMed

    Lamata, Lucas

    2017-03-03

    We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits.

  20. Nonparametric simulation-based statistics for detecting linkage in general pedigrees.

    PubMed Central

    Davis, S.; Schroeder, M.; Goldin, L. R.; Weeks, D. E.

    1996-01-01

    We present here four nonparametric statistics for linkage analysis that test whether pairs of affected relatives share marker alleles more often than expected. These statistics are based on simulating the null distribution of a given statistic conditional on the unaffecteds' marker genotypes. Each statistic uses a different measure of marker sharing: the SimAPM statistic uses the simulation-based affected-pedigree-member measure based on identity-by-state (IBS) sharing. The SimKIN (kinship) measure is 1.0 for identity-by-descent (IBD) sharing, 0.0 for no IBD status sharing, and the kinship coefficient when the IBD status is ambiguous. The simulation-based IBD (SimIBD) statistic uses a recursive algorithm to determine the probability of two affecteds sharing a specific allele IBD. The SimISO statistic is identical to SimIBD, except that it also measures marker similarity between unaffected pairs. We evaluated our statistics on data simulated under different two-locus disease models, comparing our results to those obtained with several other nonparametric statistics. Use of IBD information produces dramatic increases in power over the SimAPM method, which uses only IBS information. The power of our best statistic in most cases meets or exceeds the power of the other nonparametric statistics. Furthermore, our statistics perform comparisons between all affected relative pairs within general pedigrees and are not restricted to sib pairs or nuclear families. PMID:8644751

  1. Digital-analog quantum simulation of generalized Dicke models with superconducting circuits

    NASA Astrophysics Data System (ADS)

    Lamata, Lucas

    2017-03-01

    We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits.

  2. General-relativistic Large-eddy Simulations of Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Radice, David

    2017-03-01

    The flow inside remnants of binary neutron star (NS) mergers is expected to be turbulent, because of magnetohydrodynamics instability activated at scales too small to be resolved in simulations. To study the large-scale impact of these instabilities, we develop a new formalism, based on the large-eddy simulation technique, for the modeling of subgrid-scale turbulent transport in general relativity. We apply it, for the first time, to the simulation of the late-inspiral and merger of two NSs. We find that turbulence can significantly affect the structure and survival time of the merger remnant, as well as its gravitational-wave (GW) and neutrino emissions. The former will be relevant for GW observation of merging NSs. The latter will affect the composition of the outflow driven by the merger and might influence its nucleosynthetic yields. The accretion rate after black hole formation is also affected. Nevertheless, we find that, for the most likely values of the turbulence mixing efficiency, these effects are relatively small and the GW signal will be affected only weakly by the turbulence. Thus, our simulations provide a first validation of all existing post-merger GW models.

  3. Nonparametric simulation-based statistics for detecting linkage in general pedigrees

    SciTech Connect

    Davis, S.; Schroeder, M.; Weeks, D.E.; Goldin, L.R.

    1996-04-01

    We present here four nonparametric statistics for linkage analysis that test whether pairs of affected relatives share marker alleles more often than expected. These statistics are based on simulating the null distribution of a given statistic conditional on the unaffecteds` marker genotypes. Each statistic uses a different measure of marker sharing: the SimAPM statistic uses the simulation-based affected-pedigree-member measure based on identity-by-state (IBS) sharing. The SimKIN (kinship) measure is 1.0 for identity-by-descent (IBD) sharing, 0.0 for no IBD sharing, and the kinship coefficient when the IBD status is ambiguous. The simulation-based IBD (SimIBD) statistic uses a recursive algorithm to determine the probability of two affecteds sharing a specific allele IBD. The SimISO statistic is identical to SimIBD, except that it also measures marker similarity between unaffected pairs. We evaluated our statistics on data simulated under different two-locus disease models, comparing our results to those obtained with several other nonparametric statistics. Use of IBD information produces dramatic increases in power over the SimAPM method, which uses only IBS information. The power of our best statistic in most cases meets or exceeds the power of the other nonparametric statistics. Furthermore, our statistics perform comparisons between all affected relative pairs within general pedigrees and are not restricted to sib pairs or nuclear families. 32 refs., 5 figs., 6 tabs.

  4. Towards a generalized catchment flood processes simulation system with distributed hydrological model

    NASA Astrophysics Data System (ADS)

    Chen, Y.

    2015-12-01

    High resolution distributed hydrological model is regarded as to have the potential to finely simulate the catchment hydrological processes, but challenges still exist. This paper, presented a generalized catchment flood processes simulation system with Liuxihe Model, a physically-based distributed hydrological model proposed mainly for catchment flood forecasting, which is a process-based hydrological model. In this system, several cutting edge technologies have been employed, such as the supercomputing technology, PSO algorithm for parameter optimization, cloud computation, GIS and software engineering, and it is deployed on a high performance computer with free public accesses. The model structure setting up data used in this system is the open access database, so it could be used for catchments world widely. With the application of parallel computation algorithm, the model spatial resolution could be as fine as up to 100 m grid, while maintaining high computation efficiency, and could be used in large scale catchments. With the utilization of parameter optimization method, the model performance cold be improved largely. The flood events of several catchments in southern China with different drainage sizes have been simulated by this system, and the results show that this system has strong capability in simulating catchment flood events even in large river basins.

  5. A Generalized Fast Frequency Sweep Algorithm for Coupled Circuit-EM Simulations

    SciTech Connect

    Rockway, J D; Champagne, N J; Sharpe, R M; Fasenfest, B

    2004-01-14

    Frequency domain techniques are popular for analyzing electromagnetics (EM) and coupled circuit-EM problems. These techniques, such as the method of moments (MoM) and the finite element method (FEM), are used to determine the response of the EM portion of the problem at a single frequency. Since only one frequency is solved at a time, it may take a long time to calculate the parameters for wideband devices. In this paper, a fast frequency sweep based on the Asymptotic Wave Expansion (AWE) method is developed and applied to generalized mixed circuit-EM problems. The AWE method, which was originally developed for lumped-load circuit simulations, has recently been shown to be effective at quasi-static and low frequency full-wave simulations. Here it is applied to a full-wave MoM solver, capable of solving for metals, dielectrics, and coupled circuit-EM problems.

  6. User's guide for a general purpose dam-break flood simulation model (K-634)

    USGS Publications Warehouse

    Land, Larry F.

    1981-01-01

    An existing computer program for simulating dam-break floods for forecast purposes has been modified with an emphasis on general purpose applications. The original model was formulated, developed and documented by the National Weather Service. This model is based on the complete flow equations and uses a nonlinear implicit finite-difference numerical method. The first phase of the simulation routes a flood wave through the reservoir and computes an outflow hydrograph which is the sum of the flow through the dam 's structures and the gradually developing breach. The second phase routes this outflow hydrograph through the stream which may be nonprismatic and have segments with subcritical or supercritical flow. The results are discharge and stage hydrographs at the dam as well as all of the computational nodes in the channel. From these hydrographs, peak discharge and stage profiles are tabulated. (USGS)

  7. Wang-Landau Reaction Ensemble Method: Simulation of Weak Polyelectrolytes and General Acid-Base Reactions.

    PubMed

    Landsgesell, Jonas; Holm, Christian; Smiatek, Jens

    2017-02-14

    We present a novel method for the study of weak polyelectrolytes and general acid-base reactions in molecular dynamics and Monte Carlo simulations. The approach combines the advantages of the reaction ensemble and the Wang-Landau sampling method. Deprotonation and protonation reactions are simulated explicitly with the help of the reaction ensemble method, while the accurate sampling of the corresponding phase space is achieved by the Wang-Landau approach. The combination of both techniques provides a sufficient statistical accuracy such that meaningful estimates for the density of states and the partition sum can be obtained. With regard to these estimates, several thermodynamic observables like the heat capacity or reaction free energies can be calculated. We demonstrate that the computation times for the calculation of titration curves with a high statistical accuracy can be significantly decreased when compared to the original reaction ensemble method. The applicability of our approach is validated by the study of weak polyelectrolytes and their thermodynamic properties.

  8. GENASIS: General Astrophysical Simulation System. I. Refinable Mesh and Nonrelativistic Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Cardall, Christian Y.; Budiardja, Reuben D.; Endeve, Eirik; Mezzacappa, Anthony

    2014-02-01

    GenASiS (General Astrophysical Simulation System) is a new code being developed initially and primarily, though by no means exclusively, for the simulation of core-collapse supernovae on the world's leading capability supercomputers. This paper—the first in a series—demonstrates a centrally refined coordinate patch suitable for gravitational collapse and documents methods for compressible nonrelativistic hydrodynamics. We benchmark the hydrodynamics capabilities of GenASiS against many standard test problems; the results illustrate the basic competence of our implementation, demonstrate the strengths and limitations of the HLLC relative to the HLL Riemann solver in a number of interesting cases, and provide preliminary indications of the code's ability to scale and to function with cell-by-cell fixed-mesh refinement.

  9. General Relativistic Magnetohydrodynamics Simulations of Tilted Black Hole Accretion Flows and Their Radiative Properties

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka; Gammie, C. F.; Dolence, J.; Noble, S. C.

    2013-01-01

    We perform global General Relativistic Magnetohydrodynamics (GRMHD) simulations of non-radiative, magnetized disks that are initially tilted with respect to the black hole's spin axis. We run the simulations with different size and tilt angle of the tori for 2 different resolutions. We also perform radiative transfer using Monte Carlo based code that includes synchrotron emission, absorption and Compton scattering to obtain spectral energy distribution and light curves. Similar work was done by Fragile et al. (2007) and Dexter & Fragile (2012) to model the super massive black hole SgrA* with tilted accretion disks. We compare our results of fully conservative hydrodynamic code and spectra that include X-ray, with their results.

  10. Automated procedure for developing hybrid computer simulations of turbofan engines. Part 1: General description

    NASA Technical Reports Server (NTRS)

    Szuch, J. R.; Krosel, S. M.; Bruton, W. M.

    1982-01-01

    A systematic, computer-aided, self-documenting methodology for developing hybrid computer simulations of turbofan engines is presented. The methodology that is pesented makes use of a host program that can run on a large digital computer and a machine-dependent target (hybrid) program. The host program performs all the calculations and data manipulations that are needed to transform user-supplied engine design information to a form suitable for the hybrid computer. The host program also trims the self-contained engine model to match specified design-point information. Part I contains a general discussion of the methodology, describes a test case, and presents comparisons between hybrid simulation and specified engine performance data. Part II, a companion document, contains documentation, in the form of computer printouts, for the test case.

  11. Dust Emissions, Transport, and Deposition Simulated with the NASA Finite-Volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Colarco, Peter; daSilva, Arlindo; Ginoux, Paul; Chin, Mian; Lin, S.-J.

    2003-01-01

    Mineral dust aerosols have radiative impacts on Earth's atmosphere, have been implicated in local and regional air quality issues, and have been identified as vectors for transporting disease pathogens and bringing mineral nutrients to terrestrial and oceanic ecosystems. We present for the first time dust simulations using online transport and meteorological analysis in the NASA Finite-Volume General Circulation Model (FVGCM). Our dust formulation follows the formulation in the offline Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport Model (GOCART) using a topographical source for dust emissions. We compare results of the FVGCM simulations with GOCART, as well as with in situ and remotely sensed observations. Additionally, we estimate budgets of dust emission and transport into various regions.

  12. Dust Emissions, Transport, and Deposition Simulated with the NASA Finite-Volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Colarco, Peter; daSilva, Arlindo; Ginoux, Paul; Chin, Mian; Lin, S.-J.

    2003-01-01

    Mineral dust aerosols have radiative impacts on Earth's atmosphere, have been implicated in local and regional air quality issues, and have been identified as vectors for transporting disease pathogens and bringing mineral nutrients to terrestrial and oceanic ecosystems. We present for the first time dust simulations using online transport and meteorological analysis in the NASA Finite-Volume General Circulation Model (FVGCM). Our dust formulation follows the formulation in the offline Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport Model (GOCART) using a topographical source for dust emissions. We compare results of the FVGCM simulations with GOCART, as well as with in situ and remotely sensed observations. Additionally, we estimate budgets of dust emission and transport into various regions.

  13. GENERAL-RELATIVISTIC SIMULATIONS OF THREE-DIMENSIONAL CORE-COLLAPSE SUPERNOVAE

    SciTech Connect

    Ott, Christian D.; Abdikamalov, Ernazar; Moesta, Philipp; Haas, Roland; Drasco, Steve; O'Connor, Evan P.; Reisswig, Christian; Meakin, Casey A.; Schnetter, Erik

    2013-05-10

    We study the three-dimensional (3D) hydrodynamics of the post-core-bounce phase of the collapse of a 27 M{sub Sun} star and pay special attention to the development of the standing accretion shock instability (SASI) and neutrino-driven convection. To this end, we perform 3D general-relativistic simulations with a three-species neutrino leakage scheme. The leakage scheme captures the essential aspects of neutrino cooling, heating, and lepton number exchange as predicted by radiation-hydrodynamics simulations. The 27 M{sub Sun} progenitor was studied in 2D by Mueller et al., who observed strong growth of the SASI while neutrino-driven convection was suppressed. In our 3D simulations, neutrino-driven convection grows from numerical perturbations imposed by our Cartesian grid. It becomes the dominant instability and leads to large-scale non-oscillatory deformations of the shock front. These will result in strongly aspherical explosions without the need for large-scale SASI shock oscillations. Low-l-mode SASI oscillations are present in our models, but saturate at small amplitudes that decrease with increasing neutrino heating and vigor of convection. Our results, in agreement with simpler 3D Newtonian simulations, suggest that once neutrino-driven convection is started, it is likely to become the dominant instability in 3D. Whether it is the primary instability after bounce will ultimately depend on the physical seed perturbations present in the cores of massive stars. The gravitational wave signal, which we extract and analyze for the first time from 3D general-relativistic models, will serve as an observational probe of the postbounce dynamics and, in combination with neutrinos, may allow us to determine the primary hydrodynamic instability.

  14. SIMPSON: A general simulation program for solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.

    2011-12-01

    A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tel scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple ID experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

  15. SIMPSON: A General Simulation Program for Solid-State NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.

    2000-12-01

    A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tcl scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple 1D experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

  16. Formulation and simulation of the generalized ion viscous stress tensor in magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Addae-Kagyah, Michael K.

    2007-12-01

    Details of the generalized model of the parallel ion viscous stress tensor, pi∥, is presented in this work. Kinetic-based derivation of pi∥, employing a Chapman-Enskog-like (CEL) expansion of the plasma particle distribution function, is part of a broad research effort aimed at incorporating suitable kinetic physics into the physical modeling of tenuous, high-temperature (fusion-grade) plasmas. Often, this goal is achieved through the use of generalized, integral closures in the evolution equations of fluid quantities, which correspond to low-order velocity-space moments of the particle distribution functions. The primary analytical task in the formulation of pi∥ is the derivation of a drift kinetic equation (DKE) from the plasma kinetic equation (via appropriate gyro-averaging and ordering schemes). Next, the time-dependent DKE is solved for the kinetic distortion by reducing it to a system of coupled, linear equations, that results from an expansion in Legendre polynomials, and the correct exploitation of their orthogonality properties. The tensor, pi∥ , is calculated in the final step as a second-order velocity-space moment of the kinetic distortion term in the CEL expansion. This is a steady-state version of pi∥, which is valid for arbitrary collision and transit frequencies. The upgraded theory reproduces Braginskii's pi ∥ in the regime of high collisionality, and agrees with Chang and Callen's results in the nearly collisionless regime. Subsequently, a time-dependent version of pi∥ (incorporating an exact form of linearized Coulomb collision operator) is formulated, as an enhancement to the steady-state model. Numerical simulations of three known physical phenomena in plasmas, incorporating finite effects of the steady-state, generalized pi∥, are executed in slab geometry, using the NIMROD simulation code. Specifically, ion acoustic wave propagation and dissipation, stress-induced ion heating, and parallel ion momentum (or flow) flattening

  17. Terahertz spectroscopic polarimetry of generalized anisotropic media composed of Archimedean spiral arrays: Experiments and simulations.

    PubMed

    Aschaffenburg, Daniel J; Williams, Michael R C; Schmuttenmaer, Charles A

    2016-05-07

    Terahertz time-domain spectroscopic polarimetry has been used to measure the polarization state of all spectral components in a broadband THz pulse upon transmission through generalized anisotropic media consisting of two-dimensional arrays of lithographically defined Archimedean spirals. The technique allows a full determination of the frequency-dependent, complex-valued transmission matrix and eigenpolarizations of the spiral arrays. Measurements were made on a series of spiral array orientations. The frequency-dependent transmission matrix elements as well as the eigenpolarizations were determined, and the eigenpolarizations were found be to elliptically corotating, as expected from their symmetry. Numerical simulations are in quantitative agreement with measured spectra.

  18. Parallel implementation of the FETI-DPEM algorithm for general 3D EM simulations

    NASA Astrophysics Data System (ADS)

    Li, Yu-Jia; Jin, Jian-Ming

    2009-05-01

    A parallel implementation of the electromagnetic dual-primal finite element tearing and interconnecting algorithm (FETI-DPEM) is designed for general three-dimensional (3D) electromagnetic large-scale simulations. As a domain decomposition implementation of the finite element method, the FETI-DPEM algorithm provides fully decoupled subdomain problems and an excellent numerical scalability, and thus is well suited for parallel computation. The parallel implementation of the FETI-DPEM algorithm on a distributed-memory system using the message passing interface (MPI) is discussed in detail along with a few practical guidelines obtained from numerical experiments. Numerical examples are provided to demonstrate the efficiency of the parallel implementation.

  19. An in-flight simulation of lateral control nonlinearities. [for general aviation aircraft

    NASA Technical Reports Server (NTRS)

    Ellis, D. R.; Tilak, N. W.

    1975-01-01

    An in-flight simulation program was conducted to explore, in a generalized way, the influence of spoiler-type roll-control nonlinearities on handling qualities. The roll responses studied typically featured a dead zone or very small effectiveness for small control inputs, a very high effectiveness for mid-range deflections, and low effectiveness again for large inputs. A linear force gradient with no detectable breakout force was provided. Given otherwise good handling characteristics, it was found that moderate nonlinearities of the types tested might yield acceptable roll control, but the best level of handling qualities is obtained with linear, aileron-like control.

  20. Mars atmospheric dynamics as simulated by the NASA Ames General Circulation Model. II - Transient baroclinic eddies

    NASA Technical Reports Server (NTRS)

    Barnes, Jeffrey R.; Pollack, James B.; Haberle, Robert M.; Leovy, Conway B.; Zurek, Richard W.; Lee, Hilda; Schaeffer, James

    1993-01-01

    A large set of experiments performed with the NASA Ames Mars General Circulation Model is analyzed to determine the properties, structure, and dynamics of the simulated transient baroclinic eddies. There is strong transient baroclinic eddy activity in the extratropics of the Northern Hemisphere during the northern autumn, winter, and spring seasons. The eddy activity remains strong for very large dust loadings, though it shifts northward. The eastward propagating eddies are characterized by zonal wavenumbers of 1-4 and periods of about 2-10 days. The properties of the GCM baroclinic eddies in the northern extratropics are compared in detail with analogous properties inferred from Viking Lander meteorology observations.

  1. Terahertz spectroscopic polarimetry of generalized anisotropic media composed of Archimedean spiral arrays: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Aschaffenburg, Daniel J.; Williams, Michael R. C.; Schmuttenmaer, Charles A.

    2016-05-01

    Terahertz time-domain spectroscopic polarimetry has been used to measure the polarization state of all spectral components in a broadband THz pulse upon transmission through generalized anisotropic media consisting of two-dimensional arrays of lithographically defined Archimedean spirals. The technique allows a full determination of the frequency-dependent, complex-valued transmission matrix and eigenpolarizations of the spiral arrays. Measurements were made on a series of spiral array orientations. The frequency-dependent transmission matrix elements as well as the eigenpolarizations were determined, and the eigenpolarizations were found be to elliptically corotating, as expected from their symmetry. Numerical simulations are in quantitative agreement with measured spectra.

  2. Mars atmospheric dynamics as simulated by the NASA AMES General Circulation Model. II - Transient baroclinic eddies

    NASA Astrophysics Data System (ADS)

    Barnes, J. R.; Pollack, J. B.; Haberle, R. M.; Leovy, C. B.; Zurek, R. W.; Lee, H.; Schaeffer, J.

    1993-02-01

    A large set of experiments performed with the NASA Ames Mars General Circulation Model is analyzed to determine the properties, structure, and dynamics of the simulated transient baroclinic eddies. There is strong transient baroclinic eddy activity in the extratropics of the Northern Hemisphere during the northern autumn, winter, and spring seasons. The eddy activity remains strong for very large dust loadings, though it shifts northward. The eastward propagating eddies are characterized by zonal wavenumbers of 1-4 and periods of about 2-10 days. The properties of the GCM baroclinic eddies in the northern extratropics are compared in detail with analogous properties inferred from Viking Lander meteorology observations.

  3. Generalization of vapor pressure lowering effects in an existing geothermal simulator

    SciTech Connect

    Shook, G.M.

    1993-06-01

    Thermodynamic properties of pore water are shown to be different from those of bulk water because of interfacial forces between the aqueous and solid phases. This {open_quotes}vapor-pressure lowering{close_quotes} (VPL) effect is described through Kelvin`s equation, which relates VPL to properties of the liquid phase. An algorithm that accounts for VPL had previously been implented in the geothermal simulator TETRAD. This algorithm applies to a narrow range of reservoir properties, and in some cases leads in inconsistencies. This report presents a generalization of the VPL algorithm which removes many of its limitations. The governing equations for the generalization are presented, assumptions and limitations of the method are discussed, and the modifications are validated.

  4. General Relativistic Simulations of Magnetized Plasmas around Merging Supermassive Black Holes

    NASA Astrophysics Data System (ADS)

    Giacomazzo, Bruno; Baker, John G.; Miller, M. Coleman; Reynolds, Christopher S.; van Meter, James R.

    2012-06-01

    Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this Letter, we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular, we observe a total amplification of the magnetic field of ~2 orders of magnitude, which is driven by the accretion onto the binary and that leads to much stronger electromagnetic signals, more than a factor of 104 larger than comparable calculations done in the force-free regime where such amplifications are not possible.

  5. Development of generalized mapping tools to improve implementation of data driven computer simulations (04-ERD-083)

    SciTech Connect

    Ramirez, A; Pasyanos, M; Franz, G A

    2004-09-17

    The Stochastic Engine (SE) is a data driven computer simulation tool for predicting the characteristics of complex systems. The SE integrates accurate simulators with the Monte Carlo Markov Chain (MCMC) approach (a stochastic inverse technique) to identify alternative models that are consistent with available data and ranks these alternatives according to their probabilities. Implementation of the SE is currently cumbersome owing to the need to customize the pre-processing and processing steps that are required for a specific application. This project widens the applicability of the Stochastic Engine by generalizing some aspects of the method (i.e. model-to-data transformation types, configuration, model representation). We have generalized several of the transformations that are necessary to match the observations to proposed models. These transformations are sufficiently general not to pertain to any single application. This approach provides a framework that increases the efficiency of the SE implementation. The overall goal is to reduce response time and make the approach as ''plug-and-play'' as possible, and will result in the rapid accumulation of new data types for a host of both earth science and non-earth science problems. When adapting the SE approach to a specific application, there are various pre-processing and processing steps that are typically needed to run a specific problem. Many of these steps are common to a wide variety of specific applications. Here we list and describe several data transformations that are common to a variety of subsurface inverse problems. A subset of these steps have been developed in a generalized form such that they could be used with little or no modifications in a wide variety of specific applications. This work was funded by the LDRD Program (tracking number 04-ERD-083).

  6. Tropospheric ozone simulation with a chemistry-general circulation model: Influence of higher hydrocarbon chemistry

    NASA Astrophysics Data System (ADS)

    Roelofs, Geert-Jan; Lelieveld, Jos

    2000-09-01

    We present an improved version of the global chemistry-general circulation model of Roelofs and Lelieveld [1997]. The major model improvement is the representation of higher hydrocarbon chemistry, implemented by means of the Carbon Bond Mechanism 4 (CBM-4). Simulated tropospheric ozone concentrations at remote locations, which agreed well with observations in the previous model version, are not affected much by the chemistry of higher hydrocarbons. However, ozone formation in the polluted boundary layer is significantly enhanced, resulting in a more realistic simulation of surface ozone in regions such as North America, Europe, and Southeast Asia. Our model simulates a net global tropospheric ozone production of 73 Tg yr-1 when higher hydrocarbon chemistry is considered, and -36 Tg yr-1 without higher hydrocarbon chemistry. The simulated seasonality of surface CO agrees well with observations. However, the southern hemispheric maximum for O3 and CO associated with biomass burning emissions is delayed by 1 month compared to the observations, which demonstrates the need for a better representation of biomass burning emissions. Simulated peroxyacetyl nitrate (PAN) concentrations agree well with observed values, although the variability is underestimated. OH decreases strongly in the continental boundary layer due to its reaction with higher hydrocarbons. However, this is almost compensated by an increase of OH over oceans in the lower half of the troposphere. Consideration of higher hydrocarbon chemistry decreases the global annual tropospheric OH concentration by about 8% compared to a background tropospheric chemistry scheme. Further, the radiative forcing by anthropogenically increased tropospheric ozone on the northern hemisphere increases, especially in July. The forcing also increases on the southern hemisphere where biomass burning emissions produce tropospheric ozone, except between December and June, that is, outside the biomass burning season, when ozone

  7. A Novel Approach for Modeling Chemical Reaction in Generalized Fluid System Simulation Program

    NASA Technical Reports Server (NTRS)

    Sozen, Mehmet; Majumdar, Alok

    2002-01-01

    The Generalized Fluid System Simulation Program (GFSSP) is a computer code developed at NASA Marshall Space Flight Center for analyzing steady state and transient flow rates, pressures, temperatures, and concentrations in a complex flow network. The code, which performs system level simulation, can handle compressible and incompressible flows as well as phase change and mixture thermodynamics. Thermodynamic and thermophysical property programs, GASP, WASP and GASPAK provide the necessary data for fluids such as helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, water, a hydrogen, isobutane, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, several refrigerants, nitrogen trifluoride and ammonia. The program which was developed out of need for an easy to use system level simulation tool for complex flow networks, has been used for the following purposes to name a few: Space Shuttle Main Engine (SSME) High Pressure Oxidizer Turbopump Secondary Flow Circuits, Axial Thrust Balance of the Fastrac Engine Turbopump, Pressurized Propellant Feed System for the Propulsion Test Article at Stennis Space Center, X-34 Main Propulsion System, X-33 Reaction Control System and Thermal Protection System, and International Space Station Environmental Control and Life Support System design. There has been an increasing demand for implementing a combustion simulation capability into GFSSP in order to increase its system level simulation capability of a liquid rocket propulsion system starting from the propellant tanks up to the thruster nozzle for spacecraft as well as launch vehicles. The present work was undertaken for addressing this need. The chemical equilibrium equations derived from the second law of thermodynamics and the energy conservation equation derived from the first law of thermodynamics are solved simultaneously by a Newton-Raphson method. The numerical scheme was implemented as a User

  8. Study on general design of dual-DMD based infrared two-band scene simulation system

    NASA Astrophysics Data System (ADS)

    Pan, Yue; Qiao, Yang; Xu, Xi-ping

    2017-02-01

    Mid-wave infrared(MWIR) and long-wave infrared(LWIR) two-band scene simulation system is a kind of testing equipment that used for infrared two-band imaging seeker. Not only it would be qualified for working waveband, but also realize the essence requests that infrared radiation characteristics should correspond to the real scene. Past single-digital micromirror device (DMD) based infrared scene simulation system does not take the huge difference between targets and background radiation into account, and it cannot realize the separated modulation to two-band light beam. Consequently, single-DMD based infrared scene simulation system cannot accurately express the thermal scene model that upper-computer built, and it is not that practical. To solve the problem, we design a dual-DMD based, dual-channel, co-aperture, compact-structure infrared two-band scene simulation system. The operating principle of the system is introduced in detail, and energy transfer process of the hardware-in-the-loop simulation experiment is analyzed as well. Also, it builds the equation about the signal-to-noise ratio of infrared detector in the seeker, directing the system overall design. The general design scheme of system is given, including the creation of infrared scene model, overall control, optical-mechanical structure design and image registration. By analyzing and comparing the past designs, we discuss the arrangement of optical engine framework in the system. According to the main content of working principle and overall design, we summarize each key techniques in the system.

  9. Variable-resolution frameworks for the simulation of tropical cyclones in global atmospheric general circulation models

    NASA Astrophysics Data System (ADS)

    Zarzycki, Colin

    The ability of atmospheric General Circulation Models (GCMs) to resolve tropical cyclones in the climate system has traditionally been difficult. The challenges include adequately capturing storms which are small in size relative to model grids and the fact that key thermodynamic processes require a significant level of parameterization. At traditional GCM grid spacings of 50-300 km tropical cyclones are severely under-resolved, if not completely unresolved. This thesis explores a variable-resolution global model approach that allows for high spatial resolutions in areas of interest, such as low-latitude ocean basins where tropical cyclogenesis occurs. Such GCM designs with multi-resolution meshes serve to bridge the gap between globally-uniform grids and limited area models and have the potential to become a future tool for regional climate assessments. A statically-nested, variable-resolution option has recently been introduced into the Department of Energy/National Center for Atmospheric Research (DoE/NCAR) Community Atmosphere Model's (CAM) Spectral Element (SE) dynamical core. Using an idealized tropical cyclone test, variable-resolution meshes are shown to significantly lessen computational requirements in regional GCM studies. Furthermore, the tropical cyclone simulations are free of spurious numerical errors at the resolution interfaces. Utilizing aquaplanet simulations as an intermediate test between idealized simulations and fully-coupled climate model runs, climate statistics within refined patches are shown to be well-matched to globally-uniform simulations of the same grid spacing. Facets of the CAM version 4 (CAM4) subgrid physical parameterizations are likely too scale sensitive for variable-resolution applications, but the newer CAM5 package is vastly improved in performance at multiple grid spacings. Multi-decadal simulations following 'Atmospheric Model Intercomparison Project' protocols have been conducted with variable-resolution grids. Climate

  10. Simulation of reactive nanolaminates using reduced models: III. Ingredients for a general multidimensional formulation

    SciTech Connect

    Salloum, Maher; Knio, Omar M.

    2010-06-15

    A transient multidimensional reduced model is constructed for the simulation of reaction fronts in Ni/Al multilayers. The formulation is based on the generalization of earlier methodologies developed for quasi-1D axial and normal propagation, specifically by adapting the reduced formalism for atomic mixing and heat release. This approach enables us to focus on resolving the thermal front structure, whose evolution is governed by thermal diffusion and heat release. A mixed integration scheme is used for this purpose, combining an extended-stability, Runge-Kutta-Chebychev (RKC) integration of the diffusion term with exact treatment of the chemical source term. Thus, a detailed description of atomic mixing within individual layers is avoided, which enables transient modeling of the reduced equations of motion in multiple dimensions. Two-dimensional simulations are first conducted of front propagation in composites combining two bilayer periods. Results are compared with the experimental measurements of Knepper et al., which reveal that the reaction velocity can depend significantly on layering frequency. The comparison indicates that, using a concentration-dependent conductivity model, the transient 2D computations can reasonably reproduce the experimental behavior. Additional tests are performed based on 3D computations of surface initiated reactions. Comparison of computed predictions with laser ignition measurements indicates that the computations provide reasonable estimates of ignition thresholds. A detailed discussion is finally provided of potential generalizations and associated hurdles. (author)

  11. General-circulation-model simulations of future snowpack in the western United States

    USGS Publications Warehouse

    McCabe, G.J.; Wolock, D.M.

    1999-01-01

    April 1 snowpack accumulations measured at 311 snow courses in the western United States (U.S.) are grouped using a correlation-based cluster analysis. A conceptual snow accumulation and melt model and monthly temperature and precipitation for each cluster are used to estimate cluster-average April 1 snowpack. The conceptual snow model is subsequently used to estimate future snowpack by using changes in monthly temperature and precipitation simulated by the Canadian Centre for Climate Modeling and Analysis (CCC) and the Hadley Centre for Climate Prediction and Research (HADLEY) general circulation models (GCMs). Results for the CCC model indicate that although winter precipitation is estimated to increase in the future, increases in temperatures will result in large decreases in April 1 snowpack for the entire western US. Results for the HADLEY model also indicate large decreases in April 1 snowpack for most of the western US, but the decreases are not as severe as those estimated using the CCC simulations. Although snowpack conditions are estimated to decrease for most areas of the western US, both GCMs estimate a general increase in winter precipitation toward the latter half of the next century. Thus, water quantity may be increased in the western US; however, the timing of runoff will be altered because precipitation will more frequently occur as rain rather than as snow.

  12. Simulating botulinum neurotoxin with constant pH molecular dynamics in Generalized Born implicit solvent

    NASA Astrophysics Data System (ADS)

    Chen, Yongzhi; Chen, Xin; Deng, Yuefan

    2007-07-01

    A new method was proposed by Mongan et al. for constant pH molecular dynamics simulation and was implemented in AMBER 8 package. Protonation states are modeled with different charge sets, and titrating residues are sampled from a Boltzmann distribution of protonation states. The simulation periodically adopts Monte Carlo sampling based on Generalized Born (GB) derived energies. However, when this approach was applied to a bio-toxin, Botulinum Neurotoxin Type A (BoNT/A) at pH 4.4, 4.7, 5.0, 6.8 and 7.2, the pK predictions yielded by the method were inconsistent with the experimental values. The systems being simulated were divergent. Furthermore, the system behaviors in a very weak acidic solution (pH 6.8) and in a very weak basic solution (pH 7.2) were significantly different from the neutral case (pH 7.0). Hence, we speculate this method may require further study for modeling large biomolecule.

  13. Molecular dynamics simulation on generalized stacking fault energies of FCC metals under preloading stress

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Cheng, Lü; Kiet, Tieu; Zhao, Xing; Pei, Lin-Qing; Guillaume, Michal

    2015-08-01

    Molecular dynamics (MD) simulations are performed to investigate the effects of stress on generalized stacking fault (GSF) energy of three fcc metals (Cu, Al, and Ni). The simulation model is deformed by uniaxial tension or compression in each of [111], [11-2], and [1-10] directions, respectively, before shifting the lattice to calculate the GSF curve. Simulation results show that the values of unstable stacking fault energy (γusf), stable stacking fault energy (γsf), and unstable twin fault energy (γutf) of the three elements can change with the preloaded tensile or compressive stress in different directions. The ratio of γsf/γusf, which is related to the energy barrier for full dislocation nucleation, and the ratio of γutf/γusf, which is related to the energy barrier for twinning formation are plotted each as a function of the preloading stress. The results of this study reveal that the stress state can change the energy barrier of defect nucleation in the crystal lattice, and thereby can play an important role in the deformation mechanism of nanocrystalline material. Project supported by Australia Research Council Discovery Projects (Grant No. DP130103973). L. Zhang, X. Zhao and L. Q. Pei were financially supported by the China Scholarship Council (CSC).

  14. Martian atmospheric gravity waves simulated by a high-resolution general circulation model

    NASA Astrophysics Data System (ADS)

    Kuroda, Takeshi; Yiǧit, Erdal; Medvedev, Alexander S.; Hartogh, Paul

    2016-07-01

    Gravity waves (GWs) significantly affect temperature and wind fields in the Martian middle and upper atmosphere. They are also one of the observational targets of the MAVEN mission. We report on the first simulations with a high-resolution general circulation model (GCM) and present a global distributions of small-scale GWs in the Martian atmosphere. The simulated GW-induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km. For the northern winter solstice, the model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of GWs: mountainous regions and the meandering winter polar jet. Orographic GWs are filtered upon propagating upward, and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities. Wave fluxes are directed mainly against the local wind. GW dissipation in the upper mesosphere generates a body force per unit mass of tens of m s^{-1} per Martian solar day (sol^{-1}), which tends to close the simulated jets. The results represent a realistic surrogate for missing observations, which can be used for constraining GW parameterizations and validating GCMs.

  15. Oceanic dispersion of Fukushima-derived Cs-137 simulated by multiple oceanic general circulation models.

    PubMed

    Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji; Nakayama, Tomoharu; Ishikawa, Yoichi; Miyazawa, Yasumasa; Usui, Norihisa

    2017-10-09

    To understand the concentration and amount of Fukushima-derived Cs-137 in the ocean, this study simulated the oceanic dispersion of Cs-137 by atmospheric and oceanic dispersion simulations. The oceanic dispersion simulations were carried out with an oceanic dispersion model and multiple oceanic general circulation models. The Cs-137 concentrations were sensitive to ocean currents in the coastal, offshore, and open oceans. The mean Cs-137 concentrations of the multiple models relatively well agreed with the observed concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year after the disaster. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year after the disaster. It was suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Global numerical simulations of the rise of vortex-mediated pulsar glitches in full general relativity

    NASA Astrophysics Data System (ADS)

    Sourie, A.; Chamel, N.; Novak, J.; Oertel, M.

    2017-02-01

    In this paper, we study in detail the role of general relativity on the global dynamics of giant pulsar glitches as exemplified by Vela. For this purpose, we carry out numerical simulations of the spin up triggered by the sudden unpinning of superfluid vortices. In particular, we compute the exchange of angular momentum between the core neutron superfluid and the rest of the star within a two-fluid model including both (non-dissipative) entrainment effects and (dissipative) mutual friction forces. Our simulations are based on a quasi-stationary approach using realistic equations of state (EoSs). We show that the evolution of the angular velocities of both fluids can be accurately described by an exponential law. The associated characteristic rise time τr, which can be precisely computed from stationary configurations only, has a form similar to that obtained in the Newtonian limit. However, general relativity changes the structure of the star and leads to additional couplings between the fluids due to frame-dragging effects. As a consequence, general relativity can have a large impact on the actual value of τr: the errors incurred by using Newtonian gravity are thus found to be as large as ˜40 per cent for the models considered. Values of the rise time are calculated for Vela and compared with current observational limits. Finally, we study the amount of gravitational waves emitted during a glitch. Simple expressions are obtained for the corresponding characteristic amplitudes and frequencies. The detectability of glitches through gravitational wave observatories is briefly discussed.

  17. A comparison between general circulation model simulations using two sea surface temperature datasets for January 1979

    NASA Technical Reports Server (NTRS)

    Ose, Tomoaki; Mechoso, Carlos; Halpern, David

    1994-01-01

    Simulations with the UCLA atmospheric general circulation model (AGCM) using two different global sea surface temperature (SST) datasets for January 1979 are compared. One of these datasets is based on Comprehensive Ocean-Atmosphere Data Set (COADS) (SSTs) at locations where there are ship reports, and climatology elsewhere; the other is derived from measurements by instruments onboard NOAA satellites. In the former dataset (COADS SST), data are concentrated along shipping routes in the Northern Hemisphere; in the latter dataset High Resolution Infrared Sounder (HIRS SST), data cover the global domain. Ensembles of five 30-day mean fields are obtained from integrations performed in the perpetual-January mode. The results are presented as anomalies, that is, departures of each ensemble mean from that produced in a control simulation with climatological SSTs. Large differences are found between the anomalies obtained using COADS and HIRS SSTs, even in the Northern Hemisphere where the datasets are most similar to each other. The internal variability of the circulation in the control simulation and the simulated atmospheric response to anomalous forcings appear to be linked in that the pattern of geopotential height anomalies obtained using COADS SSTs resembles the first empirical orthogonal function (EOF 1) in the control simulation. The corresponding pattern obtained using HIRS SSTs is substantially different and somewhat resembles EOF 2 in the sector from central North America to central Asia. To gain insight into the reasons for these results, three additional simulations are carried out with SST anomalies confined to regions where COADS SSTs are substantially warmer than HIRS SSTs. The regions correspond to warm pools in the northwest and northeast Pacific, and the northwest Atlantic. These warm pools tend to produce positive geopotential height anomalies in the northeastern part of the corresponding oceans. Both warm pools in the Pacific produce large

  18. A comparison between general circulation model simulations using two sea surface temperature datasets for January 1979

    NASA Technical Reports Server (NTRS)

    Ose, Tomoaki; Mechoso, Carlos; Halpern, David

    1994-01-01

    Simulations with the UCLA atmospheric general circulation model (AGCM) using two different global sea surface temperature (SST) datasets for January 1979 are compared. One of these datasets is based on Comprehensive Ocean-Atmosphere Data Set (COADS) (SSTs) at locations where there are ship reports, and climatology elsewhere; the other is derived from measurements by instruments onboard NOAA satellites. In the former dataset (COADS SST), data are concentrated along shipping routes in the Northern Hemisphere; in the latter dataset High Resolution Infrared Sounder (HIRS SST), data cover the global domain. Ensembles of five 30-day mean fields are obtained from integrations performed in the perpetual-January mode. The results are presented as anomalies, that is, departures of each ensemble mean from that produced in a control simulation with climatological SSTs. Large differences are found between the anomalies obtained using COADS and HIRS SSTs, even in the Northern Hemisphere where the datasets are most similar to each other. The internal variability of the circulation in the control simulation and the simulated atmospheric response to anomalous forcings appear to be linked in that the pattern of geopotential height anomalies obtained using COADS SSTs resembles the first empirical orthogonal function (EOF 1) in the control simulation. The corresponding pattern obtained using HIRS SSTs is substantially different and somewhat resembles EOF 2 in the sector from central North America to central Asia. To gain insight into the reasons for these results, three additional simulations are carried out with SST anomalies confined to regions where COADS SSTs are substantially warmer than HIRS SSTs. The regions correspond to warm pools in the northwest and northeast Pacific, and the northwest Atlantic. These warm pools tend to produce positive geopotential height anomalies in the northeastern part of the corresponding oceans. Both warm pools in the Pacific produce large

  19. Relations between winter precipitation and atmospheric circulation simulated by the Geophysical Fluid Dynamics Laboratory general circulation model

    USGS Publications Warehouse

    McCabe, G.J.; Dettinger, M.D.

    1995-01-01

    General circulation model (GCM) simulations of atmospheric circulation are more reliable than GCM simulations of temperature and precipitation. In this study, temporal correlations between 700 hPa height anomalies simulated winter precipitation at eight locations in the conterminous United States are compared with corresponding correlations in observations. The objectives are to 1) characterize the relations between atmospheric circulation and winter precipitation simulated by the GFDL, GCM for selected locations in the conterminous USA, ii) determine whether these relations are similar to those found in observations of the actual climate system, and iii) determine if GFDL-simulated precipitation is forced by the same circulation patterns as in the real atmosphere. -from Authors

  20. A simulation study of control and display requirements for zero-experience general aviation pilots

    NASA Technical Reports Server (NTRS)

    Stewart, Eric C.

    1993-01-01

    The purpose of this simulation study was to define the basic human factor requirements for operating an airplane in all weather conditions. The basic human factors requirements are defined as those for an operator who is a complete novice for airplane operations but who is assumed to have automobile driving experience. These operators thus have had no piloting experience or training of any kind. The human factor requirements are developed for a practical task which includes all of the basic maneuvers required to go from one airport to another airport in limited visibility conditions. The task was quite demanding including following a precise path with climbing and descending turns while simultaneously changing airspeed. The ultimate goal of this research is to increase the utility of general aviation airplanes - that is, to make them a practical mode of transportation for a much larger segment of the general population. This can be accomplished by reducing the training and proficiency requirements of pilots while improving the level of safety. It is believed that advanced technologies such as fly-by-wire (or light), and head-up pictorial displays can be of much greater benefit to the general aviation pilot than to the full-time, professional pilot.

  1. A generalized prestressing algorithm for finite element simulations of preloaded geometries with application to the aorta.

    PubMed

    Weisbecker, Hannah; Pierce, David M; Holzapfel, Gerhard A

    2014-09-01

    Finite element models reconstructed from medical imaging data, for example, computed tomography or MRI scans, generally represent geometries under in vivo load. Classical finite element approaches start from an unloaded reference configuration. We present a generalized prestressing algorithm based on a concept introduced by Gee et al. (Int. J. Num. Meth. Biomed. Eng. 26:52-72, 2012) in which an incremental update of the displacement field in the classical approach is replaced by an incremental update of the deformation gradient field. Our generalized algorithm can be implemented in existing finite element codes with relatively low implementation effort on the element level and is suitable for material models formulated in the current or initial configurations. Applicable to any finite element simulations started from preloaded geometries, we demonstrate the algorithm and its convergence properties on an academic example and on a segment of a thoracic aorta meshed from MRI data. Furthermore, we present an example to discuss the influence of neglecting prestresses in geometries obtained from medical images, a topic on which conflicting statements are found in the literature.

  2. Assessment of the performance of general practitioners by the use of standardized (simulated) patients.

    PubMed Central

    Rethans, J J; Sturmans, F; Drop, R; van der Vleuten, C

    1991-01-01

    A study was undertaken whereby a set of standardized (simulated) patients visited general practitioners without being detected, in a health care system where doctors had fixed patient lists. Thirty nine general practitioners were each visited during normal surgery hours by four standardized patients who were designed to be indistinguishable from real patients. The objective of the study was to see whether the actual performance of general practitioners, as assessed by standardized patients, met predetermined consensus standards of care for actual practice. The patients presented standardized accounts of headache, diarrhoea, shoulder pain and diabetes. The mean group scores of the doctors on the predefined standards of care for the different complaints ranged from 33 to 68%. The results show that standardized patients may be the method of choice in the assessment of the quality of actual care of doctors. It is hypothesized that the substandard scores of the doctors do not reflect inadequate competence, but are a result of the difference between competence and performance. PMID:2031767

  3. Development and Implementation of Non-Newtonian Rheology Into the Generalized Fluid System Simulation Program (GFSSP)

    NASA Technical Reports Server (NTRS)

    DiSalvo, Roberto; Deaconu, Stelu; Majumdar, Alok

    2006-01-01

    One of the goals of this program was to develop the experimental and analytical/computational tools required to predict the flow of non-Newtonian fluids through the various system components of a propulsion system: pipes, valves, pumps etc. To achieve this goal we selected to augment the capabilities of NASA's Generalized Fluid System Simulation Program (GFSSP) software. GFSSP is a general-purpose computer program designed to calculate steady state and transient pressure and flow distributions in a complex fluid network. While the current version of the GFSSP code is able to handle various systems components the implicit assumption in the code is that the fluids in the system are Newtonian. To extend the capability of the code to non-Newtonian fluids, such as silica gelled fuels and oxidizers, modifications to the momentum equations of the code have been performed. We have successfully implemented in GFSSP flow equations for fluids with power law behavior. The implementation of the power law fluid behavior into the GFSSP code depends on knowledge of the two fluid coefficients, n and K. The determination of these parameters for the silica gels used in this program was performed experimentally. The n and K parameters for silica water gels were determined experimentally at CFDRC's Special Projects Laboratory, with a constant shear rate capillary viscometer. Batches of 8:1 (by weight) water-silica gel were mixed using CFDRC s 10-gallon gelled propellant mixer. Prior to testing the gel was allowed to rest in the rheometer tank for at least twelve hours to ensure that the delicate structure of the gel had sufficient time to reform. During the tests silica gel was pressure fed and discharged through stainless steel pipes ranging from 1", to 36", in length and three diameters; 0.0237", 0.032", and 0.047". The data collected in these tests included pressure at tube entrance and volumetric flowrate. From these data the uncorrected shear rate, shear stress, residence time

  4. Head-on collisions of binary white dwarf-neutron stars: Simulations in full general relativity

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; Etienne, Zachariah; Liu, Yuk Tung; Shapiro, Stuart L.

    2011-03-01

    We simulate head-on collisions from rest at large separation of binary white dwarf-neutron stars (WDNSs) in full general relativity. Our study serves as a prelude to our analysis of the circular binary WDNS problem. We focus on compact binaries whose total mass exceeds the maximum mass that a cold-degenerate star can support, and our goal is to determine the fate of such systems. A fully general relativistic hydrodynamic computation of a realistic WDNS head-on collision is prohibitive due to the large range of dynamical time scales and length scales involved. For this reason, we construct an equation of state (EOS) which captures the main physical features of neutron stars (NSs) while, at the same time, scales down the size of white dwarfs (WDs). We call these scaled-down WD models “pseudo-WDs (pWDs).” Using pWDs, we can study these systems via a sequence of simulations where the size of the pWD gradually increases toward the realistic case. We perform two sets of simulations; One set studies the effects of the NS mass on the final outcome, when the pWD is kept fixed. The other set studies the effect of the pWD compaction on the final outcome, when the pWD mass and the NS are kept fixed. All simulations show that after the collision, 14%-18% of the initial total rest mass escapes to infinity. All remnant masses still exceed the maximum rest mass that our cold EOS can support (1.92M⊙), but no case leads to prompt collapse to a black hole. This outcome arises because the final configurations are hot. All cases settle into spherical, quasiequilibrium configurations consisting of a cold NS core surrounded by a hot mantle, resembling Thorne-Zytkow objects. Extrapolating our results to realistic WD compactions, we predict that the likely outcome of a head-on collision of a realistic, massive WDNS system will be the formation of a quasiequilibrium Thorne-Zytkow-like object.

  5. Venus atmosphere simulated by a high-resolution general circulation model

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko

    2016-07-01

    An atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) have been developed (e.g., Sugimoto et al., 2014a) and a very high-resolution simulation is performed. The highest resolution of the model is T319L120; 960 times 480 horizontal grids (grid intervals are about 40 km) with 120 vertical layers (layer intervals are about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal and semi-diurnal components. The infrared radiative process is simplified by adopting Newtonian cooling approximation. The temperature is relaxed to a prescribed horizontally uniform temperature distribution, in which a layer with almost neutral static stability observed in the Venus atmosphere presents. A fast zonal wind in a solid-body rotation is given as the initial state. Starting from this idealized superrotation, the model atmosphere reaches a quasi-equilibrium state within 1 Earth year and this state is stably maintained for more than 10 Earth years. The zonal-mean zonal flow with weak midlatitude jets has almost constant velocity of 120 m/s in latitudes between 45°S and 45°N at the cloud top levels, which agrees very well with observations. In the cloud layer, baroclinic waves develop continuously at midlatitudes and generate Rossby-type waves at the cloud top (Sugimoto et al., 2014b). At the polar region, warm polar vortex zonally surrounded by a cold latitude band (cold collar) is well reproduced (Ando et al., 2016). As for horizontal kinetic energy spectra, divergent component is broadly (k>10) larger than rotational component compared with that on Earth (Kashimura et al., in preparation). Finally, recent results for thermal tides and small-scale waves will be shown in the presentation. Sugimoto, N. et al. (2014a), Baroclinic modes in the Venus atmosphere simulated by GCM, Journal of Geophysical Research: Planets, Vol. 119, p1950-1968. Sugimoto, N. et al. (2014b), Waves in a Venus general

  6. Examining the Accuracy of Astrophysical Disk Simulations with a Generalized Hydrodynamical Test Problem

    NASA Astrophysics Data System (ADS)

    Raskin, Cody; Owen, J. Michael

    2016-11-01

    We discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extension of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.

  7. Simulations of the general circulation of the Martian atmosphere. II - Seasonal pressure variations

    NASA Astrophysics Data System (ADS)

    Pollack, J. B.; Haberle, R. M.; Murphy, J. R.; Schaeffer, J.; Lee, H.

    1993-02-01

    The CO2 seasonal cycle of the Martian atmosphere and surface is simulated with a hybrid energy balance model that incorporates dynamical and radiation information from a large number of general circulation model runs. This information includes: heating due to atmospheric heat advection, the seasonally varying ratio of the surface pressure at the two Viking landing sites to the globally averaged pressure, the rate of CO2 condensation in the atmosphere, and solar heating of the atmosphere and surface. The predictions of the energy balance model are compared with the seasonal pressure variations measured at the two Viking landing sites and the springtime retreat of the seasonal polar cap boundaries. The following quantities are found to have a strong influence on the seasonal pressures at the Viking landing sites: albedo of the seasonal CO2 ice deposits, emissivity of this deposit, atmospheric heat advection, and the pressure ratio.

  8. Real time simulation of nonlinear generalized predictive control for wind energy conversion system with nonlinear observer.

    PubMed

    Ouari, Kamel; Rekioua, Toufik; Ouhrouche, Mohand

    2014-01-01

    In order to make a wind power generation truly cost-effective and reliable, an advanced control techniques must be used. In this paper, we develop a new control strategy, using nonlinear generalized predictive control (NGPC) approach, for DFIG-based wind turbine. The proposed control law is based on two points: NGPC-based torque-current control loop generating the rotor reference voltage and NGPC-based speed control loop that provides the torque reference. In order to enhance the robustness of the controller, a disturbance observer is designed to estimate the aerodynamic torque which is considered as an unknown perturbation. Finally, a real-time simulation is carried out to illustrate the performance of the proposed controller.

  9. Simulating incompressible flow on moving meshfree grids using General Finite Differences (GFD)

    NASA Astrophysics Data System (ADS)

    Vasyliv, Yaroslav; Alexeev, Alexander

    2016-11-01

    We simulate incompressible flow around an oscillating cylinder at different Reynolds numbers using General Finite Differences (GFD) on a meshfree grid. We evolve the meshfree grid by treating each grid node as a particle. To compute velocities and accelerations, we consider the particles at a particular instance as Eulerian observation points. The incompressible Navier-Stokes equations are directly discretized using GFD with boundary conditions enforced using a sharp interface treatment. Cloud sizes are set such that the local approximations use only 16 neighbors. To enforce incompressibility, we apply a semi-implicit approximate projection method. To prevent overlapping particles and formation of voids in the grid, we propose a particle regularization scheme based on a local minimization principle. We validate the GFD results for an oscillating cylinder against the lattice Boltzmann method and find good agreement. Financial support provided by National Science Foundation (NSF) Graduate Research Fellowship, Grant No. DGE-1148903.

  10. Finite-difference simulation and visualization of elastodynamics in time-evolving generalized curvilinear coordinates

    NASA Technical Reports Server (NTRS)

    Kaul, Upender K. (Inventor)

    2009-01-01

    Modeling and simulation of free and forced structural vibrations is essential to an overall structural health monitoring capability. In the various embodiments, a first principles finite-difference approach is adopted in modeling a structural subsystem such as a mechanical gear by solving elastodynamic equations in generalized curvilinear coordinates. Such a capability to generate a dynamic structural response is widely applicable in a variety of structural health monitoring systems. This capability (1) will lead to an understanding of the dynamic behavior of a structural system and hence its improved design, (2) will generate a sufficiently large space of normal and damage solutions that can be used by machine learning algorithms to detect anomalous system behavior and achieve a system design optimization and (3) will lead to an optimal sensor placement strategy, based on the identification of local stress maxima all over the domain.

  11. Fully implicit mixed-hybrid finite-element discretization for general purpose subsurface reservoir simulation

    NASA Astrophysics Data System (ADS)

    Abushaikha, Ahmad S.; Voskov, Denis V.; Tchelepi, Hamdi A.

    2017-10-01

    We present a new fully-implicit, mixed-hybrid, finite-element (MHFE) discretization scheme for general-purpose compositional reservoir simulation. The locally conservative scheme solves the coupled momentum and mass balance equations simultaneously, and the fluid system is modeled using a cubic equation-of-state. We introduce a new conservative flux approach for the mass balance equations for this fully-implicit approach. We discuss the nonlinear solution procedure for the proposed approach, and we present extensive numerical tests to demonstrate the convergence and accuracy of the MHFE method using tetrahedral elements. We also compare the method to other advanced discretization schemes for unstructured meshes and tensor permeability. Finally, we illustrate the applicability and robustness of the method for highly heterogeneous reservoirs with unstructured grids.

  12. Simulation of the planetary boundary layer with the UCLA general circulation model

    NASA Technical Reports Server (NTRS)

    Suarez, M. J.; Arakawa, A.; Randall, D. A.

    1981-01-01

    A planetary boundary layer (PBL) model is presented which employs a mixed layer entrainment formulation to describe the mass exchange between the mixed layer with the upper, laminar atmosphere. A modified coordinate system couples the mixed layer model with large scale and sub-grid scale processes of a general circulation model. The vertical coordinate is configured as a sigma coordinate with the lower boundary, the top of the PBL, and the prescribed pressure level near the tropopause expressed as coordinate surfaces. The entrainment mass flux is parameterized by assuming the dissipation rate of turbulent kinetic energy to be proportional to the positive part of the generation by convection or mechanical production. The results of a simulation of July are presented for the entire globe.

  13. Strong scaling of general-purpose molecular dynamics simulations on GPUs

    NASA Astrophysics Data System (ADS)

    Glaser, Jens; Nguyen, Trung Dac; Anderson, Joshua A.; Lui, Pak; Spiga, Filippo; Millan, Jaime A.; Morse, David C.; Glotzer, Sharon C.

    2015-07-01

    We describe a highly optimized implementation of MPI domain decomposition in a GPU-enabled, general-purpose molecular dynamics code, HOOMD-blue (Anderson and Glotzer, 2013). Our approach is inspired by a traditional CPU-based code, LAMMPS (Plimpton, 1995), but is implemented within a code that was designed for execution on GPUs from the start (Anderson et al., 2008). The software supports short-ranged pair force and bond force fields and achieves optimal GPU performance using an autotuning algorithm. We are able to demonstrate equivalent or superior scaling on up to 3375 GPUs in Lennard-Jones and dissipative particle dynamics (DPD) simulations of up to 108 million particles. GPUDirect RDMA capabilities in recent GPU generations provide better performance in full double precision calculations. For a representative polymer physics application, HOOMD-blue 1.0 provides an effective GPU vs. CPU node speed-up of 12.5 ×.

  14. Intraseasonal eddies in the Sulawesi Sea simulated in an ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Masumoto, Y.; Kagimoto, T.; Yoshida, M.; Fukuda, M.; Hirose, N.; Yamagata, T.

    The intraseasonal variability associated with mesoscale eddies in the Sulawesi Sea simulated in a high resolution ocean general circulation model is described in detail. The cyclonic eddies, with a diameter of about 400 km, are generated at the entrance of the Sulawesi Sea between the Mindanao and the Halmahera Islands with 40 days interval. They are associated with a high speed (> 20 cm/s) down to 1000 m level. The anticlockwise circulation in the Sulawesi Sea, reported so far in both models and observations, may be a long time-averaged image of the above energetic eddies. The intraseasonal eddies significantly affect the volume transport through passages in the northern part of the Indonesian archipelago. The intraseasonal transport variation, however, is highly damped within the Indonesian seas in the present model.

  15. Reconstruction of bremsstrahlung spectra from attenuation data using generalized simulated annealing.

    PubMed

    Menin, O H; Martinez, A S; Costa, A M

    2016-05-01

    A generalized simulated annealing algorithm, combined with a suitable smoothing regularization function is used to solve the inverse problem of X-ray spectrum reconstruction from attenuation data. The approach is to set the initial acceptance and visitation temperatures and to standardize the terms of objective function to automate the algorithm to accommodate different spectra ranges. Experiments with both numerical and measured attenuation data are presented. Results show that the algorithm reconstructs spectra shapes accurately. It should be noted that in this algorithm, the regularization function was formulated to guarantee a smooth spectrum, thus, the presented technique does not apply to X-ray spectrum where characteristic radiation are present. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Comparing four approaches to generalized redirected walking: simulation and live user data.

    PubMed

    Hodgson, Eric; Bachmann, Eric

    2013-04-01

    Redirected walking algorithms imperceptibly rotate a virtual scene and scale movements to guide users of immersive virtual environment systems away from tracking area boundaries. These distortions ideally permit users to explore large and potentially unbounded virtual worlds while walking naturally through a physically limited space. Estimates of the physical space required to perform effective redirected walking have been based largely on the ability of humans to perceive the distortions introduced by redirected walking and have not examined the impact the overall steering strategy used. This work compares four generalized redirected walking algorithms, including Steer-to-Center, Steer-to-Orbit, Steer-to-Multiple-Targets and Steer-to-Multiple+Center. Two experiments are presented based on simulated navigation as well as live-user navigation carried out in a large immersive virtual environment facility. Simulations were conducted with both synthetic paths and previously-logged user data. Primary comparison metrics include mean and maximum distances from the tracking area center for each algorithm, number of wall contacts, and mean rates of redirection. Results indicated that Steer-to-Center out-performed all other algorithms relative to these metrics. Steer-to-Orbit also performed well in some circumstances.

  17. Evaluating Parameterizations in General Circulation Models: Climate Simulation Meets Weather Prediction

    SciTech Connect

    Phillips, T J; Potter, G L; Williamson, D L; Cederwall, R T; Boyle, J S; Fiorino, M; Hnilo, J J; Olson, J G; Xie, S; Yio, J J

    2004-05-06

    To significantly improve the simulation of climate by general circulation models (GCMs), systematic errors in representations of relevant processes must first be identified, and then reduced. This endeavor demands that the GCM parameterizations of unresolved processes, in particular, should be tested over a wide range of time scales, not just in climate simulations. Thus, a numerical weather prediction (NWP) methodology for evaluating model parameterizations and gaining insights into their behavior may prove useful, provided that suitable adaptations are made for implementation in climate GCMs. This method entails the generation of short-range weather forecasts by a realistically initialized climate GCM, and the application of six-hourly NWP analyses and observations of parameterized variables to evaluate these forecasts. The behavior of the parameterizations in such a weather-forecasting framework can provide insights on how these schemes might be improved, and modified parameterizations then can be tested in the same framework. In order to further this method for evaluating and analyzing parameterizations in climate GCMs, the U.S. Department of Energy is funding a joint venture of its Climate Change Prediction Program (CCPP) and Atmospheric Radiation Measurement (ARM) Program: the CCPP-ARM Parameterization Testbed (CAPT). This article elaborates the scientific rationale for CAPT, discusses technical aspects of its methodology, and presents examples of its implementation in a representative climate GCM.

  18. General Relativistic Magnetohydrodynamic Simulations of Binary Neutron Star Mergers with the APR4 Equation of State

    NASA Astrophysics Data System (ADS)

    Endrizzi, Andrea; Ciolfi, Riccardo; Giacomazzo, Bruno; Kastaun, Wolfgang; Kawamura, Takumu

    2016-03-01

    We present new results of fully general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) mergers performed with the Whisky code. All the models use a piecewise polytropic approximation of the APR4 equation of state (EOS) for cold matter, together with a ''hybrid'' part to incorporate thermal effects during the evolution. We consider both equal and unequal-mass models, with total masses such that either a supramassive NS or a black hole (BH) is formed after merger. Each model is evolved with and without a magnetic field initially confined to the stellar interior. We present the different gravitational wave (GW) signals as well as a detailed description of the matter dynamics (magnetic field evolution, ejected mass, post-merger remnant properties, disk mass). Our new simulations provide a further important step in the understanding of these GW sources and their possible connection with the engine of short gamma-ray bursts (both in the ``standard'' and in the ``time-reversal'' scenarios) and with other electromagnetic counterparts.

  19. General relativistic magnetohydrodynamic simulations of binary neutron star mergers with the APR4 equation of state

    NASA Astrophysics Data System (ADS)

    Endrizzi, A.; Ciolfi, R.; Giacomazzo, B.; Kastaun, W.; Kawamura, T.

    2016-08-01

    We present new results of fully general relativistic magnetohydrodynamic simulations of binary neutron star (BNS) mergers performed with the Whisky code. All the models use a piecewise polytropic approximation of the APR4 equation of state for cold matter, together with a ‘hybrid’ part to incorporate thermal effects during the evolution. We consider both equal and unequal-mass models, with total masses such that either a supramassive NS or a black hole is formed after merger. Each model is evolved with and without a magnetic field initially confined to the stellar interior. We present the different gravitational wave (GW) signals as well as a detailed description of the matter dynamics (magnetic field evolution, ejected mass, post-merger remnant/disk properties). Our simulations provide new insights into BNS mergers, the associated GW emission and the possible connection with the engine of short gamma-ray bursts (both in the ‘standard’ and in the ‘time-reversal’ scenarios) and other electromagnetic counterparts.

  20. A general method for spatially coarse-graining Metropolis Monte Carlo simulations onto a lattice.

    PubMed

    Liu, Xiao; Seider, Warren D; Sinno, Talid

    2013-03-21

    A recently introduced method for coarse-graining standard continuous Metropolis Monte Carlo simulations of atomic or molecular fluids onto a rigid lattice of variable scale [X. Liu, W. D. Seider, and T. Sinno, Phys. Rev. E 86, 026708 (2012)] is further analyzed and extended. The coarse-grained Metropolis Monte Carlo technique is demonstrated to be highly consistent with the underlying full-resolution problem using a series of detailed comparisons, including vapor-liquid equilibrium phase envelopes and spatial density distributions for the Lennard-Jones argon and simple point charge water models. In addition, the principal computational bottleneck associated with computing a coarse-grained interaction function for evolving particle positions on the discretized domain is addressed by the introduction of new closure approximations. In particular, it is shown that the coarse-grained potential, which is generally a function of temperature and coarse-graining level, can be computed at multiple temperatures and scales using a single set of free energy calculations. The computational performance of the method relative to standard Monte Carlo simulation is also discussed.

  1. General Relativistic Simulations of Low-Mass Magnetized Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Giacomazzo, Bruno

    2017-01-01

    We will present general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) systems that produce long-lived neutron stars (NSs) after merger. While the standard scenario for short gamma-ray bursts (SGRBs) requires the formation after merger of a spinning black hole surrounded by an accretion disk, other theoretical models, such as the time-reversal scenario, predict the formation of a long-lived magnetar. The formation of a long-lived magnetar could in particular explain the X-ray plateaus that have been observed in some SGRBs. Moreover, observations of NSs with masses of 2 solar masses indicate that the equation of state of NS matter should support masses larger than that. Therefore a significant fraction of BNS mergers will produce long-lived NSs. This has important consequences both on the emission of gravitational wave signals and on their electromagnetic counterparts. We will discuss GRMHD simulations of ``low-mass'' magnetized BNS systems with different equations of state and mass ratios. We will describe the properties of their post-merger remnants and of their gravitational and electromagnetic emission.

  2. Optimization of a general-purpose, actively scanned proton beamline for ocular treatments: Geant4 simulations.

    PubMed

    Piersimoni, Pierluigi; Rimoldi, Adele; Riccardi, Cristina; Pirola, Michele; Molinelli, Silvia; Ciocca, Mario

    2015-03-08

    The Italian National Center for Hadrontherapy (CNAO, Centro Nazionale di Adroterapia Oncologica), a synchrotron-based hospital facility, started the treatment of patients within selected clinical trials in late 2011 and 2012 with actively scanned proton and carbon ion beams, respectively. The activation of a new clinical protocol for the irradiation of uveal melanoma using the existing general-purpose proton beamline is foreseen for late 2014. Beam characteristics and patient treatment setup need to be tuned to meet the specific requirements for such a type of treatment technique. The aim of this study is to optimize the CNAO transport beamline by adding passive components and minimizing air gap to achieve the optimal conditions for ocular tumor irradiation. The CNAO setup with the active and passive components along the transport beamline, as well as a human eye-modeled detector also including a realistic target volume, were simulated using the Monte Carlo Geant4 toolkit. The strong reduction of the air gap between the nozzle and patient skin, as well as the insertion of a range shifter plus a patient-specific brass collimator at a short distance from the eye, were found to be effective tools to be implemented. In perspective, this simulation toolkit could also be used as a benchmark for future developments and testing purposes on commercial treatment planning systems.

  3. General relativistic simulations of black-hole-neutron-star mergers: Effects of magnetic fields

    NASA Astrophysics Data System (ADS)

    Etienne, Zachariah B.; Liu, Yuk Tung; Paschalidis, Vasileios; Shapiro, Stuart L.

    2012-03-01

    As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at the end of a black-hole-neutron-star (BHNS) binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these magnetic fields may impact the gravitational waveforms, merger evolution and mass of the remnant disk. Formation of highly-collimated magnetic field lines in the disk+spinning BH remnant may launch relativistic jets, providing the engine for a short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic BHNS simulations from inspiral through merger and disk formation. Different initial magnetic field configurations and strengths are chosen for the NS interior for both nonspinning and moderately spinning (aBH/MBH=0.75) BHs aligned with the orbital angular momentum. Only strong interior (Bmax⁡˜1017G) initial magnetic fields in the NS significantly influence merger dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning and spinning BH cases, respectively. However, detecting the imprint of even a strong magnetic field may be challenging for Advanced LIGO. Though there is no evidence of mass outflows or magnetic field collimation during the preliminary simulations we have performed, higher resolution, coupled with longer disk evolutions and different initial magnetic field configurations, may be required to definitively assess the possibility of BHNS binaries as short-hard gamma-ray burst progenitors.

  4. General Force-Field Parametrization Scheme for Molecular Dynamics Simulations of Conjugated Materials in Solution

    PubMed Central

    2016-01-01

    We describe a general scheme to obtain force-field parameters for classical molecular dynamics simulations of conjugated polymers. We identify a computationally inexpensive methodology for calculation of accurate intermonomer dihedral potentials and partial charges. Our findings indicate that the use of a two-step methodology of geometry optimization and single-point energy calculations using DFT methods produces potentials which compare favorably to high level theory calculation. We also report the effects of varying the conjugated backbone length and alkyl side-chain lengths on the dihedral profiles and partial charge distributions and determine the existence of converged lengths above which convergence is achieved in the force-field parameter sets. We thus determine which calculations are required for accurate parametrization and the scope of a given parameter set for variations to a given molecule. We perform simulations of long oligomers of dioctylfluorene and hexylthiophene in explicit solvent and find peristence lengths and end-length distributions consistent with experimental values. PMID:27397762

  5. Secondary-structure preferences of force fields for proteins evaluated by generalized-ensemble simulations

    NASA Astrophysics Data System (ADS)

    Yoda, Takao; Sugita, Yuji; Okamoto, Yuko

    2004-12-01

    Secondary-structure forming tendencies are examined for six well-known protein force fields: AMBER94, AMBER96, AMBER99, CHARMM22, OPLS-AA/L, and GROMOS96. We performed generalized-ensemble molecular dynamics simulations of two peptides. One of these peptides is C-peptide of ribonuclease A, and the other is the C-terminal fragment from the B1 domain of streptococcal protein G. The former is known to form α-helix structure and the latter β-hairpin structure by experiments. The simulation results revealed significant differences of the secondary-structure forming tendencies among the force fields. Of the six force fields, the results of AMBER99 and CHARMM22 were in accord with experiments for C-peptide. For G-peptide, on the other hand, the results of OPLS-AA/L and GROMOS96 were most consistent with experiments. Therefore, further improvements on the force fields are necessary for studying the protein folding problem from the first principles, in which a single force field can be used for all cases.

  6. Application of the general thermal field model to simulate the behaviour of nanoscale Cu field emitters

    SciTech Connect

    Eimre, Kristjan; Aabloo, Alvo; Parviainen, Stefan Djurabekova, Flyura; Zadin, Vahur

    2015-07-21

    Strong field electron emission from a nanoscale tip can cause a temperature rise at the tip apex due to Joule heating. This becomes particularly important when the current value grows rapidly, as in the pre-breakdown (the electrostatic discharge) condition, which may occur near metal surfaces operating under high electric fields. The high temperatures introduce uncertainties in calculations of the current values when using the Fowler–Nordheim equation, since the thermionic component in such conditions cannot be neglected. In this paper, we analyze the field electron emission currents as the function of the applied electric field, given by both the conventional Fowler–Nordheim field emission and the recently developed generalized thermal field emission formalisms. We also compare the results in two limits: discrete (atomistic simulations) and continuum (finite element calculations). The discrepancies of both implementations and their effect on final results are discussed. In both approaches, the electric field, electron emission currents, and Joule heating processes are simulated concurrently and self-consistently. We show that the conventional Fowler–Nordheim equation results in significant underestimation of electron emission currents. We also show that Fowler–Nordheim plots used to estimate the field enhancement factor may lead to significant overestimation of this parameter especially in the range of relatively low electric fields.

  7. Large-eddy simulation of airflow and heat transfer in a general ward of hospital

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Farhad; Himika, Taasnim Ahmed; Molla, Md. Mamun

    2016-07-01

    In this paper, a very popular alternative computational technique, the Lattice Boltzmann Method (LBM) has been used for Large-Eddy Simulation (LES) of airflow and heat transfer in general ward of hospital. Different Reynolds numbers have been used to study the airflow pattern. In LES, Smagorinsky turbulence model has been considered and a discussion has been conducted in brief. A code validation has been performed comparing the present results with benchmark results for lid-driven cavity problem and the results are found to agree very well. LBM is demonstrated through simulation in forced convection inside hospital ward with six beds with a partition in the middle, which acted like a wall. Changes in average rate of heat transfer in terms of average Nusselt numbers have also been recorded in tabular format and necessary comparison has been showed. It was found that partition narrowed the path for airflow and once the air overcame this barrier, it got free space and turbulence appeared. For higher turbulence, the average rate of heat transfer increased and patients near the turbulence zone released maximum heat and felt more comfortable.

  8. TOUGH2: A general-purpose numerical simulator for multiphase nonisothermal flows

    SciTech Connect

    Pruess, K.

    1991-06-01

    Numerical simulators for multiphase fluid and heat flows in permeable media have been under development at Lawrence Berkeley Laboratory for more than 10 yr. Real geofluids contain noncondensible gases and dissolved solids in addition to water, and the desire to model such `compositional` systems led to the development of a flexible multicomponent, multiphase simulation architecture known as MULKOM. The design of MULKOM was based on the recognition that the mass-and energy-balance equations for multiphase fluid and heat flows in multicomponent systems have the same mathematical form, regardless of the number and nature of fluid components and phases present. Application of MULKOM to different fluid mixtures, such as water and air, or water, oil, and gas, is possible by means of appropriate `equation-of-state` (EOS) modules, which provide all thermophysical and transport parameters of the fluid mixture and the permeable medium as a function of a suitable set of primary thermodynamic variables. Investigations of thermal and hydrologic effects from emplacement of heat-generating nuclear wastes into partially water-saturated formations prompted the development and release of a specialized version of MULKOM for nonisothermal flow of water and air, named TOUGH. TOUGH is an acronym for `transport of unsaturated groundwater and heat` and is also an allusion to the tuff formations at Yucca Mountain, Nevada. The TOUGH2 code is intended to supersede TOUGH. It offers all the capabilities of TOUGH and includes a considerably more general subset of MULKOM modules with added capabilities. The paper briefly describes the simulation methodology and user features.

  9. Evaluation of a Mineral Dust Simulation in the Atmospheric-Chemistry General Circulation Model-EMAC

    NASA Astrophysics Data System (ADS)

    Abdel Kader, M.; Astitha, M.; Lelieveld, J.

    2012-04-01

    This study presents an evaluation of the atmospheric mineral dust cycle in the Atmospheric Chemistry General Circulation Model (AC-GCM) using new developed dust emissions scheme. The dust cycle, as an integral part of the Earth System, plays an important role in the Earth's energy balance by both direct and indirect ways. As an aerosol, it significantly impacts the absorption and scattering of radiation in the atmosphere and can modify the optical properties of clouds and snow/ice surfaces. In addition, dust contributes to a range of physical, chemical and bio-geological processes that interact with the cycles of carbon and water. While our knowledge of the dust cycle, its impacts and interactions with the other global-scale bio-geochemical cycles has greatly advanced in the last decades, large uncertainties and knowledge gaps still exist. Improving the dust simulation in global models is essential to minimize the uncertainties in the model results related to dust. In this study, the results are based on the ECHAM5 Modular Earth Submodel System (MESSy) AC-GCM simulations using T106L31 spectral resolution (about 120km ) with 31 vertical levels. The GMXe aerosol submodel is used to simulate the phase changes of the dust particles between soluble and insoluble modes. Dust emission, transport and deposition (wet and dry) are calculated on-line along with the meteorological parameters in every model time step. The preliminary evaluation of the dust concentration and deposition are presented based on ground observations from various campaigns as well as the evaluation of the optical properties of dust using AERONET and satellite (MODIS and MISR) observations. Preliminarily results show good agreement with observations for dust deposition and optical properties. In addition, the global dust emissions, load, deposition and lifetime is in good agreement with the published results. Also, the uncertainties in the dust cycle that contribute to the overall model performance

  10. Using Simulations of Black Holes to Study General Relativity and the Properties of Inner Accretion Flow

    NASA Astrophysics Data System (ADS)

    Hoormann, Janie Katherine

    2016-06-01

    While Albert Einstein's theory of General Relativity (GR) has been tested extensively in our solar system, it is just beginning to be tested in the strong gravitational fields that surround black holes. As a way to study the behavior of gravity in these extreme environments, I have used and added to a ray-tracing code that simulates the X-ray emission from the accretion disks surrounding black holes. In particular, the observational channels which can be simulated include the thermal and reflected spectra, polarization, and reverberation signatures. These calculations can be performed assuming GR as well as four alternative spacetimes. These results can be used to see if it is possible to determine if observations can test the No-Hair theorem of GR which states that stationary, astrophysical black holes are only described by their mass and spin. Although it proves difficult to distinguish between theories of gravity, it is possible to exclude a large portion of the possible deviations from GR using observations of rapidly spinning stellar mass black holes such as Cygnus X-1. The ray-tracing simulations can furthermore be used to study the inner regions of black hole accretion flows. I examined the dependence of X-ray reverberation observations on the ionization of the disk photosphere. My results show that X-ray reverberation and X-ray polarization provides a powerful tool to constrain the geometry of accretion disks which are too small to be imaged directly. The second part of my thesis describes the work on the balloon-borne X-Calibur hard X-ray polarimetry mission and on the space-borne PolSTAR polarimeter concept.

  11. Internal versus SST-forced atmospheric variability as simulated by an atmospheric general circulation model

    SciTech Connect

    Harzallah, A.; Sadourny, R.

    1995-03-01

    The variability of atmospheric flow is analyzed by separating it into an internal part due to atmospheric dynamics only and an external (or forced) part due to the variability of sea surface temperature forcing. The two modes of variability are identified by performing an ensemble of seven independent long-term simulations of the atmospheric response to observed SST (1970-1988) with the LMD atmospheric general circulation model. The forced variability is defined from the analysis of the ensemble mean and the internal variability from the analysis of deviations from the ensemble mean. Emphasis is put on interannual variability of sea level pressure and 500-hPa geopotential height for the Northern Hemisphere winter. In view of the large systematic errors related to the relatively small number of realizations, unbiased variance estimators have been developed. Although statistical significance is not reached in some extratropical regions, large significant extratropical responses are found at the North Pacific-Alaska sector for SLP and over western Canada and the Aleutians for 500-hPa geopotential height. The influence of SST variations on internal variability is also examined by using a 7-year simulation using the climatological SST seasonal cycle. It is found that interannual SST changes strongly influence the geographical distribution of internal variability; in particular, it tends to increase it over oceans. EOF decompositions, showing that the model realistically simulates the leading observed variability modes. The geographical structure of internal variability patterns is found to be similar to that of total variability, although similar modes tend to evolve rather differently in time. The zonally symmetric seesaw dominates the internal variability for both observed and climatologically prescribed SST. 46 refs., 15 figs., 3 tabs.

  12. Construction and employment of a low cost laparoscopic simulator. Test on General Surgery residents.

    PubMed

    Del Rio, Paolo; Musini, Luca; Iapichino, Gioacchino; Arcuri, Maria Francesca; Nisi, Pier Cosimo; Sianesi, Mario

    2015-01-01

    Based on studies that confirm the usefulness of simulators in laparoscopic surgical training, we designed and tested a cost-effective solution to improve the skills of surgeons training in the operating room. The goal was to exercise the basic gestures of laparoscopic surgery. The initial budget of € 500 was sufficient for this project. We spent only € 360 on the majority of the components, which included buying a laptop. The project was performed with material that was readily available online, and the assembly did not require special tools. The goal was to make the product easily replicable. The test was performed using a simulator on 9 doctors in specialist training in general surgery at the University Hospital of Parma distributed, who were equally distributed among the six years of school in general surgery. The first exercise, which was the simplest, had as its objective the acquisition of familiarity with the vision monocular feature of VL and coordination between the two hands. We observed statistically significant improvement between the first and second (2.52 to 2.17 min, p = 0.006) tests and between the first and third (from 2.52 to 1.57 min, p = 0.001) tests with a non-significant correlation between the time of year and the achieved specialty. In the second exercise, there was a statistically significant improvement due to the excessive excursion of the confidence intervals (remarkable variability with overlap of the same features). This exercise, which consisted of two parts, explored the ability to use two hands independently. The third and final exercise involved the packaging of a laparoscopic ligation and was the most complex because it required skill in the use of instruments with both hands as well as considerable coordination. The t-test for paired data showed a significant improvement in all tests with p = 0.0008 between the average time for the first and second tests, p = 0.001 between the second and third tests, and p = 0.01 between the

  13. General Fluid System Simulation Program to Model Secondary Flows in Turbomachinery

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok K.; Van Hoosier, Katherine P.

    1995-01-01

    The complexity and variety of turbomachinery flow circuits created a need for a general fluid system simulation program for test data anomaly resolution as well as design review. The objective of the paper is to present a computer program that has been developed to support Marshall Space Flight Center's turbomachinery internal flow analysis efforts. The computer program solves for the mass. energy and species conservation equation at each node and flow rate equation at each branch of the network by a novel numerical procedure which is a combination of both Newton-Ralphson and successive substitution method and uses a thermodynamic property program for computing real gas properties. A generalized, robust, modular, and 'user-friendly' computer program has been developed to model internal flow rates, pressures, temperatures, concentrations of gas mixtures and axial thrusts. The program can be used for any network for compressible and incompressible flows, choked flow, change of phase and gaseous mixturecs. The code has been validated by comparing the predictions with Space Shuttle Main Engine test data.

  14. GENERAL RELATIVISTIC SIMULATIONS OF MAGNETIZED PLASMAS AROUND MERGING SUPERMASSIVE BLACK HOLES

    SciTech Connect

    Giacomazzo, Bruno; Baker, John G.; Van Meter, James R.; Coleman Miller, M.; Reynolds, Christopher S.

    2012-06-10

    Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this Letter, we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular, we observe a total amplification of the magnetic field of {approx}2 orders of magnitude, which is driven by the accretion onto the binary and that leads to much stronger electromagnetic signals, more than a factor of 10{sup 4} larger than comparable calculations done in the force-free regime where such amplifications are not possible.

  15. Simulating Titan's Atmosphere Using the TitanWRF and Titan MITgcm General Circulation Models

    NASA Astrophysics Data System (ADS)

    Newman, C. E.; Lian, Y.; Lee, C.; Richardson, M. I.

    2011-12-01

    We have developed two 3D Titan general circulation models (GCMs): TitanWRF, based on NCAR's WRF model [Newman et al., 2011], and a Titan version of the MITgcm [Adcroft et al., 2004]. We will present and compare the stratospheric superrotation and tropospheric methane cycle produced using these GCMs, and compare results with observations. Original TitanWRF simulations were unable to produce significant stratospheric superrotation, however we later found that simulations performed without any explicitly imposed sub-grid-scale horizontal diffusion were able to reproduce far greater latitudinal temperature gradients and superrotation (see Figure), similar in many respects to that observed [e.g., Flasar et al., 2005; Achterberg et al., 2011]. Diagnostics show that equatorial superrotation is generated during episodic angular momentum 'transfer events' during model spin-up, and maintained by similar (yet shorter) events once the model has reached steady state. We suggest that these transfer events are produced by barotropic waves, generated at low latitudes then propagating poleward through a critical layer, thus accelerating low latitudes while decelerating the mid-to-high latitude jet in the late fall through early spring hemisphere. We will present these and more recent results from the Titan MITgcm, examining the waves and mechanisms driving superrotation in both models, and discussing the importance of both implicit and explicit horizontal diffusion on model stability and superrotation. We have also used both GCMs to examine Titan's tropospheric methane cycle: parameterizing surface evaporation of methane according to boundary layer humidity, wind speed and atmospheric stability; using a simple parameterization of cloud formation and precipitation; including latent heat effects; and allowing surface regions to be depleted of methane if evaporation exceeds precipitation over time. We will present and compare simulations of cloud locations and timings with those

  16. A Multi-mission Event-Driven Component-Based System for Support of Flight Software Development, ATLO, and Operations first used by the Mars Science Laboratory (MSL) Project

    NASA Technical Reports Server (NTRS)

    Dehghani, Navid; Tankenson, Michael

    2006-01-01

    This viewgraph presentation reviews the architectural description of the Mission Data Processing and Control System (MPCS). MPCS is an event-driven, multi-mission ground data processing components providing uplink, downlink, and data management capabilities which will support the Mars Science Laboratory (MSL) project as its first target mission. MPCS is designed with these factors (1) Enabling plug and play architecture (2) MPCS has strong inheritance from GDS components that have been developed for other Flight Projects (MER, MRO, DAWN, MSAP), and are currently being used in operations and ATLO, and (3) MPCS components are Java-based, platform independent, and are designed to consume and produce XML-formatted data

  17. The generalized Onsager model and DSMC simulations of high-speed rotating flows with product and waste baffles

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev

    2016-10-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer in a high-speed rotating cylinder, are extended to a multiply connected domain, created by the product and waste baffles. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. An explicit expression for the baffle stream function is obtained using the boundary layer solutions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement between the analysis and simulations, to within 15%, provided the wall-slip in both the flow velocity and temperature are incorporated in the analytical solutions.

  18. The generalized Onsager model and DSMC simulations of high-speed rotating flows with product and waste baffles

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2017-01-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer in a high-speed rotating cylinder, are extended to a multiply connected domain, created by the product and waste baffles. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. An explicit expression for the baffle stream function is obtained using the boundary layer solutions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement between the analysis and simulations, to within 15%, provided the wall-slip in both the flow velocity and temperature are incorporated in the analytical solutions.

  19. The generalized Onsager model and DSMC simulations of high-speed rotating flows with product and waste baffles

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2016-11-01

    The generalized Onsager model for the radial boundary layer and of the generalized Carrier-Maslen model for the axial boundary layer in a high-speed rotating cylinder, are extended to a multiply connected domain, created by the product and waste baffles. For a single component gas, the analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier-Maslen equation for the velocity potential. In both cases, the equations are linearized in the perturbation to the base flow, which is a solid-body rotation. An explicit expression for the baffle stream function is obtained using the boundary layer solutions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement between the analysis and simulations, to within 15%, provided the wall-slip in both the flow velocity and temperature are incorporated in the analytical solutions.

  20. General-relativistic magnetohydrodynamics simulations of black hole accretion disks: Dynamics and radiative properties

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka

    The goal of the series of studies in this thesis is to understand the black hole accretion process and predict its observational properties. The highly non-linear process involves a turbulent magnetized plasma in a general relativistic regime, thus making it hard to study analytically. We use numerical simulations, specifically general relativistic magnetohydrodynamics (GRMHD), to construct a realistic dynamical and radiation model of accretion disks. Our simulations are for black holes in low luminous regimes that probably possesses a hot and thick accretion disk. Flows in this regime are called radiatively inefficient accretion flows (RIAF). The most plausible mechanism for transporting angular momentum is turbulence induced by magnetorotational instability (MRI). The RIAF model has been used to model the supermassive black hole at the center of our Milky Way galaxy, Sagittarius A* (Sgr A*). Owing to its proximity, rich observational data of Sgr A* is available to compare with the simulation results. We focus mainly on four topics. First, we analyse numerical convergence of 3D GRMHD global disk simulations. Convergence is one of the essential factors in deciding quantitative outcomes of the simulations. We analyzed dimensionless shell-averaged quantities such as plasma beta, the azimuthal correlation length (angle) of fluid variables, and spectra of the source for four different resolutions. We found that all the variables converged with the highest resolution (384x384x256 in radial, poloidal, and azimuthal directions) except the magnetic field correlation length. It probably requires another factor of 2 in resolution to achieve convergence. Second, we studied the effect of equation of state on dynamics of GRMHD simulation and radiative transfer. Temperature of RIAF gas is high, and all the electrons are relativistic, but not the ions. In addition, the dynamical time scale of the accretion disk is shorter than the collisional time scale of electrons and ions

  1. KMCLib: A general framework for lattice kinetic Monte Carlo (KMC) simulations

    NASA Astrophysics Data System (ADS)

    Leetmaa, Mikael; Skorodumova, Natalia V.

    2014-09-01

    KMCLib is a general framework for lattice kinetic Monte Carlo (KMC) simulations. The program can handle simulations of the diffusion and reaction of millions of particles in one, two, or three dimensions, and is designed to be easily extended and customized by the user to allow for the development of complex custom KMC models for specific systems without having to modify the core functionality of the program. Analysis modules and on-the-fly elementary step diffusion rate calculations can be implemented as plugins following a well-defined API. The plugin modules are loosely coupled to the core KMCLib program via the Python scripting language. KMCLib is written as a Python module with a backend C++ library. After initial compilation of the backend library KMCLib is used as a Python module; input to the program is given as a Python script executed using a standard Python interpreter. We give a detailed description of the features and implementation of the code and demonstrate its scaling behavior and parallel performance with a simple one-dimensional A-B-C lattice KMC model and a more complex three-dimensional lattice KMC model of oxygen-vacancy diffusion in a fluorite structured metal oxide. KMCLib can keep track of individual particle movements and includes tools for mean square displacement analysis, and is therefore particularly well suited for studying diffusion processes at surfaces and in solids. Catalogue identifier: AESZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AESZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 49 064 No. of bytes in distributed program, including test data, etc.: 1 575 172 Distribution format: tar.gz Programming language: Python and C++. Computer: Any computer that can run a C++ compiler and a Python interpreter. Operating system: Tested on Ubuntu 12

  2. Studies of molecular docking between fibroblast growth factor and heparin using generalized simulated annealing

    NASA Astrophysics Data System (ADS)

    Pita, Samuel Silva Da Rocha; Fernandes, Tácio Vinício Amorim; Caffarena, Ernesto Raul; Pascutti, Pedro Geraldo

    Since the middle 70s, the main molecular docking problem consists in limitations to treat adequately the degrees of freedom of protein (or a receptor) due to the energy landscape roughness and the high computational cost. Until recently, only few algorithms considering flexible simultaneously both ligand and receptor at low computational cost were developed. As a recent proposed Statistical Mechanics, generalized simulated annealing (GSA) has been employed at diverse works concerning global optimization problems. In this work, we used this method exploring the molecular docking problem taking into account the FGF-2 and heparin complex. Since the requirements of an efficient docking algorithm are accuracy and velocity, we tested the influence of GSA parameters qA (new configuration acceptance index), qV (energy surface visiting index), and qT (temperature decreasing control) on the performance of GSADOCK program. Our simulations showed that as temperature parameter qT increases, qA parameter follows this behavior in the interval ranging from 1.1 to 2.3. We found that the GSA parameters have the best performance for the qA values ranging from 1.1 to 1.3, qV values from 1.3 to 1.5, and qT values from 1.1 to 1.7. Most of good qV values were equal or next the good qT values. Finally, the implemented algorithm is trustworthy and can be employed as a tool of molecular modeling methods. The final version of the program will be free of charge and will be accessible at our home-page or could be requested to the authors for e-mail.

  3. General relativistic magnetohydrodynamic simulations of binary neutron star mergers forming a long-lived neutron star

    NASA Astrophysics Data System (ADS)

    Ciolfi, Riccardo; Kastaun, Wolfgang; Giacomazzo, Bruno; Endrizzi, Andrea; Siegel, Daniel M.; Perna, Rosalba

    2017-03-01

    Merging binary neutron stars (BNSs) represent the ultimate targets for multimessenger astronomy, being among the most promising sources of gravitational waves (GWs), and, at the same time, likely accompanied by a variety of electromagnetic counterparts across the entire spectrum, possibly including short gamma-ray bursts (SGRBs) and kilonova/macronova transients. Numerical relativity simulations play a central role in the study of these events. In particular, given the importance of magnetic fields, various aspects of this investigation require general relativistic magnetohydrodynamics (GRMHD). So far, most GRMHD simulations focused the attention on BNS mergers leading to the formation of a hypermassive neutron star (NS), which, in turn, collapses within few tens of ms into a black hole surrounded by an accretion disk. However, recent observations suggest that a significant fraction of these systems could form a long-lived NS remnant, which will either collapse on much longer time scales or remain indefinitely stable. Despite the profound implications for the evolution and the emission properties of the system, a detailed investigation of this alternative evolution channel is still missing. Here, we follow this direction and present a first detailed GRMHD study of BNS mergers forming a long-lived NS. We consider magnetized binaries with different mass ratios and equations of state and analyze the structure of the NS remnants, the rotation profiles, the accretion disks, the evolution and amplification of magnetic fields, and the ejection of matter. Moreover, we discuss the connection with the central engine of SGRBs and provide order-of-magnitude estimates for the kilonova/macronova signal. Finally, we study the GW emission, with particular attention to the post-merger phase.

  4. A general mixture model and its application to coastal sandbar migration simulation

    NASA Astrophysics Data System (ADS)

    Liang, Lixin; Yu, Xiping

    2017-04-01

    A mixture model for general description of sediment laden flows is developed and then applied to coastal sandbar migration simulation. Firstly the mixture model is derived based on the Eulerian-Eulerian approach of the complete two-phase flow theory. The basic equations of the model include the mass and momentum conservation equations for the water-sediment mixture and the continuity equation for sediment concentration. The turbulent motion of the mixture is formulated for the fluid and the particles respectively. A modified k-ɛ model is used to describe the fluid turbulence while an algebraic model is adopted for the particles. A general formulation for the relative velocity between the two phases in sediment laden flows, which is derived by manipulating the momentum equations of the enhanced two-phase flow model, is incorporated into the mixture model. A finite difference method based on SMAC scheme is utilized for numerical solutions. The model is validated by suspended sediment motion in steady open channel flows, both in equilibrium and non-equilibrium state, and in oscillatory flows as well. The computed sediment concentrations, horizontal velocity and turbulence kinetic energy of the mixture are all shown to be in good agreement with experimental data. The mixture model is then applied to the study of sediment suspension and sandbar migration in surf zones under a vertical 2D framework. The VOF method for the description of water-air free surface and topography reaction model is coupled. The bed load transport rate and suspended load entrainment rate are all decided by the sea bed shear stress, which is obtained from the boundary layer resolved mixture model. The simulation results indicated that, under small amplitude regular waves, erosion occurred on the sandbar slope against the wave propagation direction, while deposition dominated on the slope towards wave propagation, indicating an onshore migration tendency. The computation results also shows that

  5. Simulation and Prediction of Tropical Intraseasonal Variability with Contemporary General Circulation Model

    NASA Astrophysics Data System (ADS)

    Fu, J. X.

    2008-12-01

    Tropical Intra-Seasonal Variability (TISV) is a fundamental mode of tropical climate. The associated intraseasonal wet and dry spells strongly modulate the weather systems (e.g., TC), thus the socio-economic activities (e.g., agriculture, water management et al.) around the globe. To develop a capability in forecasting TISV with lead time beyond two weeks is extremely desirable. Unfortunately, many state-of-the-art general circulation models (GCMs) still have various problems to reasonably simulate TISV. Under real forecast context (e.g., Seo et al., 2005), the predictability of TISV is only about a week by simply extending conventional weather forecast with longer integration. This study aims to address two relevant questions: 1) what are the critical pieces of model physics for the realistic simulation of TISV that have been missed or misrepresented in many contemporary GCMs? 2) In what degree is the TISV predictability affected by different settings of initial and boundary conditions? To address the first question, a suite of sensitivity experiments has been carried out under a weather forecast mode and with three 20-year free integrations with ECHAM-4 and a coupled version. It was found that a robust TISV can be sustained in the model only when the model produces a significant proportion (˜ 30%) of stratiform rainfall for both the forecast experiments and long-term free integrations. When the stratiform rainfall proportion becomes small, the tropical rainfall in the model is dominated by high-frequency disturbances with neither eastward propagating nor northward-propagating TISV being sustained. This result suggests that the representation of stratiform rainfall and its connections with convective component in contemporary GCMs is probably a critical issue needed to be seriously reconsidered, in order to have overall success in the simulation and prediction of TISV. To address the second question, a series of TISV forecast experiments has been conducted under

  6. Assessment of Atmosphere-Ocean General Circulation Model Simulations of Winter Northern Hemisphere Atmospheric Blocking

    NASA Astrophysics Data System (ADS)

    Vial, Jessica; Osborn, Tim

    2010-05-01

    Characterized by their persistence and quasi-stationary features, large-scale atmospheric blocking are often responsible for extreme weather events, which can have enormous impacts on human life, economy and environment e.g. European heat wave in summer 2003. Therefore, diagnostics of the present-day climate and future projections of potential changes in blocking-related extreme events are essential for risk management and adaptation planning. This study focuses on assessing the ability of six coupled Atmosphere-Ocean General Circulation Models (AOGCMs) to simulate large-scale winter atmospheric blocking in the Northern Hemisphere for the present-day climate (1957-1999). A modified version of the Tibaldi and Molteni (1990)'s blocking index, which measures the strength of the average westerly flow in the mid-latitudes, is applied to daily averaged 500 hPa geopotential height output from the climate models. ERA-40 re-analysis atmospheric data have also been used over the same time period to verify the models' results. The two preferred regions of blocking development, in the Euro-Atlantic and North Pacific, are well captured by most of the models. However, the prominent error in blocking simulations, according to a number of previous model assessments, consists of an underestimation of the total frequency of blocking episodes over both regions. A more detailed analysis of blocking frequency as a function of duration revealed that this error was due to an insufficient number of medium spells and long-lasting episodes, and a shift in blocking lifetime distributions towards shorter blocks, while short-lived blocking events (between 5 and 8 days) tend to be overestimated. The impact of models' systematic errors on blocking simulations has been analyzed, and results suggest that there is a primary need to reduce the time-mean bias to improve the representation of blocking in climate models. The underestimated high-frequency variability of the transient eddies embedded in

  7. Sleep promotes consolidation and generalization of extinction learning in simulated exposure therapy for spider fear.

    PubMed

    Pace-Schott, Edward F; Verga, Patrick W; Bennett, Tobias S; Spencer, Rebecca M C

    2012-08-01

    Simulated exposure therapy for spider phobia served as a clinically naturalistic model to study effects of sleep on extinction. Spider-fearing, young adult women (N = 66), instrumented for skin conductance response (SCR), heart rate acceleration (HRA) and corrugator electromyography (EMG), viewed 14 identical 1-min videos of a behaving spider before a 12-hr delay containing a normal night's Sleep (N = 20) or continuous daytime Wake (N = 23), or a 2-hr delay of continuous wake in the Morning (N = 11) or Evening (N = 12). Following the delay, all groups viewed this same video 6 times followed by six 1-min videos of a novel spider. After each video, participants rated disgust, fearfulness and unpleasantness. In all 4 groups, all measures except corrugator EMG diminished across Session 1 (extinction learning) and, excepting SCR to a sudden noise, increased from the old to novel spider in Session 2. In Wake only, summed subjective ratings and SCR to the old spider significantly increased across the delay (extinction loss) and were greater for the novel vs. the old spider when it was equally novel at the beginning of Session 1 (sensitization). In Sleep only, SCR to a sudden noise decreased across the inter-session delay (extinction augmentation) and, along with HRA, was lower to the novel spider than initially to the old spider in Session 1 (extinction generalization). None of the above differentiated Morning and Evening groups suggesting that intervening sleep, rather than time-of-testing, produced differences between Sleep and Wake. Thus, sleep following exposure therapy may promote retention and generalization of extinction learning.

  8. Wind driven general circulation of the Mediterranean Sea simulated with a Spectral Element Ocean Model

    NASA Astrophysics Data System (ADS)

    Molcard, A.; Pinardi, N.; Iskandarani, M.; Haidvogel, D. B.

    2002-05-01

    This work is an attempt to simulate the Mediterranean Sea general circulation with a Spectral Finite Element Model. This numerical technique associates the geometrical flexibility of the finite elements for the proper coastline definition with the precision offered by spectral methods. The model is reduced gravity and we study the wind-driven ocean response in order to explain the large scale sub-basin gyres and their variability. The study period goes from January 1987 to December 1993 and two forcing data sets are used. The effect of wind variability in space and time is analyzed and the relationship between wind stress curl and ocean response is stressed. Some of the main permanent structures of the general circulation (Gulf of Lions cyclonic gyre, Rhodes gyre, Gulf of Syrte anticylone) are shown to be induced by permanent wind stress curl structures. The magnitude and spatial variability of the wind is important in determining the appearance or disappearance of some gyres (Tyrrhenian anticyclonic gyre, Balearic anticyclonic gyre, Ionian cyclonic gyre). An EOF analysis of the seasonal variability indicates that the weakening and strengthening of the Levantine basin boundary currents is a major component of the seasonal cycle in the basin. The important discovery is that seasonal and interannual variability peak at the same spatial scales in the ocean response and that the interannual variability includes the change in amplitude and phase of the seasonal cycle in the sub-basin scale gyres and boundary currents. The Coriolis term in the vorticity balance seems to be responsible for the weakening of anticyclonic structures and their total disappearance when they are close to a boundary. The process of adjustment to winds produces a train of coastally trapped gravity waves which travel around the eastern and western basins, respectively in approximately 6 months. This corresponds to a phase velocity for the wave of about 1 m/s, comparable to an average velocity of

  9. Generalized Scalable Multiple Copy Algorithms for Molecular Dynamics Simulations in NAMD

    PubMed Central

    Jiang, Wei; Phillips, James C.; Huang, Lei; Fajer, Mikolai; Meng, Yilin; Gumbart, James C.; Luo, Yun; Schulten, Klaus; Roux, Benoît

    2014-01-01

    Computational methodologies that couple the dynamical evolution of a set of replicated copies of a system of interest offer powerful and flexible approaches to characterize complex molecular processes. Such multiple copy algorithms (MCAs) can be used to enhance sampling, compute reversible work and free energies, as well as refine transition pathways. Widely used examples of MCAs include temperature and Hamiltonian-tempering replica-exchange molecular dynamics (T-REMD and H-REMD), alchemical free energy perturbation with lambda replica-exchange (FEP/λ-REMD), umbrella sampling with Hamiltonian replica exchange (US/H-REMD), and string method with swarms-of-trajectories conformational transition pathways. Here, we report a robust and general implementation of MCAs for molecular dynamics (MD) simulations in the highly scalable program NAMD built upon the parallel programming system Charm++. Multiple concurrent NAMD instances are launched with internal partitions of Charm++ and located continuously within a single communication world. Messages between NAMD instances are passed by low-level point-to-point communication functions, which are accessible through NAMD’s Tcl scripting interface. The communication-enabled Tcl scripting provides a sustainable application interface for end users to realize generalized MCAs without modifying the source code. Illustrative applications of MCAs with fine-grained inter-copy communication structure, including global lambda exchange in FEP/λ-REMD, window swapping US/H-REMD in multidimensional order parameter space, and string method with swarms-of-trajectories were carried out on IBM Blue Gene/Q to demonstrate the versatility and massive scalability of the present implementation. PMID:24944348

  10. Sleep Promotes Consolidation and Generalization of Extinction Learning in Simulated Exposure Therapy for Spider Fear

    PubMed Central

    Pace-Schott, Edward F.; Verga, Patrick; Bennet, Tobias; Spencer, Rebecca M.C.

    2012-01-01

    Simulated exposure therapy for spider phobia served as a clinically naturalistic model to study effects of sleep on extinction. Spider-fearing, young adult women (N=66), instrumented for skin conductance response (SCR), heart rate acceleration (HRA) and corrugator electromyography (EMG), viewed 14 identical 1-min videos of a behaving spider before a 12-hr delay containing a normal night’s Sleep (N=20) or continuous daytime Wake (N=23), or a 2-hr delay of continuous wake in the Morning (N=11) or Evening (N=12). Following the delay, all groups viewed this same video 6 times followed by six 1-min videos of a novel spider. After each video, participants rated disgust, fearfulness and unpleasantness. In all 4 groups, all measures except corrugator EMG diminished across Session 1 (extinction learning) and, excepting SCR to a sudden noise, increased from the old to novel spider in Session 2. In Wake only, summed subjective ratings and SCR to the old spider significantly increased across the delay (extinction loss) and were greater for the novel vs. the old spider when it was equally novel at the beginning of Session 1 (sensitization). In Sleep only, SCR to a sudden noise decreased across the inter-session delay (extinction augmentation) and, along with HRA, was lower to the novel spider than initially to the old spider in Session 1 (extinction generalization). None of the above differentiated Morning and Evening groups suggesting that intervening sleep, rather than time-of-testing, produced differences between Sleep and Wake. Thus, sleep following exposure therapy may promote retention and generalization of extinction learning. PMID:22578824

  11. Numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses.

    PubMed

    Sarifuddin; Chakravarty, S; Mandal, P K; Layek, G C

    2008-01-01

    An updated numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses is developed. A shear-thinning fluid modelling the deformation dependent viscosity of blood is considered for the characterization of generalized Newtonian behaviour of blood. The arterial model is treated as two-dimensional and axisymmetric with an outline of the stenosis obtained from a three-dimensional casting of a mildly stenosed artery. The full Navier-Stokes equations governing blood flow are written in the dimensionless form and the solution is accomplished by finite time-step advancement through their finite difference staggered grid representations. The marker and cell (MAC) method comprising the use of a set of marker particles moving with the fluid is used for the purpose. Results are obtained for three differently shaped stenoses - irregular, smooth and cosine curve representations. The present results do agree well with those of existing investigations in the steady state, but contrary to their conclusions the present findings demonstrate that the excess pressure drop across the cosine and the smooth stenoses is caused by neither their smoothness nor their higher degree of symmetry relative to the irregular stenosis, but is rather an effect of area cover with respect to the irregular stenosis. This effect clearly prevails throughout the entire physiological range of Reynolds numbers. Further the in-depth study in flow patterns reveals the development of flow separation zones in the diverging part of the stenosis towards the arterial wall, and they are influenced by non-Newtonian blood rheology, distensibility of the wall and flow unsteadiness in order to validate the applicability of the present model.

  12. Barriers to the implementation and uptake of simulation-based training programs in general surgery: a multinational qualitative study.

    PubMed

    Hosny, Shady G; Johnston, Maximilian J; Pucher, Philip H; Erridge, Simon; Darzi, Ara

    2017-08-24

    Despite evidence demonstrating the advantages of simulation training in general surgery, it is not widely integrated into surgical training programs worldwide. The aim of this study was to identify barriers and facilitators to the implementation and uptake of surgical simulation training programs. A multinational qualitative study was conducted using semi-structured interviews of general surgical residents and experts. Each interview was audio recorded, transcribed verbatim, and underwent emergent theme analysis. All data were anonymized and results pooled. A total of 37 individuals participated in the study. Seventeen experts (Program Directors and Surgical Attendings with an interest in surgical education) and 20 residents drawn from the United States, Canada, United Kingdom, France, and Japan were interviewed. Barriers to simulation-based training were identified based on key themes including financial cost, access, and translational benefit. Participants described cost (89%) and access (76%) as principal barriers to uptake. Common facilitators included a mandatory requirement to complete simulation training (78%) and on-going assessment of skills (78%). Participants felt that simulation training could improve patient outcomes (76%) but identified a lack of evidence to demonstrate benefit (38%). There was a consensus that simulation training has not been widely implemented (70%). There are multiple barriers to the implementation of surgical simulation training programs, however, there is agreement that these programs could potentially improve patient outcomes. Identifying these barriers enable the targeted use of facilitators to deliver simulation training programs. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Merger of white dwarf-neutron star binaries: Prelude to hydrodynamic simulations in general relativity

    SciTech Connect

    Paschalidis, Vasileios; MacLeod, Morgan; Baumgarte, Thomas W.; Shapiro, Stuart L.

    2009-07-15

    White dwarf-neutron star binaries generate detectable gravitational radiation. We construct Newtonian equilibrium models of corotational white dwarf-neutron star (WDNS) binaries in circular orbit and find that these models terminate at the Roche limit. At this point the binary will undergo either stable mass transfer (SMT) and evolve on a secular time scale, or unstable mass transfer (UMT), which results in the tidal disruption of the WD. The path a given binary will follow depends primarily on its mass ratio. We analyze the fate of known WDNS binaries and use population synthesis results to estimate the number of LISA-resolved galactic binaries that will undergo either SMT or UMT. We model the quasistationary SMT epoch by solving a set of simple ordinary differential equations and compute the corresponding gravitational waveforms. Finally, we discuss in general terms the possible fate of binaries that undergo UMT and construct approximate Newtonian equilibrium configurations of merged WDNS remnants. We use these configurations to assess plausible outcomes of our future, fully relativistic simulations of these systems. If sufficient WD debris lands on the NS, the remnant may collapse, whereby the gravitational waves from the inspiral, merger, and collapse phases will sweep from LISA through LIGO frequency bands. If the debris forms a disk about the NS, it may fragment and form planets.

  14. Global General Relativistic Magnetohydrodynamic Simulations of Black Hole Accretion Flows: A Convergence Study

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka; Dolence, Joshua C.; Gammie, Charles F.; Noble, Scott C.

    2012-01-01

    Global, general relativistic magnetohydrodynamic (GRMHD) simulations of non-radiative, magnetized disks are widely used to model accreting black holes. We have performed a convergence study of GRMHD models computed with HARM3D. The models span a factor of four in linear resolution, from 96 × 96 × 64 to 384 × 384 × 256. We consider three diagnostics of convergence: (1) dimensionless shell-averaged quantities such as plasma β (2) the azimuthal correlation length of fluid variables; and (3) synthetic spectra of the source including synchrotron emission, absorption, and Compton scattering. Shell-averaged temperature is, except for the lowest resolution run, nearly independent of resolution; shell-averaged plasma β decreases steadily with resolution but shows signs of convergence. The azimuthal correlation lengths of density, internal energy, and temperature decrease steadily with resolution but show signs of convergence. In contrast, the azimuthal correlation length of magnetic field decreases nearly linearly with grid size. We argue by analogy with local models, however, that convergence should be achieved with another factor of two in resolution. Synthetic spectra are, except for the lowest resolution run, nearly independent of resolution. The convergence behavior is consistent with that of higher physical resolution local model ("shearing box") calculations and with the recent non-relativistic global convergence studies of Hawley et al.

  15. Theoretical analysis and simulations of the generalized Lotka-Volterra model.

    PubMed

    Malcai, Ofer; Biham, Ofer; Richmond, Peter; Solomon, Sorin

    2002-09-01

    The dynamics of generalized Lotka-Volterra systems is studied by theoretical techniques and computer simulations. These systems describe the time evolution of the wealth distribution of individuals in a society, as well as of the market values of firms in the stock market. The individual wealths or market values are given by a set of time dependent variables w(i), i=1,...,N. The equations include a stochastic autocatalytic term (representing investments), a drift term (representing social security payments), and a time dependent saturation term (due to the finite size of the economy). The w(i)'s turn out to exhibit a power-law distribution of the form P(w) approximately w(-1-alpha). It is shown analytically that the exponent alpha can be expressed as a function of one parameter, which is the ratio between the constant drift component (social security) and the fluctuating component (investments). This result provides a link between the lower and upper cutoffs of this distribution, namely, between the resources available to the poorest and those available to the richest in a given society. The value of alpha is found to be insensitive to variations in the saturation term, which represent the expansion or contraction of the economy. The results are of much relevance to empirical studies that show that the distribution of the individual wealth in different countries during different periods in the 20th century has followed a power-law distribution with 1

  16. GENERAL RELATIVISTIC SIMULATIONS OF ACCRETION INDUCED COLLAPSE OF NEUTRON STARS TO BLACK HOLES

    SciTech Connect

    Giacomazzo, Bruno; Perna, Rosalba

    2012-10-10

    Neutron stars (NSs) in the astrophysical universe are often surrounded by accretion disks. Accretion of matter onto an NS may increase its mass above the maximum value allowed by its equation of state, inducing its collapse to a black hole (BH). Here we study this process for the first time, in three-dimensions, and in full general relativity. By considering three initial NS configurations, each with and without a surrounding disk (of mass {approx}7% M{sub NS}), we investigate the effect of the accretion disk on the dynamics of the collapse and its imprint on both the gravitational wave (GW) and electromagnetic (EM) signals that can be emitted by these sources. We show in particular that, even if the GW signal is similar for the accretion induced collapse (AIC) and the collapse of an NS in vacuum (and detectable only for Galactic sources), the EM counterpart could allow us to discriminate between these two types of events. In fact, our simulations show that, while the collapse of an NS in vacuum leaves no appreciable baryonic matter outside the event horizon, an AIC is followed by a phase of rapid accretion of the surviving disk onto the newly formed BH. The post-collapse accretion rates, on the order of {approx}10{sup -2} M{sub Sun} s{sup -1}, make these events tantalizing candidates as engines of short gamma-ray bursts.

  17. Merger of white dwarf-neutron star binaries: Prelude to hydrodynamic simulations in general relativity

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; MacLeod, Morgan; Baumgarte, Thomas W.; Shapiro, Stuart L.

    2009-07-01

    White dwarf-neutron star binaries generate detectable gravitational radiation. We construct Newtonian equilibrium models of corotational white dwarf-neutron star (WDNS) binaries in circular orbit and find that these models terminate at the Roche limit. At this point the binary will undergo either stable mass transfer (SMT) and evolve on a secular time scale, or unstable mass transfer (UMT), which results in the tidal disruption of the WD. The path a given binary will follow depends primarily on its mass ratio. We analyze the fate of known WDNS binaries and use population synthesis results to estimate the number of LISA-resolved galactic binaries that will undergo either SMT or UMT. We model the quasistationary SMT epoch by solving a set of simple ordinary differential equations and compute the corresponding gravitational waveforms. Finally, we discuss in general terms the possible fate of binaries that undergo UMT and construct approximate Newtonian equilibrium configurations of merged WDNS remnants. We use these configurations to assess plausible outcomes of our future, fully relativistic simulations of these systems. If sufficient WD debris lands on the NS, the remnant may collapse, whereby the gravitational waves from the inspiral, merger, and collapse phases will sweep from LISA through LIGO frequency bands. If the debris forms a disk about the NS, it may fragment and form planets.

  18. A General Hybrid Radiation Transport Scheme for Star Formation Simulations on an Adaptive Grid

    NASA Astrophysics Data System (ADS)

    Klassen, Mikhail; Kuiper, Rolf; Pudritz, Ralph E.; Peters, Thomas; Banerjee, Robi; Buntemeyer, Lars

    2014-12-01

    Radiation feedback plays a crucial role in the process of star formation. In order to simulate the thermodynamic evolution of disks, filaments, and the molecular gas surrounding clusters of young stars, we require an efficient and accurate method for solving the radiation transfer problem. We describe the implementation of a hybrid radiation transport scheme in the adaptive grid-based FLASH general magnetohydrodyanmics code. The hybrid scheme splits the radiative transport problem into a raytracing step and a diffusion step. The raytracer captures the first absorption event, as stars irradiate their environments, while the evolution of the diffuse component of the radiation field is handled by a flux-limited diffusion solver. We demonstrate the accuracy of our method through a variety of benchmark tests including the irradiation of a static disk, subcritical and supercritical radiative shocks, and thermal energy equilibration. We also demonstrate the capability of our method for casting shadows and calculating gas and dust temperatures in the presence of multiple stellar sources. Our method enables radiation-hydrodynamic studies of young stellar objects, protostellar disks, and clustered star formation in magnetized, filamentary environments.

  19. Stationary eddies in the Mars general circulation as simulated by the NASA-Ames GCM

    NASA Technical Reports Server (NTRS)

    Barnes, J. R.; Pollack, J. B.; Haberle, Robert M.

    1993-01-01

    Quasistationary eddies are prominent in a large set of simulations of the Mars general circulation performed with the NASA-Ames GCM. Various spacecraft observations have at least hinted at the existence of such eddies in the Mars atmosphere. The GCM stationary eddies appear to be forced primarily by the large Mars topography, and (to a much lesser degree) by spatial variations in the surface albedo and thermal inertia. The stationary eddy circulations exhibit largest amplitudes at high altitudes (above 30-40 km) in the winter extratropical regions. In these regions they are of planetary scale, characterized largely by zonal wavenumbers 1 and 2. Southern Hemisphere winter appears to be dominated by a very strong wave 1 pattern, with both waves 1 and 2 being prominent in the Northern Hemisphere winter regime. This difference seems to be basically understandable in terms of differences in the topography in the two hemispheres. The stationary eddies in the northern winter extratropics are found to increase in amplitude with dust loading. This behavior appears to be at least partly associated with changes in the structure of the zonal-mean flow that favor a greater response to wave 1 topographic forcing. There are also strong stationary eddy circulations in the tropics and in the summer hemisphere. The eddies in the summer subtropics and extratropics arc substantially stronger in southern summer than in northern summer. The summer hemisphere stationary circulations are relatively shallow and are characterized by smaller zonal scales than those in the winter extratropics.

  20. A general hybrid radiation transport scheme for star formation simulations on an adaptive grid

    SciTech Connect

    Klassen, Mikhail; Pudritz, Ralph E.; Kuiper, Rolf; Peters, Thomas; Banerjee, Robi; Buntemeyer, Lars

    2014-12-10

    Radiation feedback plays a crucial role in the process of star formation. In order to simulate the thermodynamic evolution of disks, filaments, and the molecular gas surrounding clusters of young stars, we require an efficient and accurate method for solving the radiation transfer problem. We describe the implementation of a hybrid radiation transport scheme in the adaptive grid-based FLASH general magnetohydrodyanmics code. The hybrid scheme splits the radiative transport problem into a raytracing step and a diffusion step. The raytracer captures the first absorption event, as stars irradiate their environments, while the evolution of the diffuse component of the radiation field is handled by a flux-limited diffusion solver. We demonstrate the accuracy of our method through a variety of benchmark tests including the irradiation of a static disk, subcritical and supercritical radiative shocks, and thermal energy equilibration. We also demonstrate the capability of our method for casting shadows and calculating gas and dust temperatures in the presence of multiple stellar sources. Our method enables radiation-hydrodynamic studies of young stellar objects, protostellar disks, and clustered star formation in magnetized, filamentary environments.

  1. GLOBAL GENERAL RELATIVISTIC MAGNETOHYDRODYNAMIC SIMULATIONS OF BLACK HOLE ACCRETION FLOWS: A CONVERGENCE STUDY

    SciTech Connect

    Shiokawa, Hotaka; Dolence, Joshua C.; Gammie, Charles F.; Noble, Scott C.

    2012-01-10

    Global, general relativistic magnetohydrodynamic (GRMHD) simulations of non-radiative, magnetized disks are widely used to model accreting black holes. We have performed a convergence study of GRMHD models computed with HARM3D. The models span a factor of four in linear resolution, from 96 Multiplication-Sign 96 Multiplication-Sign 64 to 384 Multiplication-Sign 384 Multiplication-Sign 256. We consider three diagnostics of convergence: (1) dimensionless shell-averaged quantities such as plasma {beta}; (2) the azimuthal correlation length of fluid variables; and (3) synthetic spectra of the source including synchrotron emission, absorption, and Compton scattering. Shell-averaged temperature is, except for the lowest resolution run, nearly independent of resolution; shell-averaged plasma {beta} decreases steadily with resolution but shows signs of convergence. The azimuthal correlation lengths of density, internal energy, and temperature decrease steadily with resolution but show signs of convergence. In contrast, the azimuthal correlation length of magnetic field decreases nearly linearly with grid size. We argue by analogy with local models, however, that convergence should be achieved with another factor of two in resolution. Synthetic spectra are, except for the lowest resolution run, nearly independent of resolution. The convergence behavior is consistent with that of higher physical resolution local model ({sup s}hearing box{sup )} calculations and with the recent non-relativistic global convergence studies of Hawley et al.

  2. Simulating the Generalized Gibbs Ensemble (GGE): A Hilbert space Monte Carlo approach

    NASA Astrophysics Data System (ADS)

    Alba, Vincenzo

    By combining classical Monte Carlo and Bethe ansatz techniques we devise a numerical method to construct the Truncated Generalized Gibbs Ensemble (TGGE) for the spin-1/2 isotropic Heisenberg (XXX) chain. The key idea is to sample the Hilbert space of the model with the appropriate GGE probability measure. The method can be extended to other integrable systems, such as the Lieb-Liniger model. We benchmark the approach focusing on GGE expectation values of several local observables. As finite-size effects decay exponentially with system size, moderately large chains are sufficient to extract thermodynamic quantities. The Monte Carlo results are in agreement with both the Thermodynamic Bethe Ansatz (TBA) and the Quantum Transfer Matrix approach (QTM). Remarkably, it is possible to extract in a simple way the steady-state Bethe-Gaudin-Takahashi (BGT) roots distributions, which encode complete information about the GGE expectation values in the thermodynamic limit. Finally, it is straightforward to simulate extensions of the GGE, in which, besides the local integral of motion (local charges), one includes arbitrary functions of the BGT roots. As an example, we include in the GGE the first non-trivial quasi-local integral of motion.

  3. Hidden Conformation Events in DNA Base Extrusions: A Generalized Ensemble Path Optimization and Equilibrium Simulation Study

    PubMed Central

    Cao, Liaoran; Lv, Chao; Yang, Wei

    2013-01-01

    DNA base extrusion is a crucial component of many biomolecular processes. Elucidating how bases are selectively extruded from the interiors of double-strand DNAs is pivotal to accurately understanding and efficiently sampling this general type of conformational transitions. In this work, the on-the-path random walk (OTPRW) method, which is the first generalized ensemble sampling scheme designed for finite-temperature-string path optimizations, was improved and applied to obtain the minimum free energy path (MFEP) and the free energy profile of a classical B-DNA major-groove base extrusion pathway. Along the MFEP, an intermediate state and the corresponding transition state were located and characterized. The MFEP result suggests that a base-plane-elongation event rather than the commonly focused base-flipping event is dominant in the transition state formation portion of the pathway; and the energetic penalty at the transition state is mainly introduced by the stretching of the Watson-Crick base pair. Moreover to facilitate the essential base-plane-elongation dynamics, the surrounding environment of the flipped base needs to be intimately involved. Further taking the advantage of the extended-dynamics nature of the OTPRW Hamiltonian, an equilibrium generalized ensemble simulation was performed along the optimized path; and based on the collected samples, several base-flipping (opening) angle collective variables were evaluated. In consistence with the MFEP result, the collective variable analysis result reveals that none of these commonly employed flipping (opening) angles alone can adequately represent the base extrusion pathway, especially in the pre-transition-state portion. As further revealed by the collective variable analysis, the base-pairing partner of the extrusion target undergoes a series of in-plane rotations to facilitate the base-plane-elongation dynamics. A base-plane rotation angle is identified to be a possible reaction coordinate to represent

  4. Parallelized computation for computer simulation of electrocardiograms using personal computers with multi-core CPU and general-purpose GPU.

    PubMed

    Shen, Wenfeng; Wei, Daming; Xu, Weimin; Zhu, Xin; Yuan, Shizhong

    2010-10-01

    Biological computations like electrocardiological modelling and simulation usually require high-performance computing environments. This paper introduces an implementation of parallel computation for computer simulation of electrocardiograms (ECGs) in a personal computer environment with an Intel CPU of Core (TM) 2 Quad Q6600 and a GPU of Geforce 8800GT, with software support by OpenMP and CUDA. It was tested in three parallelization device setups: (a) a four-core CPU without a general-purpose GPU, (b) a general-purpose GPU plus 1 core of CPU, and (c) a four-core CPU plus a general-purpose GPU. To effectively take advantage of a multi-core CPU and a general-purpose GPU, an algorithm based on load-prediction dynamic scheduling was developed and applied to setting (c). In the simulation with 1600 time steps, the speedup of the parallel computation as compared to the serial computation was 3.9 in setting (a), 16.8 in setting (b), and 20.0 in setting (c). This study demonstrates that a current PC with a multi-core CPU and a general-purpose GPU provides a good environment for parallel computations in biological modelling and simulation studies. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

  5. A generalized Ising model for studying alloy evolution under irradiation and its use in kinetic Monte Carlo simulations.

    PubMed

    Huang, Chen-Hsi; Marian, Jaime

    2016-10-26

    We derive an Ising Hamiltonian for kinetic simulations involving interstitial and vacancy defects in binary alloys. Our model, which we term 'ABVI', incorporates solute transport by both interstitial defects and vacancies into a mathematically-consistent framework, and thus represents a generalization to the widely-used ABV model for alloy evolution simulations. The Hamiltonian captures the three possible interstitial configurations in a binary alloy: A-A, A-B, and B-B, which makes it particularly useful for irradiation damage simulations. All the constants of the Hamiltonian are expressed in terms of bond energies that can be computed using first-principles calculations. We implement our ABVI model in kinetic Monte Carlo simulations and perform a verification exercise by comparing our results to published irradiation damage simulations in simple binary systems with Frenkel pair defect production and several microstructural scenarios, with matching agreement found.

  6. A generalized Ising model for studying alloy evolution under irradiation and its use in kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Huang, Chen-Hsi; Marian, Jaime

    2016-10-01

    We derive an Ising Hamiltonian for kinetic simulations involving interstitial and vacancy defects in binary alloys. Our model, which we term ‘ABVI’, incorporates solute transport by both interstitial defects and vacancies into a mathematically-consistent framework, and thus represents a generalization to the widely-used ABV model for alloy evolution simulations. The Hamiltonian captures the three possible interstitial configurations in a binary alloy: A-A, A-B, and B-B, which makes it particularly useful for irradiation damage simulations. All the constants of the Hamiltonian are expressed in terms of bond energies that can be computed using first-principles calculations. We implement our ABVI model in kinetic Monte Carlo simulations and perform a verification exercise by comparing our results to published irradiation damage simulations in simple binary systems with Frenkel pair defect production and several microstructural scenarios, with matching agreement found.

  7. Seasonal variation of Titan's atmospheric structure simulated by a general circulation model.

    PubMed

    Tokano, T; Neubauer, F M; Laube, M; McKay, C P

    1999-01-01

    The seasonal variation of Titan's atmospheric structure with emphasis on the stratosphere is simulated by a three-dimensional general circulation model. The model includes the transport of haze particles by the circulation. The likely pattern of meridional circulation is reconstructed by a comparison of simulated and observed haze and temperature distribution. The GCM produces a weak zonal circulation with a small latitudinal temperature gradient, in conflict with observation. The direct reason is found to be the excessive meridional circulation. Under uniformly distributed opacity sources, the model predicts a pair of symmetric Hadley cells near the equinox and a single global cell with the rising branch in the summer hemisphere below about z = 230 km and a thermally indirect cell above the direct cell near the solstice. The interhemispheric circulation transports haze particles from the summer to the winter hemisphere, causing a maximum haze opacity contrast near the solstice and a smaller contrast near the equinox, contrary to observation. On the other, if the GCM is run under modified cooling rate in order to account for the enhancement in nitrites and some hydrocarbons in the northern hemisphere near the vernal equinox, the meridional cell at the equinox becomes a single cell with rising motions in the autumn hemisphere. A more realistic haze opacity distribution can be reproduced at the equinox. However, a pure transport effect (without particle growth by microphysics, etc.) would not be able to cause the observed discontinuity of the global haze opacity distribution at any location. The stratospheric temperature asymmetry can be explained by a combination of asymmetric radiative heating rates and adiabatic heating due to vertical motion within the thermally indirect cell. A seasonal variation of haze particle number density is unlikely to be responsible for this asymmetry. It is likely that a thermally indirect cell covers the upper portion of the main haze

  8. General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

    SciTech Connect

    McKinney, Jonathan C.; Tchekhovskoy, Alexander; Blandford, Roger D.

    2012-04-26

    Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fields. Firstly, for toroidal field models and BHs with high enough |a/M|, coherent large-scale (i.e. >> H) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate transient relativistic jets. Secondly, for poloidal field models, poloidal magnetic flux readily accretes through the disk from large radii and builds-up to a natural saturation point near the BH. While models with |H/R| {approx} 1 and |a/M| {le} 0.5 do not launch jets due to quenching by mass infall, for sufficiently high |a/M| or low |H/R| the polar magnetic field compresses the inflow into a geometrically thin highly non-axisymmetric 'magnetically choked accretion flow' (MCAF) within which the standard linear magneto-rotational instability is suppressed. The condition of a highly-magnetized state over most of the horizon is optimal for the Blandford-Znajek mechanism that generates persistent relativistic jets with and 100% efficiency for |a/M| {approx}> 0.9. A magnetic Rayleigh-Taylor and Kelvin-Helmholtz unstable magnetospheric interface forms between the compressed inflow and bulging jet magnetosphere, which drives a new jet-disk oscillation (JDO) type of quasi-periodic oscillation (QPO) mechanism. The high-frequency QPO has spherical harmonic |m| = 1 mode period of {tau} {approx} 70GM/c{sup 3} for a/M {approx} 0.9 with coherence quality factors Q {approx}> 10. Overall, our models are qualitatively distinct from most prior MHD simulations (typically, |H/R| << 1 and poloidal flux is limited by

  9. Limits to high-speed simulations of spiking neural networks using general-purpose computers.

    PubMed

    Zenke, Friedemann; Gerstner, Wulfram

    2014-01-01

    To understand how the central nervous system performs computations using recurrent neuronal circuitry, simulations have become an indispensable tool for theoretical neuroscience. To study neuronal circuits and their ability to self-organize, increasing attention has been directed toward synaptic plasticity. In particular spike-timing-dependent plasticity (STDP) creates specific demands for simulations of spiking neural networks. On the one hand a high temporal resolution is required to capture the millisecond timescale of typical STDP windows. On the other hand network simulations have to evolve over hours up to days, to capture the timescale of long-term plasticity. To do this efficiently, fast simulation speed is the crucial ingredient rather than large neuron numbers. Using different medium-sized network models consisting of several thousands of neurons and off-the-shelf hardware, we compare the simulation speed of the simulators: Brian, NEST and Neuron as well as our own simulator Auryn. Our results show that real-time simulations of different plastic network models are possible in parallel simulations in which numerical precision is not a primary concern. Even so, the speed-up margin of parallelism is limited and boosting simulation speeds beyond one tenth of real-time is difficult. By profiling simulation code we show that the run times of typical plastic network simulations encounter a hard boundary. This limit is partly due to latencies in the inter-process communications and thus cannot be overcome by increased parallelism. Overall, these results show that to study plasticity in medium-sized spiking neural networks, adequate simulation tools are readily available which run efficiently on small clusters. However, to run simulations substantially faster than real-time, special hardware is a prerequisite.

  10. Limits to high-speed simulations of spiking neural networks using general-purpose computers

    PubMed Central

    Zenke, Friedemann; Gerstner, Wulfram

    2014-01-01

    To understand how the central nervous system performs computations using recurrent neuronal circuitry, simulations have become an indispensable tool for theoretical neuroscience. To study neuronal circuits and their ability to self-organize, increasing attention has been directed toward synaptic plasticity. In particular spike-timing-dependent plasticity (STDP) creates specific demands for simulations of spiking neural networks. On the one hand a high temporal resolution is required to capture the millisecond timescale of typical STDP windows. On the other hand network simulations have to evolve over hours up to days, to capture the timescale of long-term plasticity. To do this efficiently, fast simulation speed is the crucial ingredient rather than large neuron numbers. Using different medium-sized network models consisting of several thousands of neurons and off-the-shelf hardware, we compare the simulation speed of the simulators: Brian, NEST and Neuron as well as our own simulator Auryn. Our results show that real-time simulations of different plastic network models are possible in parallel simulations in which numerical precision is not a primary concern. Even so, the speed-up margin of parallelism is limited and boosting simulation speeds beyond one tenth of real-time is difficult. By profiling simulation code we show that the run times of typical plastic network simulations encounter a hard boundary. This limit is partly due to latencies in the inter-process communications and thus cannot be overcome by increased parallelism. Overall, these results show that to study plasticity in medium-sized spiking neural networks, adequate simulation tools are readily available which run efficiently on small clusters. However, to run simulations substantially faster than real-time, special hardware is a prerequisite. PMID:25309418

  11. Simulating Titan's methane cycle with the TitanWRF General Circulation Model

    NASA Astrophysics Data System (ADS)

    Newman, Claire E.; Richardson, Mark I.; Lian, Yuan; Lee, Christopher

    2016-03-01

    Observations provide increasing evidence of a methane hydrological cycle on Titan. Earth-based and Cassini-based monitoring has produced data on the seasonal variation in cloud activity and location, with clouds being observed at increasingly low latitudes as Titan moved out of southern summer. Lakes are observed at high latitudes, with far larger lakes and greater areal coverage in the northern hemisphere, where some shorelines extend down as far as 50°N. Rainfall at some point in the past is suggested by the pattern of flow features on the surface at the Huygens landing site, while recent rainfall is suggested by surface change. As with the water cycle on Earth, the methane cycle on Titan is both impacted by tropospheric dynamics and likely able to impact this circulation via feedbacks. Here we use the 3D TitanWRF General Circulation Model (GCM) to simulate Titan's methane cycle. In this initial work we use a simple large-scale condensation scheme with latent heat feedbacks and a finite surface reservoir of methane, and focus on large-scale dynamical interactions between the atmospheric circulation and methane, and how these impact seasonal changes and the long term (steady state) behavior of the methane cycle. We note five major conclusions: (1) Condensation and precipitation in the model is sporadic in nature, with interannual variability in its timing and location, but tends to occur in association with both (a) frequent strong polar upwelling during spring and summer in each hemisphere, and (b) the Inter-Tropical Convergence Zone (ITCZ), a region of increased convergence and upwelling due to the seasonally shifting Hadley cells. (2) An active tropospheric methane cycle affects the stratospheric circulation, slightly weakening the stratospheric superrotation produced. (3) Latent heating feedback strongly influences surface and near-surface temperatures, narrowing the latitudinal range of the ITCZ, and changing the distribution - and generally weakening the

  12. FULLY GENERAL RELATIVISTIC SIMULATIONS OF CORE-COLLAPSE SUPERNOVAE WITH AN APPROXIMATE NEUTRINO TRANSPORT

    SciTech Connect

    Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

    2012-08-10

    We present results from the first generation of multi-dimensional hydrodynamic core-collapse simulations in full general relativity (GR) that include an approximate treatment of neutrino transport. Using an M1 closure scheme with an analytic variable Eddington factor, we solve the energy-independent set of radiation energy and momentum based on the Thorne's momentum formalism. Our newly developed code is designed to evolve the Einstein field equation together with the GR radiation hydrodynamic equations. We follow the dynamics starting from the onset of gravitational core collapse of a 15 M{sub Sun} star, through bounce, up to about 100 ms postbounce in this study. By computing four models that differ according to 1D to 3D and by switching from special relativistic (SR) to GR hydrodynamics, we study how the spacial multi-dimensionality and GR would affect the dynamics in the early postbounce phase. Our 3D results support the anticipation in previous 1D results that the neutrino luminosity and average neutrino energy of any neutrino flavor in the postbounce phase increase when switching from SR to GR hydrodynamics. This is because the deeper gravitational well of GR produces more compact core structures, and thus hotter neutrino spheres at smaller radii. By analyzing the residency timescale to the neutrino-heating timescale in the gain region, we show that the criterion to initiate neutrino-driven explosions can be most easily satisfied in 3D models, irrespective of SR or GR hydrodynamics. Our results suggest that the combination of GR and 3D hydrodynamics provides the most favorable condition to drive a robust neutrino-driven explosion.

  13. A Generalized Fluid System Simulation Program to Model Flow Distribution in Fluid Networks

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok; Bailey, John W.; Schallhorn, Paul; Steadman, Todd

    1998-01-01

    This paper describes a general purpose computer program for analyzing steady state and transient flow in a complex network. The program is capable of modeling phase changes, compressibility, mixture thermodynamics and external body forces such as gravity and centrifugal. The program's preprocessor allows the user to interactively develop a fluid network simulation consisting of nodes and branches. Mass, energy and specie conservation equations are solved at the nodes; the momentum conservation equations are solved in the branches. The program contains subroutines for computing "real fluid" thermodynamic and thermophysical properties for 33 fluids. The fluids are: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutane, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride and ammonia. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. Seventeen different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include: pipe flow, flow through a restriction, non-circular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct, labyrinth seal, parallel plates, common fittings and valves, pump characteristics, pump power, valve with a given loss coefficient, and a Joule-Thompson device. The system of equations describing the fluid network is solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods. This paper also illustrates the application and verification of the code by comparison with Hardy Cross method for steady state flow and analytical solution for unsteady flow.

  14. Characterization of Parallelism and Deadlocks in Distributed Digital Logic Simulation

    DTIC Science & Technology

    1988-11-03

    Using these definitions we get: LP was deadlocked by an unevaluated path of n levels, If For each input j where Ij < E7 m and each LPk. where bki=n...Science, August 1988. [161 Andrew Wilson. Paralelization of an Event Driven Simulator on the Encore Multimaz. Technical Report ETR 86-005, Encore Computer

  15. DSIM: A distributed simulator

    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.

  16. Generalized event-chain Monte Carlo: constructing rejection-free global-balance algorithms from infinitesimal steps.

    PubMed

    Michel, Manon; Kapfer, Sebastian C; Krauth, Werner

    2014-02-07

    In this article, we present an event-driven algorithm that generalizes the recent hard-sphere event-chain Monte Carlo method without introducing discretizations in time or in space. A factorization of the Metropolis filter and the concept of infinitesimal Monte Carlo moves are used to design a rejection-free Markov-chain Monte Carlo algorithm for particle systems with arbitrary pairwise interactions. The algorithm breaks detailed balance, but satisfies maximal global balance and performs better than the classic, local Metropolis algorithm in large systems. The new algorithm generates a continuum of samples of the stationary probability density. This allows us to compute the pressure and stress tensor as a byproduct of the simulation without any additional computations.

  17. Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom

    ERIC Educational Resources Information Center

    Clark, Ted M.; Chamberlain, Julia M.

    2014-01-01

    An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six…

  18. Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom

    ERIC Educational Resources Information Center

    Clark, Ted M.; Chamberlain, Julia M.

    2014-01-01

    An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six…

  19. Water properties from first principles: Simulations by a general-purpose quantum mechanical polarizable force field

    PubMed Central

    Donchev, A. G.; Galkin, N. G.; Illarionov, A. A.; Khoruzhii, O. V.; Olevanov, M. A.; Ozrin, V. D.; Subbotin, M. V.; Tarasov, V. I.

    2006-01-01

    We have recently introduced a quantum mechanical polarizable force field (QMPFF) fitted solely to high-level quantum mechanical data for simulations of biomolecular systems. Here, we present an improved form of the force field, QMPFF2, and apply it to simulations of liquid water. The results of the simulations show excellent agreement with a variety of experimental thermodynamic and structural data, as good or better than that provided by specialized water potentials. In particular, QMPFF2 is the only ab initio force field to accurately reproduce the anomalous temperature dependence of water density to our knowledge. The ability of the same force field to successfully simulate the properties of both organic molecules and water suggests it will be useful for simulations of proteins and protein–ligand interactions in the aqueous environment. PMID:16723394

  20. Axisymmetric general relativistic simulations of the accretion-induced collapse of white dwarfs

    SciTech Connect

    Abdikamalov, E. B.; Ott, C. D.; Rezzolla, L.; Dessart, L.; Dimmelmeier, H.; Marek, A.; Janka, H.-T.

    2010-02-15

    The accretion-induced collapse (AIC) of a white dwarf may lead to the formation of a protoneutron star and a collapse-driven supernova explosion. This process represents a path alternative to thermonuclear disruption of accreting white dwarfs in type Ia supernovae. In the AIC scenario, the supernova explosion energy is expected to be small and the resulting transient short-lived, making it hard to detect by electromagnetic means alone. Neutrino and gravitational-wave (GW) observations may provide crucial information necessary to reveal a potential AIC. Motivated by the need for systematic predictions of the GW signature of AIC, we present results from an extensive set of general-relativistic AIC simulations using a microphysical finite-temperature equation of state and an approximate treatment of deleptonization during collapse. Investigating a set of 114 progenitor models in axisymmetric rotational equilibrium, with a wide range of rotational configurations, temperatures and central densities, and resulting white dwarf masses, we extend previous Newtonian studies and find that the GW signal has a generic shape akin to what is known as a 'type III' signal in the literature. Despite this reduction to a single type of waveform, we show that the emitted GWs carry information that can be used to constrain the progenitor and the postbounce rotation. We discuss the detectability of the emitted GWs, showing that the signal-to-noise ratio for current or next-generation interferometer detectors could be high enough to detect such events in our Galaxy. Furthermore, we contrast the GW signals of AIC and rotating massive star iron core collapse and find that they can be distinguished, but only if the distance to the source is known and a detailed reconstruction of the GW time series from detector data is possible. Some of our AIC models form massive quasi-Keplerian accretion disks after bounce. The disk mass is very sensitive to progenitor mass and angular momentum

  1. A general spectral method for the numerical simulation of one-dimensional interacting fermions

    NASA Astrophysics Data System (ADS)

    Clason, Christian; von Winckel, Gregory

    2012-02-01

    This work introduces a general framework for the direct numerical simulation of systems of interacting fermions in one spatial dimension. The approach is based on a specially adapted nodal spectral Galerkin method, where the basis functions are constructed to obey the antisymmetry relations of fermionic wave functions. An efficient MATLAB program for the assembly of the stiffness and potential matrices is presented, which exploits the combinatorial structure of the sparsity pattern arising from this discretization to achieve optimal run-time complexity. This program allows the accurate discretization of systems with multiple fermions subject to arbitrary potentials, e.g., for verifying the accuracy of multi-particle approximations such as Hartree-Fock in the few-particle limit. It can be used for eigenvalue computations or numerical solutions of the time-dependent Schrödinger equation. Program summaryProgram title: assembleFermiMatrix Catalogue identifier: AEKO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 102 No. of bytes in distributed program, including test data, etc.: 2294 Distribution format: tar.gz Programming language: MATLAB Computer: Any architecture supported by MATLAB Operating system: Any supported by MATLAB; tested under Linux (x86-64) and Mac OS X (10.6) RAM: Depends on the data Classification: 4.3, 2.2 Nature of problem: The direct numerical solution of the multi-particle one-dimensional Schrödinger equation in a quantum well is challenging due to the exponential growth in the number of degrees of freedom with increasing particles. Solution method: A nodal spectral Galerkin scheme is used where the basis functions are constructed to obey the antisymmetry relations of the fermionic wave

  2. Accuracy of highly sexually active gay and bisexual men's predictions of their daily likelihood of anal sex and its relevance for intermittent event-driven HIV Pre-Exposure Prophylaxis

    PubMed Central

    Parsons, Jeffrey T.; Rendina, H. Jonathon; Grov, Christian; Ventuneac, Ana; Mustanski, Brian

    2014-01-01

    Objective We sought to examine highly sexually active gay and bisexual men's accuracy in predicting their sexual behavior for the purposes of informing future research on intermittent, event-driven HIV Pre-Exposure Prophylaxis (PrEP). Design For 30 days, 92 HIV-negative men completed a daily survey about their sexual behavior (n = 1,688 days of data) and indicated their likelihood of having anal sex with a casual male partner the following day. Method We utilized multilevel modeling to analyze the association between self-reported likelihood of and subsequent engagement in anal sex. Results We found a linear association between men's reported likelihood of anal sex with casual partners and the actual probability of engaging in sex, though men overestimated the likelihood of sex. Overall, we found that men were better at predicting when they would not have sex than when they would, particularly if any likelihood value greater than 0% was treated as indicative that sex might occur. We found no evidence that men's accuracy of prediction was affected by whether it was a weekend or whether they were using substances, though both did increase the probability of sex. Discussion These results suggested that, were men taking event-driven intermittent PrEP, 14% of doses could have been safely skipped with a minimal rate of false negatives using guidelines of taking a dose unless there was no chance (i.e., 0% likelihood) of sex on the following day. This would result in a savings of over $1,300 per year in medication costs per participant. PMID:25559594

  3. General relativistic corrections to N -body simulations and the Zel'dovich approximation

    NASA Astrophysics Data System (ADS)

    Fidler, Christian; Rampf, Cornelius; Tram, Thomas; Crittenden, Robert; Koyama, Kazuya; Wands, David

    2015-12-01

    The initial conditions for Newtonian N -body simulations are usually generated by applying the Zel'dovich approximation to the initial displacements of the particles using an initial power spectrum of density fluctuations generated by an Einstein-Boltzmann solver. We show that in most gauges the initial displacements generated in this way receive a first-order relativistic correction. We define a new gauge, the N -body gauge, in which this relativistic correction vanishes and show that a conventional Newtonian N -body simulation includes all first-order relativistic contributions (in the absence of radiation) if we identify the coordinates in Newtonian simulations with those in the relativistic N -body gauge.

  4. General order parameter based correlation analysis of protein backbone motions between experimental NMR relaxation measurements and molecular dynamics simulations.

    PubMed

    Liu, Qing; Shi, Chaowei; Yu, Lu; Zhang, Longhua; Xiong, Ying; Tian, Changlin

    2015-02-13

    Internal backbone dynamic motions are essential for different protein functions and occur on a wide range of time scales, from femtoseconds to seconds. Molecular dynamic (MD) simulations and nuclear magnetic resonance (NMR) spin relaxation measurements are valuable tools to gain access to fast (nanosecond) internal motions. However, there exist few reports on correlation analysis between MD and NMR relaxation data. Here, backbone relaxation measurements of (15)N-labeled SH3 (Src homology 3) domain proteins in aqueous buffer were used to generate general order parameters (S(2)) using a model-free approach. Simultaneously, 80 ns MD simulations of SH3 domain proteins in a defined hydrated box at neutral pH were conducted and the general order parameters (S(2)) were derived from the MD trajectory. Correlation analysis using the Gromos force field indicated that S(2) values from NMR relaxation measurements and MD simulations were significantly different. MD simulations were performed on models with different charge states for three histidine residues, and with different water models, which were SPC (simple point charge) water model and SPC/E (extended simple point charge) water model. S(2) parameters from MD simulations with charges for all three histidines and with the SPC/E water model correlated well with S(2) calculated from the experimental NMR relaxation measurements, in a site-specific manner.

  5. Comparisons of observed seasonal climate features with a winter and summer numerical simulation produced with the GLAS general circulation model

    NASA Technical Reports Server (NTRS)

    Halem, M.; Shukla, J.; Mintz, Y.; Wu, M. L.; Godbole, R.; Herman, G.; Sud, Y.

    1979-01-01

    Results are presented from numerical simulations performed with the general circulation model (GCM) for winter and summer. The monthly mean simulated fields for each integration are compared with observed geographical distributions and zonal averages. In general, the simulated sea level pressure and upper level geopotential height field agree well with the observations. Well simulated features are the winter Aleutian and Icelandic lows, the summer southwestern U.S. low, the summer and winter oceanic subtropical highs in both hemispheres, and the summer upper level Tibetan high and Atlantic ridge. The surface and upper air wind fields in the low latitudes are in good agreement with the observations. The geographical distirbutions of the Earth-atmosphere radiation balance and of the precipitation rates over the oceans are well simulated, but not all of the intensities of these features are correct. Other comparisons are shown for precipitation along the ITCZ, rediation balance, zonally averaged temperatures and zonal winds, and poleward transports of momentum and sensible heat.

  6. General order parameter based correlation analysis of protein backbone motions between experimental NMR relaxation measurements and molecular dynamics simulations

    SciTech Connect

    Liu, Qing; Shi, Chaowei; Yu, Lu; Zhang, Longhua; Xiong, Ying; Tian, Changlin

    2015-02-13

    Internal backbone dynamic motions are essential for different protein functions and occur on a wide range of time scales, from femtoseconds to seconds. Molecular dynamic (MD) simulations and nuclear magnetic resonance (NMR) spin relaxation measurements are valuable tools to gain access to fast (nanosecond) internal motions. However, there exist few reports on correlation analysis between MD and NMR relaxation data. Here, backbone relaxation measurements of {sup 15}N-labeled SH3 (Src homology 3) domain proteins in aqueous buffer were used to generate general order parameters (S{sup 2}) using a model-free approach. Simultaneously, 80 ns MD simulations of SH3 domain proteins in a defined hydrated box at neutral pH were conducted and the general order parameters (S{sup 2}) were derived from the MD trajectory. Correlation analysis using the Gromos force field indicated that S{sup 2} values from NMR relaxation measurements and MD simulations were significantly different. MD simulations were performed on models with different charge states for three histidine residues, and with different water models, which were SPC (simple point charge) water model and SPC/E (extended simple point charge) water model. S{sup 2} parameters from MD simulations with charges for all three histidines and with the SPC/E water model correlated well with S{sup 2} calculated from the experimental NMR relaxation measurements, in a site-specific manner. - Highlights: • Correlation analysis between NMR relaxation measurements and MD simulations. • General order parameter (S{sup 2}) as common reference between the two methods. • Different protein dynamics with different Histidine charge states in neutral pH. • Different protein dynamics with different water models.

  7. Nonequilibrium and generalized-ensemble molecular dynamics simulations for amyloid fibril

    SciTech Connect

    Okumura, Hisashi

    2015-12-31

    Amyloids are insoluble and misfolded fibrous protein aggregates and associated with more than 20 serious human diseases. We perform all-atom molecular dynamics simulations of amyloid fibril assembly and disassembly.

  8. A general kinetic-flow coupling model for FCC riser flow simulation.

    SciTech Connect

    Chang, S. L.

    1998-05-18

    A computational fluid dynamic (CFD) code has been developed for fluid catalytic cracking (FCC) riser flow simulation. Depending on the application of interest, a specific kinetic model is needed for the FCC flow simulation. This paper describes a method to determine a kinetic model based on limited pilot-scale test data. The kinetic model can then be used with the CFD code as a tool to investigate optimum operating condition ranges for a specific FCC unit.

  9. A general parallelization strategy for random path based geostatistical simulation methods

    NASA Astrophysics Data System (ADS)

    Mariethoz, Grégoire

    2010-07-01

    The size of simulation grids used for numerical models has increased by many orders of magnitude in the past years, and this trend is likely to continue. Efficient pixel-based geostatistical simulation algorithms have been developed, but for very large grids and complex spatial models, the computational burden remains heavy. As cluster computers become widely available, using parallel strategies is a natural step for increasing the usable grid size and the complexity of the models. These strategies must profit from of the possibilities offered by machines with a large number of processors. On such machines, the bottleneck is often the communication time between processors. We present a strategy distributing grid nodes among all available processors while minimizing communication and latency times. It consists in centralizing the simulation on a master processor that calls other slave processors as if they were functions simulating one node every time. The key is to decouple the sending and the receiving operations to avoid synchronization. Centralization allows having a conflict management system ensuring that nodes being simulated simultaneously do not interfere in terms of neighborhood. The strategy is computationally efficient and is versatile enough to be applicable to all random path based simulation methods.

  10. A Variable Resolution Stretched Grid General Circulation Model: Regional Climate Simulation

    NASA Technical Reports Server (NTRS)

    Fox-Rabinovitz, Michael S.; Takacs, Lawrence L.; Govindaraju, Ravi C.; Suarez, Max J.

    2000-01-01

    The development of and results obtained with a variable resolution stretched-grid GCM for the regional climate simulation mode, are presented. A global variable resolution stretched- grid used in the study has enhanced horizontal resolution over the U.S. as the area of interest The stretched-grid approach is an ideal tool for representing regional to global scale interaction& It is an alternative to the widely used nested grid approach introduced over a decade ago as a pioneering step in regional climate modeling. The major results of the study are presented for the successful stretched-grid GCM simulation of the anomalous climate event of the 1988 U.S. summer drought- The straightforward (with no updates) two month simulation is performed with 60 km regional resolution- The major drought fields, patterns and characteristics such as the time averaged 500 hPa heights precipitation and the low level jet over the drought area. appear to be close to the verifying analyses for the stretched-grid simulation- In other words, the stretched-grid GCM provides an efficient down-scaling over the area of interest with enhanced horizontal resolution. It is also shown that the GCM skill is sustained throughout the simulation extended to one year. The developed and tested in a simulation mode stretched-grid GCM is a viable tool for regional and subregional climate studies and applications.

  11. Simulated scaling method for localized enhanced sampling and simultaneous "alchemical" free energy simulations: a general method for molecular mechanical, quantum mechanical, and quantum mechanical/molecular mechanical simulations.

    PubMed

    Li, Hongzhi; Fajer, Mikolai; Yang, Wei

    2007-01-14

    A potential scaling version of simulated tempering is presented to efficiently sample configuration space in a localized region. The present "simulated scaling" method is developed with a Wang-Landau type of updating scheme in order to quickly flatten the distributions in the scaling parameter lambdam space. This proposal is meaningful for a broad range of biophysical problems, in which localized sampling is required. Besides its superior capability and robustness in localized conformational sampling, this simulated scaling method can also naturally lead to efficient "alchemical" free energy predictions when dual-topology alchemical hybrid potential is applied; thereby simultaneously, both of the chemically and conformationally distinct portions of two end point chemical states can be efficiently sampled. As demonstrated in this work, the present method is also feasible for the quantum mechanical and quantum mechanical/molecular mechanical simulations.

  12. General practice registrar responses to the use of different risk communication tools in simulated consultations: a focus group study

    PubMed Central

    Edwards, Adrian; Elwyn, Glyn; Gwyn, Richard

    1999-01-01

    Objectives To pilot the use of a range of complementary risk communication tools in simulated general practice consultations; to gauge the responses of general practitioners in training to these new consultation aids. Design Qualitative study based on focus group discussions. Setting General practice vocational training schemes in South Wales. Participants 39 general practice registrars and eight course organisers attended four sessions; three simulated patients attended each time. Method Registrars consulting with simulated patients used verbal or “qualitative” descriptions of risks, then numerical data, and finally graphical presentations of the same data. Responses of doctors and patients were explored by semistructured discussions that had been audiotaped for transcription and analysis. Results The process of using risk communication tools in simulated consultations was acceptable to general practitioner registrars. Providing doctors with information about risks and benefits of treatment options was generally well received. Both doctors and patients found it helped communication. There were concerns about the lack of available, unbiased, and applicable evidence and a shortage of time in the consultation to discuss treatment options adequately. Graphical presentation of information was often favoured—an approach that also has the potential to save consultation time. Conclusions A range of risk communication “tools” with which to discuss treatment options is likely to be more applicable than a single new strategy. These tools should include both absolute and relative risk information formats, presented in an unbiased way. Using risk communication tools in simulated consultations provides a model for training in risk communication for professional groups. Key messagesInvolving patients in decisions about their treatment or care improves health outcomesSuccessful involvement of patients requires effective communication of risksHaving a range of risk

  13. A virtual reality endoscopic simulator augments general surgery resident cancer education as measured by performance improvement.

    PubMed

    White, Ian; Buchberg, Brian; Tsikitis, V Liana; Herzig, Daniel O; Vetto, John T; Lu, Kim C

    2014-06-01

    Colorectal cancer is the second most common cause of death in the USA. The need for screening colonoscopies, and thus adequately trained endoscopists, particularly in rural areas, is on the rise. Recent increases in required endoscopic cases for surgical resident graduation by the Surgery Residency Review Committee (RRC) further emphasize the need for more effective endoscopic training during residency to determine if a virtual reality colonoscopy simulator enhances surgical resident endoscopic education by detecting improvement in colonoscopy skills before and after 6 weeks of formal clinical endoscopic training. We conducted a retrospective review of prospectively collected surgery resident data on an endoscopy simulator. Residents performed four different clinical scenarios on the endoscopic simulator before and after a 6-week endoscopic training course. Data were collected over a 5-year period from 94 different residents performing a total of 795 colonoscopic simulation scenarios. Main outcome measures included time to cecal intubation, "red out" time, and severity of simulated patient discomfort (mild, moderate, severe, extreme) during colonoscopy scenarios. Average time to intubation of the cecum was 6.8 min for those residents who had not undergone endoscopic training versus 4.4 min for those who had undergone endoscopic training (p < 0.001). Residents who could be compared against themselves (pre vs. post-training), cecal intubation times decreased from 7.1 to 4.3 min (p < 0.001). Post-endoscopy rotation residents caused less severe discomfort during simulated colonoscopy than pre-endoscopy rotation residents (4 vs. 10%; p = 0.004). Virtual reality endoscopic simulation is an effective tool for both augmenting surgical resident endoscopy cancer education and measuring improvement in resident performance after formal clinical endoscopic training.

  14. A general spectral method for the numerical simulation of one-dimensional interacting fermions

    NASA Astrophysics Data System (ADS)

    Clason, Christian; von Winckel, Gregory

    2012-08-01

    This software implements a general framework for the direct numerical simulation of systems of interacting fermions in one spatial dimension. The approach is based on a specially adapted nodal spectral Galerkin method, where the basis functions are constructed to obey the antisymmetry relations of fermionic wave functions. An efficient Matlab program for the assembly of the stiffness and potential matrices is presented, which exploits the combinatorial structure of the sparsity pattern arising from this discretization to achieve optimal run-time complexity. This program allows the accurate discretization of systems with multiple fermions subject to arbitrary potentials, e.g., for verifying the accuracy of multi-particle approximations such as Hartree-Fock in the few-particle limit. It can be used for eigenvalue computations or numerical solutions of the time-dependent Schrödinger equation. The new version includes a Python implementation of the presented approach. New version program summaryProgram title: assembleFermiMatrix Catalogue identifier: AEKO_v1_1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKO_v1_1.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 332 No. of bytes in distributed program, including test data, etc.: 5418 Distribution format: tar.gz Programming language: MATLAB/GNU Octave, Python Computer: Any architecture supported by MATLAB, GNU Octave or Python Operating system: Any supported by MATLAB, GNU Octave or Python RAM: Depends on the data Classification: 4.3, 2.2. External routines: Python 2.7+, NumPy 1.3+, SciPy 0.10+ Catalogue identifier of previous version: AEKO_v1_0 Journal reference of previous version: Comput. Phys. Commun. 183 (2012) 405 Does the new version supersede the previous version?: Yes Nature of problem: The direct numerical

  15. Numerical Simulations of Blood Flow in a Stenosed Vessel under Different Flow Rates using a Generalized Oldroyd-B Model

    NASA Astrophysics Data System (ADS)

    Bodnár, T.; Sequeira, A.; Pirkl, L.

    2009-09-01

    The present paper discusses the influence and importance of the application of generalized Newtonian and generalized viscoelastic models to blood flow simulations. A simple shear-thinning viscosity model together with a Oldroyd-B model for the viscoelastic part of the stress was applied to a simplified test case of stenosed vessel. The direct comparison between results of Newtonian and non-Newtonian flows is presented for various flow rates. The aim of the study is to test the applicability of the presented numerical method to this type of flows.

  16. NeuroFlow: A General Purpose Spiking Neural Network Simulation Platform using Customizable Processors

    PubMed Central

    Cheung, Kit; Schultz, Simon R.; Luk, Wayne

    2016-01-01

    NeuroFlow is a scalable spiking neural network simulation platform for off-the-shelf high performance computing systems using customizable hardware processors such as Field-Programmable Gate Arrays (FPGAs). Unlike multi-core processors and application-specific integrated circuits, the processor architecture of NeuroFlow can be redesigned and reconfigured to suit a particular simulation to deliver optimized performance, such as the degree of parallelism to employ. The compilation process supports using PyNN, a simulator-independent neural network description language, to configure the processor. NeuroFlow supports a number of commonly used current or conductance based neuronal models such as integrate-and-fire and Izhikevich models, and the spike-timing-dependent plasticity (STDP) rule for learning. A 6-FPGA system can simulate a network of up to ~600,000 neurons and can achieve a real-time performance of 400,000 neurons. Using one FPGA, NeuroFlow delivers a speedup of up to 33.6 times the speed of an 8-core processor, or 2.83 times the speed of GPU-based platforms. With high flexibility and throughput, NeuroFlow provides a viable environment for large-scale neural network simulation. PMID:26834542

  17. Ensemble climate simulations using a fully coupled ocean-troposphere-stratosphere general circulation model.

    PubMed

    Huebener, H; Cubasch, U; Langematz, U; Spangehl, T; Niehörster, F; Fast, I; Kunze, M

    2007-08-15

    Long-term transient simulations are carried out in an initial condition ensemble mode using a global coupled climate model which includes comprehensive ocean and stratosphere components. This model, which is run for the years 1860-2100, allows the investigation of the troposphere-stratosphere interactions and the importance of representing the middle atmosphere in climate-change simulations. The model simulates the present-day climate (1961-2000) realistically in the troposphere, stratosphere and ocean. The enhanced stratospheric resolution leads to the simulation of sudden stratospheric warmings; however, their frequency is underestimated by a factor of 2 with respect to observations.In projections of the future climate using the Intergovernmental Panel on Climate Change special report on emissions scenarios A2, an increased tropospheric wave forcing counteracts the radiative cooling in the middle atmosphere caused by the enhanced greenhouse gas concentration. This leads to a more dynamically active, warmer stratosphere compared with present-day simulations, and to the doubling of the number of stratospheric warmings. The associated changes in the mean zonal wind patterns lead to a southward displacement of the Northern Hemisphere storm track in the climate-change signal.

  18. NeuroFlow: A General Purpose Spiking Neural Network Simulation Platform using Customizable Processors.

    PubMed

    Cheung, Kit; Schultz, Simon R; Luk, Wayne

    2015-01-01

    NeuroFlow is a scalable spiking neural network simulation platform for off-the-shelf high performance computing systems using customizable hardware processors such as Field-Programmable Gate Arrays (FPGAs). Unlike multi-core processors and application-specific integrated circuits, the processor architecture of NeuroFlow can be redesigned and reconfigured to suit a particular simulation to deliver optimized performance, such as the degree of parallelism to employ. The compilation process supports using PyNN, a simulator-independent neural network description language, to configure the processor. NeuroFlow supports a number of commonly used current or conductance based neuronal models such as integrate-and-fire and Izhikevich models, and the spike-timing-dependent plasticity (STDP) rule for learning. A 6-FPGA system can simulate a network of up to ~600,000 neurons and can achieve a real-time performance of 400,000 neurons. Using one FPGA, NeuroFlow delivers a speedup of up to 33.6 times the speed of an 8-core processor, or 2.83 times the speed of GPU-based platforms. With high flexibility and throughput, NeuroFlow provides a viable environment for large-scale neural network simulation.

  19. The simulated features of heliospheric cosmic-ray modulation with a time-dependent drift model. III - General energy dependence

    NASA Technical Reports Server (NTRS)

    Potgieter, M. S.; Le Roux, J. A.

    1992-01-01

    The time-dependent cosmic-ray transport equation is solved numerically in an axially symmetric heliosphere. Gradient and curvature drifts are incorporated, together with an emulated wavy neutral sheet. This model is used to simulate heliospheric cosmic-ray modulation for the period 1985-1989 during which drifts are considered to be important. The general energy dependence of the modulation of Galactic protons is studied as predicted by the model for the energy range 1 MeV to 10 GeV. The corresponding instantaneous radial and latitudinal gradients are calculated, and it is found that, whereas the latitudinal gradients follow the trends in the waviness of the neutral sheet to a large extent for all energies, the radial gradients below about 200 MeV deviate from this general pattern. In particular, these gradients increase when the waviness decreases for the simulated period 1985-1987.3, after which they again follow the neutral sheet by increasing rapidly.

  20. Repeated simulation-based training for performing general anesthesia for emergency cesarean delivery: long-term retention and recurring mistakes.

    PubMed

    Ortner, C M; Richebé, P; Bollag, L A; Ross, B K; Landau, R

    2014-11-01

    The percentage of women undergoing cesarean delivery under general anesthesia has significantly decreased, which limits training opportunities for its safe administration. The purpose of this study was to evaluate how effective simulation-based training was in the learning and long-term retention of skills to perform general anesthesia for an emergent cesarean delivery. During an eight-week obstetric anesthesia rotation, 24 residents attended lectures and simulation-based training to perform general anesthesia for emergent cesarean delivery. Performance assessments using a validated weighted scaling system were made during the first (pre-test) and fifth weeks (post-test) of training, and eight months later (post-retention test). Resident's competency level (weighted score) and errors were assessed at each testing session. Six obstetric anesthesia attending physicians, unfamiliar with the simulation scenario, generated a mean attendings' performance score. The results were compared. At one week of training, residents' performance was significantly below mean attendings' performance score (pre-test: 135±22 vs. 159±11, P=0.013). At five weeks, residents' performance was similar to mean attendings' performance score (post-test: 159±21) and remained at that level at eight months (post-retention test: 164±16). Of the important obstetric-specific tasks, left uterine displacement was missed by 46% of residents at eight months. Following lectures and simulation-enhanced training, anesthesia residents reached and retained for up to eight months a competency level in a simulator comparable to that of obstetric anesthesia attending physicians. Errors in performance and missed tasks may be used to improve residency training and continuing medical education. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Simulations of Madden-Julian Oscillation in High Resolution Atmospheric General Circulation Model

    NASA Astrophysics Data System (ADS)

    Deng, Liping; Stenchikov, Georgiy; McCabe, Matthew; Bangalath, HamzaKunhu; Raj, Jerry; Osipov, Sergey

    2014-05-01

    The simulation of tropical signals, especially the Madden-Julian Oscillation (MJO), is one of the major deficiencies in current numerical models. The unrealistic features in the MJO simulations include the weak amplitude, more power at higher frequencies, displacement of the temporal and spatial distributions, eastward propagation speed being too fast, and a lack of coherent structure for the eastward propagation from the Indian Ocean to the Pacific (e.g., Slingo et al. 1996). While some improvement in simulating MJO variance and coherent eastward propagation has been attributed to model physics, model mean background state and air-sea interaction, studies have shown that the model resolution, especially for higher horizontal resolution, may play an important role in producing a more realistic simulation of MJO (e.g., Sperber et al. 2005). In this study, we employ unique high-resolution (25-km) simulations conducted using the Geophysical Fluid Dynamics Laboratory global High Resolution Atmospheric Model (HIRAM) to evaluate the MJO simulation against the European Center for Medium-range Weather Forecasts (ECMWF) Interim re-analysis (ERAI) dataset. We specifically focus on the ability of the model to represent the MJO related amplitude, spatial distribution, eastward propagation, and horizontal and vertical structures. Additionally, as the HIRAM output covers not only an historic period (1979-2012) but also future period (2012-2050), the impact of future climate change related to the MJO is illustrated. The possible changes in intensity and frequency of extreme weather and climate events (e.g., strong wind and heavy rainfall) in the western Pacific, the Indian Ocean and the Middle East North Africa (MENA) region are highlighted.

  2. A general and predictive model of anisotropic grain boundary energy and morphology for polycrystal-level simulations

    NASA Astrophysics Data System (ADS)

    Runnels, Brandon; Beyerlein, Irene; Conti, Sergio; Ortiz, Michael

    In this work, a new model for anisotropic GB energy and morphology is formulated that is fast, general, dependent on only three material parameters, and is verified by comparison with more than 40 MD and experimental datasets for (a)symmetric, tilt/twist, FCC/BCC materials, as well as experimental measurements. A relaxation algorithm is presented that is able to efficiently compute the optimal facet pattern and corresponding relaxed energy. Finally, the GB model is implemented as an interface model in a polycrystal simulation to observe the effects of GB in conjunction with elastic and plastic deformation. The simulations are compared with those using an isotropic GB model, and the effect of the GB isotropy on the bulk properties and microstructure is determined. The results have applications towards, e.g., improved polycrystal simulations, understanding void nucleation, and GB engineering.

  3. An investigation on the body force modeling in a lattice Boltzmann BGK simulation of generalized Newtonian fluids

    NASA Astrophysics Data System (ADS)

    Farnoush, Somayeh; Manzari, Mehrdad T.

    2014-12-01

    Body force modeling is studied in the Generalized Newtonian (GN) fluid flow simulation using a single relaxation time lattice Boltzmann (LB) method. First, in a shear thickening Poiseuille flow, the necessity for studying body force modeling in the LB method is explained. Then, a parametric unified framework is constructed for the first time which is composed of a parametric LB model and its associated macroscopic dual equations in both steady state and transient simulations. This unified framework is used to compare the macroscopic behavior of different forcing models. Besides, using this unified framework, a new forcing model for steady state simulations is devised. Finally, by solving a number of test cases it is shown that numerical results confirm the theoretical arguments presented in this paper.

  4. Turning Simulation into Estimation: Generalized Exchange Algorithms for Exponential Family Models

    PubMed Central

    Maris, Gunter; Bechger, Timo; Glas, Cees

    2017-01-01

    The Single Variable Exchange algorithm is based on a simple idea; any model that can be simulated can be estimated by producing draws from the posterior distribution. We build on this simple idea by framing the Exchange algorithm as a mixture of Metropolis transition kernels and propose strategies that automatically select the more efficient transition kernels. In this manner we achieve significant improvements in convergence rate and autocorrelation of the Markov chain without relying on more than being able to simulate from the model. Our focus will be on statistical models in the Exponential Family and use two simple models from educational measurement to illustrate the contribution. PMID:28076429

  5. A study of nucleation and growth of thin films by means of computer simulation: General features

    NASA Technical Reports Server (NTRS)

    Salik, J.

    1984-01-01

    Some of the processes involved in the nucleation and growth of thin films were simulated by means of a digital computer. The simulation results were used to study the nucleation and growth kinetics resulting from the various processes. Kinetic results obtained for impingement, surface migration, impingement combined with surface migration, and with reevaporation are presented. A substantial fraction of the clusters may form directly upon impingement. Surface migration results in a decrease in cluster density, and reevaporation of atoms from the surface causes a further reduction in cluster density.

  6. The global distribution of natural tritium in precipitation simulated with an Atmospheric General Circulation Model and comparison with observations

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Jean-Baptiste, P.; Risi, C.; Fourré, É.; Stenni, B.; Landais, A.

    2015-10-01

    The description of the hydrological cycle in Atmospheric General Circulation Models (GCMs) can be validated using water isotopes as tracers. Many GCMs now simulate the movement of the stable isotopes of water, but here we present the first GCM simulations modelling the content of natural tritium in water. These simulations were obtained using a version of the LMDZ General Circulation Model enhanced by water isotopes diagnostics, LMDZ-iso. To avoid tritium generated by nuclear bomb testing, the simulations have been evaluated against a compilation of published tritium datasets dating from before 1950, or measured recently. LMDZ-iso correctly captures the observed tritium enrichment in precipitation as oceanic air moves inland (the so-called continental effect) and the observed north-south variations due to the latitudinal dependency of the cosmogenic tritium production rate. The seasonal variability, linked to the stratospheric intrusions of air masses with higher tritium content into the troposphere, is correctly reproduced for Antarctica with a maximum in winter. LMDZ-iso reproduces the spring maximum of tritium over Europe, but underestimates it and produces a peak in winter that is not apparent in the data. This implementation of tritium in a GCM promises to provide a better constraint on: (1) the intrusions and transport of air masses from the stratosphere, and (2) the dynamics of the modelled water cycle. The method complements the existing approach of using stable water isotopes.

  7. Maternally Derived Immunity Extends Swine Influenza A Virus Persistence within Farrow-to-Finish Pig Farms: Insights from a Stochastic Event-Driven Metapopulation Model

    PubMed Central

    Cador, Charlie; Rose, Nicolas; Willem, Lander; Andraud, Mathieu

    2016-01-01

    Swine Influenza A Viruses (swIAVs) have been shown to persist in farrow-to-finish pig herds with repeated outbreaks in successive batches, increasing the risk for respiratory disorders in affected animals and being a threat for public health. Although the general routes of swIAV transmission (i.e. direct contact and exposure to aerosols) were clearly identified, the transmission process between batches is still not fully understood. Maternally derived antibodies (MDAs) were stressed as a possible factor favoring within-herd swIAV persistence. However, the relationship between MDAs and the global spread among the different subpopulations in the herds is still lacking. The aim of this study was therefore to understand the mechanisms induced by MDAs in relation with swIAV spread and persistence in farrow-to-finish pig herds. A metapopulation model has been developed representing the population dynamics considering two subpopulations—breeding sows and growing pigs—managed according to batch-rearing system. This model was coupled with a swIAV-specific epidemiological model, accounting for partial passive immunity protection in neonatal piglets and an immunity boost in re-infected animals. Airborne transmission was included by a between-room transmission rate related to the current prevalence of shedding pigs. Maternally derived partial immunity in piglets was found to extend the duration of the epidemics within their batch, allowing for efficient between-batch transmission and resulting in longer swIAV persistence at the herd level. These results should be taken into account in the design of control programmes for the spread and persistence of swIAV in swine herds. PMID:27662592

  8. Accurate and general treatment of electrostatic interaction in Hamiltonian adaptive resolution simulations

    NASA Astrophysics Data System (ADS)

    Heidari, M.; Cortes-Huerto, R.; Donadio, D.; Potestio, R.

    2016-10-01

    In adaptive resolution simulations the same system is concurrently modeled with different resolution in different subdomains of the simulation box, thereby enabling an accurate description in a small but relevant region, while the rest is treated with a computationally parsimonious model. In this framework, electrostatic interaction, whose accurate treatment is a crucial aspect in the realistic modeling of soft matter and biological systems, represents a particularly acute problem due to the intrinsic long-range nature of Coulomb potential. In the present work we propose and validate the usage of a short-range modification of Coulomb potential, the Damped shifted force (DSF) model, in the context of the Hamiltonian adaptive resolution simulation (H-AdResS) scheme. This approach, which is here validated on bulk water, ensures a reliable reproduction of the structural and dynamical properties of the liquid, and enables a seamless embedding in the H-AdResS framework. The resulting dual-resolution setup is implemented in the LAMMPS simulation package, and its customized version employed in the present work is made publicly available.

  9. PERSYM: A Generalized Entity - Simulation Model of a Military Personnel System.

    ERIC Educational Resources Information Center

    Groover, Robert O.

    The document covers an operational entity-simulation system designed to permit observation and selective control of a military personnel system under a variety of policy alternatives. PERSYM is modularized to facilitate conversion to different military forces and the programing and inclusion of alternative policy logic modules. The system…

  10. Generalized methodology for modeling and simulating optical interconnection networks using diffraction analysis

    NASA Astrophysics Data System (ADS)

    Louri, Ahmed; Major, Michael C.

    1995-07-01

    Research in the field of free-space optical interconnection networks has reached a point where simula-tors and other design tools are desirable for reducing development costs and for improving design time. Previously proposed methodologies have only been applicable to simple systems. Our goal was to develop a simulation methodology capable of evaluating the performance characteristics for a variety of different free-space networks under a range of different configurations and operating states. The proposed methodology operates by first establishing the optical signal powers at various locations in the network. These powers are developed through the simulation by diffraction analysis of the light propagation through the network. After this evaluation, characteristics such as bit-error rate, signal-to-noise ratio, and system bandwidth are calculated. Further, the simultaneous evaluation of this process for a set of component misalignments provides a measure of the alignment tolerance of a design. We discuss this simulation process in detail as well as provide models for different optical interconnection network components.

  11. A Simpli ed, General Approach to Simulating from Multivariate Copula Functions

    Treesearch

    Barry Goodwin

    2012-01-01

    Copulas have become an important analytic tool for characterizing multivariate distributions and dependence. One is often interested in simulating data from copula estimates. The process can be analytically and computationally complex and usually involves steps that are unique to a given parametric copula. We describe an alternative approach that uses \\probability{...

  12. A note on a simplified and general approach to simulating from multivariate copula functions

    Treesearch

    Barry K. Goodwin

    2013-01-01

    Copulas have become an important analytic tool for characterizing multivariate distributions and dependence. One is often interested in simulating data from copula estimates. The process can be analytically and computationally complex and usually involves steps that are unique to a given parametric copula. We describe an alternative approach that uses ‘Probability-...

  13. Speed of spinal vs general anaesthesia for category-1 caesarean section: a simulation and clinical observation-based study.

    PubMed

    Kathirgamanathan, A; Douglas, M J; Tyler, J; Saran, S; Gunka, V; Preston, R; Kliffer, P

    2013-07-01

    Controversy exists as to whether effective spinal anaesthesia can be achieved as quickly as general anaesthesia for a category-1 caesarean section. Sixteen consultants and three fellows in obstetric anaesthesia were timed performing spinal and general anaesthesia for category-1 caesarean section on a simulator. The simulation time commenced upon entry of the anaesthetist into the operating theatre and finished for the spinal anaesthetic at the end of intrathecal injection and for the general anaesthetic when the anaesthetist was happy for surgery to start. In the second clinical part of the study, the time from intrathecal administration to 'adequate surgical anaesthesia' (defined as adequate for start of a category-1 caesarean section) was estimated in 100 elective (category-4) caesarean sections. The median (IQR [range]) times (min:s) for spinal procedure, onset of spinal block and general anaesthesia were 2:56 (2:32-3:32 [1:22-3:50]), 5:56 (4:23-7:39 [2:9-13:32]) and 1:56 (1:39-2:9 [1:13-3:12]), respectively. The limiting factor in urgent spinal anaesthesia is the unpredictable time needed for adequate surgical block to develop.

  14. Field-based DGTD/PIC technique for general and stable simulation of interaction between light and electron bunches

    NASA Astrophysics Data System (ADS)

    Fallahi, Arya; Kärtner, Franz

    2014-12-01

    We introduce a hybrid technique based on the discontinuous Galerkin time domain (DGTD) and the particle in cell (PIC) simulation methods for the analysis of interaction between light and charged particles. The DGTD algorithm is a three-dimensional, dual-field and fully explicit method for efficiently solving Maxwell equations in the time domain on unstructured grids. On the other hand, the PIC algorithm is a versatile technique for the simulation of charged particles in an electromagnetic field. This paper introduces a novel strategy for combining both methods to solve for the electron motion and field distribution when an optical beam interacts with an electron bunch in a very general geometry. The developed software offers a complete and stable numerical solution of the problem for arbitrary charge and field distributions in the time domain on unstructured grids. For this purpose, an advanced search algorithm is developed for fast calculation of field data at charge points and for later importing to the PIC simulations. In addition, we propose a field-based coupling between the two methods resulting in a stable and precise time marching scheme for both fields and charged particle motion. To benchmark the solver, some examples are numerically solved and compared with analytical solutions. Eventually, the developed software is utilized to simulate the field emission from a flat metal plate and a silicon nano-tip. In the future, we will use this technique for the simulation and design of ultrafast compact x-ray sources.

  15. Generalized Wind Turbine Actuator Disk Parameterization in the Weather Research and Forecasting (WRF) Model for Real-World Simulations

    NASA Astrophysics Data System (ADS)

    Marjanovic, N.; Mirocha, J. D.; Chow, F. K.

    2013-12-01

    In this work, we examine the performance of a generalized actuator disk (GAD) model embedded within the Weather Research and Forecasting (WRF) atmospheric model to study wake effects on successive rows of turbines at a North American wind farm. These wake effects are of interest as they can drastically reduce down-wind energy extraction and increase turbulence intensity. The GAD, which is designed for turbulence-resolving simulations, is used within downscaled large-eddy simulations (LES) forced with mesoscale simulations and WRF's grid nesting capability. The GAD represents the effects of thrust and torque created by a wind turbine on the atmosphere within a disk representing the rotor swept area. The lift and drag forces acting on the turbine blades are parameterized using blade-element theory and the aerodynamic properties of the blades. Our implementation permits simulation of turbine wake effects and turbine/airflow interactions within a realistic atmospheric boundary layer flow field, including resolved turbulence, time-evolving mesoscale forcing, and real topography. The GAD includes real-time yaw and pitch control to respond realistically to changing flow conditions. Simulation results are compared to SODAR data from operating wind turbines and an already existing WRF mesoscale turbine drag parameterization to validate the GAD parameterization.

  16. Atmospheric distribution of Kr-85 simulated with a general circulation model

    NASA Technical Reports Server (NTRS)

    Jacob, Daniel J.; Wofsy, Steven C.; Mcelroy, Michael B.; Prather, Michael J.

    1987-01-01

    A three-dimensional chemical tracer model for the troposphere is used to simulate the global distribution of Kr-85, a long-lived radioisotope released at northern midlatitudes by nuclear industry. Simulated distributions for the period 1980-1983 are in excellent agreement with data from six latitudinal profiles measured over the Atlantic. High concentrations of Kr-85 are predicted over the Arctic in winter, advected from European sources, and somewhat smaller enhancements arising from the same sources are predicted over the tropical Atlantic in summer. Latitudinal gradients are steepest in the northern tropics, with distinctly different seasonal variations over the Pacific, as compared to the Atlantic. The global inventory of Kr-85 is reconstructed for the period 1980-1983 by combining the concentrations measured over the Atlantic with the global distributions predicted by the model. The magnitude of the Soviet source is derived. The interhemispheric exchange time is calculated as 1.1 years, with little seasonal dependence.

  17. Earth radiation budget and cloudiness simulations with a general circulation model

    NASA Technical Reports Server (NTRS)

    HARSHVARDHAN; Randall, David A.; Corsetti, Thomas G.; Dazlich, Donald A.

    1989-01-01

    A GCM with new parameterizations of solar and terrestrial radiation, parameterized cloud optical properties, and a simple representation of the cloud liquid water feedback is used with several observational data sets to analyze the effects of cloudiness on the earth's radiation budget. The January and July results from the model are in reasonable agreement with data from Nimbus-7. It is found that the simulated cloudiness overpredicts subtropical and midlatitude cloudiness. The simulated atmospheric cloud radiative forcing is examined. The clear-sky radiation fields obtained by two methods of Cess and Potter (1987) are compared. Also, a numerical experiment was performed to determine the effects of the water vapor continuum on the model results.

  18. Can teenage novel users perform as well as General Surgery residents upon initial exposure to a robotic surgical system simulator?

    PubMed

    Mehta, A; Patel, S; Robison, W; Senkowski, T; Allen, J; Shaw, E; Senkowski, C

    2017-06-05

    New techniques in minimally invasive and robotic surgical platforms require staged curricula to insure proficiency. Scant literature exists as to how much simulation should play a role in training those who have skills in advanced surgical technology. The abilities of novel users may help discriminate if surgically experienced users should start at a higher simulation level or if the tasks are too rudimentary. The study's purpose is to explore the ability of General Surgery residents to gain proficiency on the dVSS as compared to novel users. The hypothesis is that Surgery residents will have increased proficiency in skills acquisition as compared to naive users. Six General Surgery residents at a single institution were compared with six teenagers using metrics measured by the dVSS. Participants were given two 1-h sessions to achieve an MScoreTM in the 90th percentile on each of the five simulations. MScoreTM software compiles a variety of metrics including total time, number of attempts, and high score. Statistical analysis was run using Student's t test. Significance was set at p value <0.05. Total time, attempts, and high score were compared between the two groups. The General Surgery residents took significantly less Total Time to complete Pegboard 1 (PB1) (p = 0.043). No significant difference was evident between the two groups in the other four simulations across the same MScoreTM metrics. A focused look at the energy dissection task revealed that overall score might not be discriminant enough. Our findings indicate that prior medical knowledge or surgical experience does not significantly impact one's ability to acquire new skills on the dVSS. It is recommended that residency-training programs begin to include exposure to robotic technology.

  19. Spring: a general framework for collaborative, real-time surgical simulation.

    PubMed

    Montgomery, Kevin; Bruyns, Cynthia; Brown, Joel; Sorkin, Stephen; Mazzella, Frederic; Thonier, Guillaume; Tellier, Arnaud; Lerman, Benjamin; Menon, Anil

    2002-01-01

    We describe the implementation details of a real-time surgical simulation system with soft-tissue modeling and multi-user, multi-instrument, networked haptics. The simulator is cross-platform and runs on various Unix and Windows platforms. It is written in C++ with OpenGL for graphics; GLUT, GLUI, and MUI for user interface; and supports parallel processing. It allows for the relatively easy introduction of patient-specific anatomy and supports many common file formats. It performs soft-tissue modeling, some limited rigid-body dynamics, and suture modeling. The simulator interfaces to many different interaction devices and provides for multi-user, multi-instrument collaboration over the Internet. Many virtual tools have been created and their interactions with tissue have been implemented. In addition, a number of extra features, such as voice input/output, real-time texture-mapped video input, stereo and head-mounted display support, and replicated display facilities are presented.

  20. General Relativistic Magnetohydrodynamic Simulations of Jet Formation with a Thin Keplerian Disk

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Nishikawa, Ken-Ichi; Koide, Shinji; Hardee, Philip; Gerald, J. Fishman

    2006-01-01

    We have performed several simulations of black hole systems (non-rotating, black hole spin parameter a = 0.0 and rapidly rotating, a = 0.95) with a geometrically thin Keplerian disk using the newly developed RAISHIN code. The simulation results show the formation of jets driven by the Lorentz force and the gas pressure gradient. The jets have mildly relativistic speed (greater than or equal to 0.4 c). The matter is continuously supplied from the accretion disk and the jet propagates outward until each applicable terminal simulation time (non-rotating: t/tau S = 275 and rotating: t/tau S = 200, tau s equivalent to r(sub s/c). It appears that a rotating black hole creates an additional, faster, and more collimated inner outflow (greater than or equal to 0.5 c) formed and accelerated by the twisted magnetic field resulting from frame-dragging in the black hole ergosphere. This new result indicates that jet kinematic structure depends on black hole rotation.

  1. Developing extensible lattice-Boltzmann simulators for general-purpose graphics-processing units

    SciTech Connect

    Walsh, S C; Saar, M O

    2011-12-21

    Lattice-Boltzmann methods are versatile numerical modeling techniques capable of reproducing a wide variety of fluid-mechanical behavior. These methods are well suited to parallel implementation, particularly on the single-instruction multiple data (SIMD) parallel processing environments found in computer graphics processing units (GPUs). Although more recent programming tools dramatically improve the ease with which GPU programs can be written, the programming environment still lacks the flexibility available to more traditional CPU programs. In particular, it may be difficult to develop modular and extensible programs that require variable on-device functionality with current GPU architectures. This paper describes a process of automatic code generation that overcomes these difficulties for lattice-Boltzmann simulations. It details the development of GPU-based modules for an extensible lattice-Boltzmann simulation package - LBHydra. The performance of the automatically generated code is compared to equivalent purpose written codes for both single-phase, multiple-phase, and multiple-component flows. The flexibility of the new method is demonstrated by simulating a rising, dissolving droplet in a porous medium with user generated lattice-Boltzmann models and subroutines.

  2. Effectiveness of using high-fidelity simulation to teach the management of general anesthesia for Cesarean delivery.

    PubMed

    Balki, Mrinalini; Chakravarty, Subrata; Salman, Aliya; Wax, Randy S

    2014-10-01

    The objective of this study was to assess the influence of a teaching plan consisting of didactic teaching and repeated simulations on the performance of anesthesia residents in the management of general anesthesia (GA) for emergency Cesarean delivery (CD). Twenty-one postgraduate year 2 (PGY2) and 3 (PGY3) anesthesia residents from the University of Toronto were recruited in this prospective cohort study. All participants received didactic teaching in the management of GA for emergency CD, which was followed one week later by assessment of performance in the same scenario using a high-fidelity simulator. Another simulation assessment was repeated two months later in the same scenario. All simulation video recordings were assessed by two blinded experts using a validated checklist and an Anaesthetists' Non-Technical Skills (ANTS) scale in order to rate their technical and non-technical skills, respectively. The participants' performance (based on the above scales) in the two simulation sessions were then compared. Nineteen residents completed both simulation sessions. There was an improvement in the mean (SD) weighted checklist score from 64.5% (7.1%) in session 1 to 76.7% (6.7%) in session 2 (P < 0.001). The mean (SD) ANTS scores also increased from 2.8 (0.5) in session 1 to 3.3 (0.4) in session 2 (P = 0.001). No difference in the checklist or ANTS scores was seen between PGY2 and PGY3 residents in any of the simulation sessions. Several common performance errors were identified, but these improved in the second session. The correlation between checklist and ANTS scores was moderately high (correlation coefficient [r] = 0.7; P < 0.001). The inter-rater reliability among the experts was also high (intraclass correlation coefficient [ICC] for the checklist = 0.72; 95% confidence interval [CI] 0.62 to 0.81; ICC for the ANTS = 0.74; 95% CI 0.49 to 0.89). Didactic teaching followed by simulation sessions enhances not only the technical skills but also the

  3. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    NASA Astrophysics Data System (ADS)

    Jöckel, P.; Tost, H.; Pozzer, A.; Brühl, C.; Buchholz, J.; Ganzeveld, L.; Hoor, P.; Kerkweg, A.; Lawrence, M. G.; Sander, R.; Steil, B.; Stiller, G.; Tanarhte, M.; Taraborrelli, D.; van Aardenne, J.; Lelieveld, J.

    2006-11-01

    The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model setup up to 0.01 hPa was used at spectral T42 resolution to simulate the lower and middle atmosphere. With the high vertical resolution the model simulates the Quasi-Biennial Oscillation. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. In the simulations presented here a Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998-2005. This allows an efficient and direct evaluation with satellite and in-situ data. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated well, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of inter-annual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the

  4. Generalized Simulation Model for a Switched-Mode Power Supply Design Course Using MATLAB/SIMULINK

    ERIC Educational Resources Information Center

    Liao, Wei-Hsin; Wang, Shun-Chung; Liu, Yi-Hua

    2012-01-01

    Switched-mode power supplies (SMPS) are becoming an essential part of many electronic systems as the industry drives toward miniaturization and energy efficiency. However, practical SMPS design courses are seldom offered. In this paper, a generalized MATLAB/SIMULINK modeling technique is first presented. A proposed practical SMPS design course at…

  5. Simulation of the Low-Level-Jet by general circulation models

    SciTech Connect

    Ghan, S.J.

    1996-04-01

    To what degree is the low-level jet climatology and it`s impact on clouds and precipitation being captured by current general circulation models? It is hypothesised that a need for a pramaterization exists. This paper describes this parameterization need.

  6. Generalized Simulation Model for a Switched-Mode Power Supply Design Course Using MATLAB/SIMULINK

    ERIC Educational Resources Information Center

    Liao, Wei-Hsin; Wang, Shun-Chung; Liu, Yi-Hua

    2012-01-01

    Switched-mode power supplies (SMPS) are becoming an essential part of many electronic systems as the industry drives toward miniaturization and energy efficiency. However, practical SMPS design courses are seldom offered. In this paper, a generalized MATLAB/SIMULINK modeling technique is first presented. A proposed practical SMPS design course at…

  7. High-resolution interpolation of climate scenarios for Canada derived from general circulation model simulations

    Treesearch

    D. T. Price; D. W. McKenney; L. A. Joyce; R. M. Siltanen; P. Papadopol; K. Lawrence

    2011-01-01

    Projections of future climate were selected for four well-established general circulation models (GCMs) forced by each of three greenhouse gas (GHG) emissions scenarios recommended by the Intergovernmental Panel on Climate Change (IPCC), namely scenarios A2, A1B, and B1 of the IPCC Special Report on Emissions Scenarios. Monthly data for the period 1961-2100 were...

  8. Talker-identification training using simulations of binaurally combined electric and acoustic hearing: generalization to speech and emotion recognition.

    PubMed

    Krull, Vidya; Luo, Xin; Iler Kirk, Karen

    2012-04-01

    Understanding speech in background noise, talker identification, and vocal emotion recognition are challenging for cochlear implant (CI) users due to poor spectral resolution and limited pitch cues with the CI. Recent studies have shown that bimodal CI users, that is, those CI users who wear a hearing aid (HA) in their non-implanted ear, receive benefit for understanding speech both in quiet and in noise. This study compared the efficacy of talker-identification training in two groups of young normal-hearing adults, listening to either acoustic simulations of unilateral CI or bimodal (CI+HA) hearing. Training resulted in improved identification of talkers for both groups with better overall performance for simulated bimodal hearing. Generalization of learning to sentence and emotion recognition also was assessed in both subject groups. Sentence recognition in quiet and in noise improved for both groups, no matter if the talkers had been heard during training or not. Generalization to improvements in emotion recognition for two unfamiliar talkers also was noted for both groups with the simulated bimodal-hearing group showing better overall emotion-recognition performance. Improvements in sentence recognition were retained a month after training in both groups. These results have potential implications for aural rehabilitation of conventional and bimodal CI users.

  9. Talker-identification training using simulations of binaurally combined electric and acoustic hearing: Generalization to speech and emotion recognitiona

    PubMed Central

    Krull, Vidya; Luo, Xin; Iler Kirk, Karen

    2012-01-01

    Understanding speech in background noise, talker identification, and vocal emotion recognition are challenging for cochlear implant (CI) users due to poor spectral resolution and limited pitch cues with the CI. Recent studies have shown that bimodal CI users, that is, those CI users who wear a hearing aid (HA) in their non-implanted ear, receive benefit for understanding speech both in quiet and in noise. This study compared the efficacy of talker-identification training in two groups of young normal-hearing adults, listening to either acoustic simulations of unilateral CI or bimodal (CI+HA) hearing. Training resulted in improved identification of talkers for both groups with better overall performance for simulated bimodal hearing. Generalization of learning to sentence and emotion recognition also was assessed in both subject groups. Sentence recognition in quiet and in noise improved for both groups, no matter if the talkers had been heard during training or not. Generalization to improvements in emotion recognition for two unfamiliar talkers also was noted for both groups with the simulated bimodal-hearing group showing better overall emotion-recognition performance. Improvements in sentence recognition were retained a month after training in both groups. These results have potential implications for aural rehabilitation of conventional and bimodal CI users. PMID:22501080

  10. Thermal conductance of carbon nanotube contacts: Molecular dynamics simulations and general description of the contact conductance

    NASA Astrophysics Data System (ADS)

    Salaway, Richard N.; Zhigilei, Leonid V.

    2016-07-01

    The contact conductance of carbon nanotube (CNT) junctions is the key factor that controls the collective heat transfer through CNT networks or CNT-based materials. An improved understanding of the dependence of the intertube conductance on the contact structure and local environment is needed for predictive computational modeling or theoretical description of the effective thermal conductivity of CNT materials. To investigate the effect of local structure on the thermal conductance across CNT-CNT contact regions, nonequilibrium molecular dynamics (MD) simulations are performed for different intertube contact configurations (parallel fully or partially overlapping CNTs and CNTs crossing each other at different angles) and local structural environments characteristic of CNT network materials. The results of MD simulations predict a stronger CNT length dependence present over a broader range of lengths than has been previously reported and suggest that the effect of neighboring junctions on the conductance of CNT-CNT junctions is weak and only present when the CNTs that make up the junctions are within the range of direct van der Waals interaction with each other. A detailed analysis of the results obtained for a diverse range of intertube contact configurations reveals a nonlinear dependence of the conductance on the contact area (or number of interatomic intertube interactions) and suggests larger contributions to the conductance from areas of the contact where the density of interatomic intertube interactions is smaller. An empirical relation accounting for these observations and expressing the conductance of an arbitrary contact configuration through the total number of interatomic intertube interactions and the average number of interatomic intertube interactions per atom in the contact region is proposed. The empirical relation is found to provide a good quantitative description of the contact conductance for various CNT configurations investigated in the MD

  11. Benchmark simulation model no 2: general protocol and exploratory case studies.

    PubMed

    Jeppsson, U; Pons, M-N; Nopens, I; Alex, J; Copp, J B; Gernaey, K V; Rosen, C; Steyer, J-P; Vanrolleghem, P A

    2007-01-01

    Over a decade ago, the concept of objectively evaluating the performance of control strategies by simulating them using a standard model implementation was introduced for activated sludge wastewater treatment plants. The resulting Benchmark Simulation Model No 1 (BSM1) has been the basis for a significant new development that is reported on here: Rather than only evaluating control strategies at the level of the activated sludge unit (bioreactors and secondary clarifier) the new BSM2 now allows the evaluation of control strategies at the level of the whole plant, including primary clarifier and sludge treatment with anaerobic sludge digestion. In this contribution, the decisions that have been made over the past three years regarding the models used within the BSM2 are presented and argued, with particular emphasis on the ADM1 description of the digester, the interfaces between activated sludge and digester models, the included temperature dependencies and the reject water storage. BSM2-implementations are now available in a wide range of simulation platforms and a ring test has verified their proper implementation, consistent with the BSM2 definition. This guarantees that users can focus on the control strategy evaluation rather than on modelling issues. Finally, for illustration, twelve simple operational strategies have been implemented in BSM2 and their performance evaluated. Results show that it is an interesting control engineering challenge to further improve the performance of the BSM2 plant (which is the whole idea behind benchmarking) and that integrated control (i.e. acting at different places in the whole plant) is certainly worthwhile to achieve overall improvement.

  12. A general aviation simulator evaluation of a rate-enhanced instrument landing system display

    NASA Technical Reports Server (NTRS)

    Hinton, D. A.

    1981-01-01

    A piloted-simulation study was conducted to evaluate the effect on instrument landing system tracking performance of integrating localizer-error rate with raw localizer and glide-slope error. The display was named the pseudocommand tracking indicator (PCTI) because it provides an indication of the change of heading required to track the localizer center line. Eight instrument-rated pilots each flew five instrument approaches with the PCTI and five instrument approaches with a conventional course deviation indicator. The results show good overall pilot acceptance of the display, a significant improvement in localizer tracking error, and no significant changes in glide-slope tracking error or pilot workload.

  13. Different parameters support generalization and discrimination learning in Drosophila at the flight simulator.

    PubMed

    Brembs, Björn; Hempel de Ibarra, Natalie

    2006-01-01

    We have used a genetically tractable model system, the fruit fly Drosophila melanogaster to study the interdependence between sensory processing and associative processing on learning performance. We investigated the influence of variations in the physical and predictive properties of color stimuli in several different operant-conditioning procedures on the subsequent learning performance. These procedures included context and stimulus generalization as well as color, compound, and conditional discrimination (colors and patterns). A surprisingly complex dependence of the learning performance on the colors' physical and predictive properties emerged, which was clarified by taking into account the fly-subjective perception of the color stimuli. Based on estimates of the stimuli's color and brightness values, we propose that the different tasks are supported by different parameters of the color stimuli; generalization occurs only if the chromaticity is sufficiently similar, whereas discrimination learning relies on brightness differences.

  14. Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a mean-field magnetic dynamo

    NASA Astrophysics Data System (ADS)

    Sądowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Abarca, David; Zhu, Yucong; McKinney, Jonathan C.

    2015-02-01

    We present a mean-field model that emulates the magnetic dynamo operating in magnetized accretion discs. We have implemented this model in the general relativisic radiation magnetohydrodynamic (GRRMHD) code KORAL, using results from local shearing sheet simulations of the magnetorotational instability to fix the parameters of the dynamo. With the inclusion of this dynamo, we are able to run 2D axisymmetric GRRMHD simulations of accretion discs for arbitrarily long times. The simulated discs exhibit sustained turbulence, with the poloidal and toroidal magnetic field components driven towards a state similar to that seen in 3D studies. Using this dynamo code, we present a set of long-duration global simulations of super-Eddington, optically thick discs around non-spinning and spinning black holes. Super-Eddington discs around non-rotating black holes exhibit a surprisingly large efficiency, η ≈ 0.04, independent of the accretion rate, where we measure efficiency in terms of the total energy output, both radiation and mechanical, flowing out to infinity. This value significantly exceeds the efficiency predicted by slim disc models for these accretion rates. Super-Eddington discs around spinning black holes are even more efficient, and appear to extract black hole rotational energy through a process similar to the Blandford-Znajek mechanism. All the simulated models are characterized by highly super-Eddington radiative fluxes collimated along the rotation axis. We also present a set of simulations that were designed to have Eddington or slightly sub-Eddington accretion rates (dot{M} ≲ 2dot{M}_Edd). None of these models reached a steady state. Instead, the discs collapsed as a result of runaway cooling, presumably because of a thermal instability.

  15. Proficiency in cardiopulmonary resuscitation of medical students at graduation: a simulator-based comparison with general practitioners.

    PubMed

    Lüscher, Fabian; Hunziker, Sabina; Gaillard, Vincent; Tschan, Franzisks; Semmer, Norbert K; Hunziker, Patrick R; Marsch, Stephan

    2010-01-23

    There are no data on the preparedness of medical students at the time of their graduation to handle a cardiac arrest. The aim of the present study was to compare the performance in cardiopulmonary resuscitation of medical students at the time of their graduation with that of experienced general practitioners. 24 teams consisting of three medical students and 24 teams consisting of three general practitioners were confronted with a scenario of a simulated witnessed cardiac arrest. Analysis was performed post-hoc using video recordings obtained during the simulation. Medical students diagnosed the cardiac arrest as quickly as general practitioners. Medical students were less likely to call for help in the initial phase of the cardiac arrest (14/24 vs 21/24; P = 0.002); had less hands-on time during the first 180 seconds of the arrest (52 +/- 33 sec vs 105 +/- 39 sec; P <0.0001); delayed the first defibrillation (168 +/- 78 vs 116 +/- 46 sec, P <0.007); and showed less directive leadership (4/24 vs 14/24 teams, P <0.007). The technical quality of cardiopulmonary resuscitation provided by medical students was partly better, but for no parameter worse, than that provided by general practitioners. When confronted with a cardiac arrest, medical students at the time of their graduation substantially delayed evidence-based life-saving measures like defibrillation and provided only half of the resuscitation support provided by experienced general practitioners. Future research should focus on how to best prepare medical students to handle medical emergencies.

  16. A general approach to develop reduced order models for simulation of solid oxide fuel cell stacks

    SciTech Connect

    Pan, Wenxiao; Bao, Jie; Lo, Chaomei; Lai, Canhai; Agarwal, Khushbu; Koeppel, Brian J.; Khaleel, Mohammad A.

    2013-06-15

    A reduced order modeling approach based on response surface techniques was developed for solid oxide fuel cell stacks. This approach creates a numerical model that can quickly compute desired performance variables of interest for a stack based on its input parameter set. The approach carefully samples the multidimensional design space based on the input parameter ranges, evaluates a detailed stack model at each of the sampled points, and performs regression for selected performance variables of interest to determine the responsive surfaces. After error analysis to ensure that sufficient accuracy is established for the response surfaces, they are then implemented in a calculator module for system-level studies. The benefit of this modeling approach is that it is sufficiently fast for integration with system modeling software and simulation of fuel cell-based power systems while still providing high fidelity information about the internal distributions of key variables. This paper describes the sampling, regression, sensitivity, error, and principal component analyses to identify the applicable methods for simulating a planar fuel cell stack.

  17. SciDAC - Center for Simulation of Wave Interactions with MHD -- General Atomics Support of ORNL Collaboration

    SciTech Connect

    Abla, G

    2012-11-09

    The Center for Simulation of Wave Interactions with Magnetohydrodynamics (SWIM) project is dedicated to conduct research on integrated multi-physics simulations. The Integrated Plasma Simulator (IPS) is a framework that was created by the SWIM team. It provides an integration infrastructure for loosely coupled component-based simulations by facilitating services for code execution coordination, computational resource management, data management, and inter-component communication. The IPS framework features improving resource utilization, implementing application-level fault tolerance, and support of the concurrent multi-tasking execution model. The General Atomics (GA) team worked closely with other team members on this contract, and conducted research in the areas of computational code monitoring, meta-data management, interactive visualization, and user interfaces. The original website to monitor SWIM activity was developed in the beginning of the project. Due to the amended requirements, the software was redesigned and a revision of the website was deployed into production in April of 2010. Throughout the duration of this project, the SWIM Monitoring Portal (http://swim.gat.com:8080/) has been a critical production tool for supporting the project's physics goals.

  18. Structuring energy supply and demand networks in a general equilibrium model to simulate global warming control strategies

    SciTech Connect

    Hamilton, S.; Veselka, T.D.; Cirillo, R.R.

    1991-01-01

    Global warming control strategies which mandate stringent caps on emissions of greenhouse forcing gases can substantially alter a country's demand, production, and imports of energy products. Although there is a large degree of uncertainty when attempting to estimate the potential impact of these strategies, insights into the problem can be acquired through computer model simulations. This paper presents one method of structuring a general equilibrium model, the ENergy and Power Evaluation Program/Global Climate Change (ENPEP/GCC), to simulate changes in a country's energy supply and demand balance in response to global warming control strategies. The equilibrium model presented in this study is based on the principle of decomposition, whereby a large complex problem is divided into a number of smaller submodules. Submodules simulate energy activities and conversion processes such as electricity production. These submodules are linked together to form an energy supply and demand network. Linkages identify energy and fuel flows among various activities. Since global warming control strategies can have wide reaching effects, a complex network was constructed. The network represents all energy production, conversion, transportation, distribution, and utilization activities. The structure of the network depicts interdependencies within and across economic sectors and was constructed such that energy prices and demand responses can be simulated. Global warming control alternatives represented in the network include: (1) conservation measures through increased efficiency; and (2) substitution of fuels that have high greenhouse gas emission rates with fuels that have lower emission rates. 6 refs., 4 figs., 4 tabs.

  19. Sea ice simulations based on fields generated by the GLAS GCM. [Goddard Laboratory for Atmospheric Sciences General Circulation Model

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Herman, G. F.

    1980-01-01

    The GLAS General Circulation Model (GCM) was applied to the four-month simulation of the thermodynamic part of the Parkinson-Washington sea ice model using atmospheric boundary conditions. The sea ice thickness and distribution were predicted for the Jan. 1-Apr. 30 period using the GCM-fields of solar and infrared radiation, specific humidity and air temperature at the surface, and snow accumulation; the sensible heat and evaporative surface fluxes were consistent with the ground temperatures produced by the ice model and the air temperatures determined by the atmospheric concept. It was concluded that the Parkinson-Washington sea ice model results in acceptable ice concentrations and thicknesses when used with GLAS GCM for the Jan.-Apr. period suggesting the feasibility of fully coupled ice-atmosphere simulations with these two approaches.

  20. Simulation of swimming of a flexible filament using the generalized lattice-spring lattice-Boltzmann method.

    PubMed

    Wu, Tai-Hsien; Guo, Rurng-Sheng; He, Guo-Wei; Liu, Ying-Ming; Qi, Dewei

    2014-05-21

    A generalized lattice-spring lattice-Boltzmann model (GLLM) is introduced by adding a three-body force in the traditional lattice-spring model. This method is able to deal with bending deformation of flexible biological bodies in fluids. The interactions between elastic solids and fluid are treated with the immersed boundary-lattice Boltzmann method. GLLM is validated by comparing the present results with the existing theoretical and simulation results. As an application of GLLM, swimming of flagellum in fluid is simulated and propulsive force as a function of driven frequency and fluid structures at various Reynolds numbers 0.15-5.1 are presented in this paper. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Christmas: an event driven by our hormones?

    PubMed

    Ludwig, M

    2011-12-01

    No other event in the Christian calendar has such a deep impact on our behaviour as the annual event called Christmas. Christmas is not just 'Christmas Day'; indeed, it is a long developmental rhythm with a period of almost exactly 365 days. Here, I describe the neuronal and hormonal changes and their effects on our behaviour during the preparation and the execution of the event(1) . © 2011 The Author. Journal of Neuroendocrinology © 2011 Blackwell Publishing Ltd.

  2. TOUGH2: A general-purpose numerical simulator for multiphase fluid and heat flow

    SciTech Connect

    Pruess, K.

    1991-05-01

    TOUGH2 is a numerical simulation program for nonisothermal flows of multicomponent, multiphase fluids in porous and fractured media. The chief applications for which TOUGH2 is designed are in geothermal reservoir engineering, nuclear waste disposal, and unsaturated zone hydrology. A successor to the TOUGH program, TOUGH2 offers added capabilities and user features, including the flexibility to handle different fluid mixtures, facilities for processing of geometric data (computational grids), and an internal version control system to ensure referenceability of code applications. This report includes a detailed description of governing equations, program architecture, and user features. Enhancements in data inputs relative to TOUGH are described, and a number of sample problems are given to illustrate code applications. 46 refs., 29 figs., 12 tabs.

  3. Generalized Metropolis acceptance criterion for hybrid non-equilibrium molecular dynamics-Monte Carlo simulations.

    PubMed

    Chen, Yunjie; Roux, Benoît

    2015-01-14

    A family of hybrid simulation methods that combines the advantages of Monte Carlo (MC) with the strengths of classical molecular dynamics (MD) consists in carrying out short non-equilibrium MD (neMD) trajectories to generate new configurations that are subsequently accepted or rejected via an MC process. In the simplest case where a deterministic dynamic propagator is used to generate the neMD trajectories, the familiar Metropolis acceptance criterion based on the change in the total energy ΔE, min[1, exp{-βΔE}], guarantees that the hybrid algorithm will yield the equilibrium Boltzmann distribution. However, the functional form of the acceptance probability is more complex when the non-equilibrium switching process is generated via a non-deterministic stochastic dissipative propagator coupled to a heat bath. Here, we clarify the conditions under which the Metropolis criterion remains valid to rigorously yield a proper equilibrium Boltzmann distribution within hybrid neMD-MC algorithm.

  4. General treatment of spatial light modulator dead-zone effects on optical correlation. 1. Computer simulations

    NASA Astrophysics Data System (ADS)

    Woods, C. L.; Gianino, P. D.

    1993-11-01

    In this article the authors present an approximate mathematical analysis and exact computer simulations for optical correlation in correlators having pixellated spatial light modulators with transmissive (or reflective) dead zones in both the input and filter planes. Results of this study show that the correlation amplitude consists of four terms: a true correlation plus three different types of noise terms originating from the transmissive dead zones in both spatial light modulators: the authors describe the role that each of these terms plays in the correlation process. In addition the authors calculate peak intensity, signal-to-noise ratio, and energy throughput efficiency as a function of dead-zone area in both spatial light modulators using either phase-only or matched filters.

  5. CO adsorption over Pd nanoparticles: A general framework for IR simulations on nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeinalipour-Yazdi, Constantinos D.; Willock, David J.; Thomas, Liam; Wilson, Karen; Lee, Adam F.

    2016-04-01

    CO vibrational spectra over catalytic nanoparticles under high coverages/pressures are discussed from a DFT perspective. Hybrid B3LYP and PBE DFT calculations of CO chemisorbed over Pd4 and Pd13 nanoclusters, and a 1.1 nm Pd38 nanoparticle, have been performed in order to simulate the corresponding coverage dependent infrared (IR) absorption spectra, and hence provide a quantitative foundation for the interpretation of experimental IR spectra of CO over Pd nanocatalysts. B3LYP simulated IR intensities are used to quantify site occupation numbers through comparison with experimental DRIFTS spectra, allowing an atomistic model of CO surface coverage to be created. DFT adsorption energetics for low CO coverage (θ → 0) suggest the CO binding strength follows the order hollow > bridge > linear, even for dispersion-corrected functionals for sub-nanometre Pd nanoclusters. For a Pd38 nanoparticle, hollow and bridge-bound are energetically similar (hollow ≈ bridge > atop). It is well known that this ordering has not been found at the high coverages used experimentally, wherein atop CO has a much higher population than observed over Pd(111), confirmed by our DRIFTS spectra for Pd nanoparticles supported on a KIT-6 silica, and hence site populations were calculated through a comparison of DFT and spectroscopic data. At high CO coverage (θ = 1), all three adsorbed CO species co-exist on Pd38, and their interdiffusion is thermally feasible at STP. Under such high surface coverages, DFT predicts that bridge-bound CO chains are thermodynamically stable and isoenergetic to an entirely hollow bound Pd/CO system. The Pd38 nanoparticle undergoes a linear (3.5%), isotropic expansion with increasing CO coverage, accompanied by 63 and 30 cm- 1 blue-shifts of hollow and linear bound CO respectively.

  6. Interannual tropical rainfall variability in general circulation model simulations associated with the atmospheric model intercomparison project

    SciTech Connect

    Sperber, K.R.; Palmer, T.N.

    1996-11-01

    The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 models for the period 1979 - 88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each model. This subset of models also had a rainfall climatology that was in better agreement with observations, indicating a link between systematic model error and the ability to simulate interannual variations. A suite of six European Centre for Medium-Range Weather Forecasts (ECMWF) AMIP runs (differing only in their initial conditions) have also been examined. As observed, all-India rainfall was enhanced in 1988 relative to 1987 in each of these realizations. All-India rainfall variability during other years showed little or no predictability, possibly due to internal chaotic dynamics associated with intraseasonal monsoon fluctuations and/or unpredictable land surface process interactions. The interannual variations of Nordeste rainfall were best represented. The State University of New York at Albany /National Center for Atmospheric Research Genesis model was run in five initial condition realizations. In this model, the Nordeste rainfall variability was also best reproduced. However, for all regions the skill was less than that of the ECMWF model. The relationships of the all-India and Sahel rainfall/SST teleconnections with horizontal resolution, convection scheme closure, and numerics have been evaluated. 64 refs., 13 figs., 3 tabs.

  7. General Relativistic Hydrodynamic Simulation of Accretion Flow from a Stellar Tidal Disruption

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka; Krolik, Julian H.; Cheng, Roseanne M.; Piran, Tsvi; Noble, Scott C.

    2015-05-01

    We study how the matter dispersed when a supermassive black hole tidally disrupts a star joins an accretion flow. Combining a relativistic hydrodynamic simulation of the stellar disruption with a relativistic hydrodynamics simulation of the subsequent debris motion, we track the evolution of such a system until ≃ 80% of the stellar mass bound to the black hole has settled into an accretion flow. Shocks near the stellar pericenter and also near the apocenter of the most tightly bound debris dissipate orbital energy, but only enough to make its characteristic radius comparable to the semimajor axis of the most bound material, not the tidal radius as previously envisioned. The outer shocks are caused by post-Newtonian relativistic effects, both on the stellar orbit during its disruption and on the tidal forces. Accumulation of mass into the accretion flow is both non-monotonic and slow, requiring several to 10 times the orbital period of the most tightly bound tidal streams, while the inflow time for most of the mass may be comparable to or longer than the mass accumulation time. Deflection by shocks does, however, cause some mass to lose both angular momentum and energy, permitting it to move inward even before most of the mass is accumulated into the accretion flow. Although the accretion rate still rises sharply and then decays roughly as a power law, its maximum is ≃ 0.1× the previous expectation, and the timescale of the peak is ≃ 5× longer than previously predicted. The geometric mean of the black hole mass and stellar mass inferred from a measured event timescale is therefore ≃ 0.2× the value given by classical theory.

  8. Finite element for rotor/stator interactive forces in general engine dynamic simulation. Part 1: Development of bearing damper element

    NASA Technical Reports Server (NTRS)

    Adams, M. L.; Padovan, J.; Fertis, D. G.

    1980-01-01

    A general purpose squeeze-film damper interactive force element was developed, coded into a software package (module) and debugged. This software package was applied to nonliner dynamic analyses of some simple rotor systems. Results for pressure distributions show that the long bearing (end sealed) is a stronger bearing as compared to the short bearing as expected. Results of the nonlinear dynamic analysis, using a four degree of freedom simulation model, showed that the orbit of the rotating shaft increases nonlinearity to fill the bearing clearance as the unbalanced weight increases.

  9. Simulating coarse-scale vegetation dynamics using the Columbia River Basin succession model-crbsum. Forest Service general technical report

    SciTech Connect

    Keane, R.E.; Long, D.G.; Menakis, J.P.; Hann, W.J.; Bevins, C.D.

    1996-10-01

    The paper details the landscape succession model developed for the coarse-scale assessment called CRBSUM (Columbia River Basin SUccession Model) and presents some general results of the application of this model to the entire basin. CRBSUM was used to predict future landscape characteristics to evaluate management alternatives for both mid-and coarse-scale efforts. A test and sensitivity analysis of CRBSUM is also presented. This paper was written as a users guide for those who wish to run the model and interprete results, and its was also written as documentation for some results of the Interior Columbia River Basin simulation effort.

  10. The r-process in black hole-neutron star mergers based on a fully general-relativistic simulation

    NASA Astrophysics Data System (ADS)

    Nishimura, N.; Wanajo, S.; Sekiguchi, Y.; Kiuchi, K.; Kyutoku, K.; Shibata, M.

    2016-01-01

    We investigate the black hole-neutron star binary merger in the contest of the r-process nucleosynthesis. Employing a hydrodynamical model simulated in the framework of full general relativity, we perform nuclear reaction network calculations. The extremely neutron-rich matter with the total mass 0.01 M⊙ is ejected, in which a strong r-process with fission cycling proceeds due to the high neutron number density. We discuss relevant astrophysical issues such as the origin of r-process elements as well as the r-process powered electromagnetic transients.

  11. Modelling uncertainty in incompressible flow simulation using Galerkin based generalized ANOVA

    NASA Astrophysics Data System (ADS)

    Chakraborty, Souvik; Chowdhury, Rajib

    2016-11-01

    This paper presents a new algorithm, referred to here as Galerkin based generalized analysis of variance decomposition (GG-ANOVA) for modelling input uncertainties and its propagation in incompressible fluid flow. The proposed approach utilizes ANOVA to represent the unknown stochastic response. Further, the unknown component functions of ANOVA are represented using the generalized polynomial chaos expansion (PCE). The resulting functional form obtained by coupling the ANOVA and PCE is substituted into the stochastic Navier-Stokes equation (NSE) and Galerkin projection is employed to decompose it into a set of coupled deterministic 'Navier-Stokes alike' equations. Temporal discretization of the set of coupled deterministic equations is performed by employing Adams-Bashforth scheme for convective term and Crank-Nicolson scheme for diffusion term. Spatial discretization is performed by employing finite difference scheme. Implementation of the proposed approach has been illustrated by two examples. In the first example, a stochastic ordinary differential equation has been considered. This example illustrates the performance of proposed approach with change in nature of random variable. Furthermore, convergence characteristics of GG-ANOVA has also been demonstrated. The second example investigates flow through a micro channel. Two case studies, namely the stochastic Kelvin-Helmholtz instability and stochastic vortex dipole, have been investigated. For all the problems results obtained using GG-ANOVA are in excellent agreement with benchmark solutions.

  12. Generalized Eddington analytical model for azimuthally dependent radiance simulation in stratified media.

    PubMed

    Marzano, Frank S; Ferrauto, Giancarlo

    2005-10-01

    A fast analytical radiative transfer model to account for propagation of unpolarized monochromatic radiation in random media with a plane-parallel geometry is presented. The model employs an Eddington-like approach combined with the delta phase-function transformation technique. The Eddington approximation is extended in a form that allows us to unfold the azimuthal dependence of the radiance field. A first-order scattering correction to the azimuth-dependent Eddington radiative model solution is also performed to improve the model accuracy for low-scattering media and flexibility with respect to use of explicit arbitrary phase functions. The first-order scattering-corrected solution, called the generalized Eddington radiative model (GERM), is systematically tested against a numerical multistream discrete ordinate model for backscattered radiance at the top of the medium. The typical mean accuracy of the GERM solution is generally better than 10% with a standard deviation of 20% for radiance calculations over a wide range of independent input optical parameters and observation angles. GERM errors are shown to be comparable with the errors due to an input parameter uncertainty of precise numerical models. The proposed model can be applied in a quite arbitrary random medium, and the results are appealing in all cases where speed, accuracy, and/or closed-form solutions are requested. Its potentials, limitations, and further extensions are discussed.

  13. Generalized fictitious methods for fluid-structure interactions: Analysis and simulations

    NASA Astrophysics Data System (ADS)

    Yu, Yue; Baek, Hyoungsu; Karniadakis, George Em

    2013-07-01

    We present a new fictitious pressure method for fluid-structure interaction (FSI) problems in incompressible flow by generalizing the fictitious mass and damping methods we published previously in [1]. The fictitious pressure method involves modification of the fluid solver whereas the fictitious mass and damping methods modify the structure solver. We analyze all fictitious methods for simplified problems and obtain explicit expressions for the optimal reduction factor (convergence rate index) at the FSI interface [2]. This analysis also demonstrates an apparent similarity of fictitious methods to the FSI approach based on Robin boundary conditions, which have been found to be very effective in FSI problems. We implement all methods, including the semi-implicit Robin based coupling method, in the context of spectral element discretization, which is more sensitive to temporal instabilities than low-order methods. However, the methods we present here are simple and general, and hence applicable to FSI based on any other spatial discretization. In numerical tests, we verify the selection of optimal values for the fictitious parameters for simplified problems and for vortex-induced vibrations (VIV) even at zero mass ratio ("for-ever-resonance"). We also develop an empirical a posteriori analysis for complex geometries and apply it to 3D patient-specific flexible brain arteries with aneurysms for very large deformations. We demonstrate that the fictitious pressure method enhances stability and convergence, and is comparable or better in most cases to the Robin approach or the other fictitious methods.

  14. Simulation

    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.

  15. Mars atmospheric dynamics as simulated by the NASA Ames General Circulation Model. I - The zonal-mean circulation

    NASA Technical Reports Server (NTRS)

    Haberle, Robert M.; Pollack, James B.; Barnes, Jeffrey R.; Zurek, Richard W.; Leovy, Conway B.; Murphy, James R.; Lee, Hilda; Schaeffer, James

    1993-01-01

    The characteristics of the zonal-mean circulation and how it responds to seasonal variations and dust loading are described. This circulation is the main momentum-containing component of the general circulation, and it plays a dominant role in the budgets of heat and momentum. It is shown that in many ways the zonal-mean circulation on Mars, at least as simulated by the model, is similar to that on earth, having Hadley and Ferrel cells and high-altitude jet streams. However, the Martian systems tend to be deeper, more intense, and much more variable with season. Furthermore, the radiative effects of suspended dust particles, even in small amounts, have a major influence on the general circulation.

  16. Generalized three-dimensional simulation of ferruled coupled-cavity traveling-wave-tube dispersion and impedance characteristics

    NASA Technical Reports Server (NTRS)

    Maruschek, Joseph W.; Kory, Carol L.; Wilson, Jeffrey D.

    1993-01-01

    The frequency-phase dispersion and Pierce on-axis interaction impedance of a ferruled, coupled-cavity, traveling-wave tube (TWT), slow-wave circuit were calculated using the three-dimensional simulation code Micro-SOS. The utilization of the code to reduce costly and time-consuming experimental cold tests is demonstrated by the accuracy achieved in calculating these parameters. A generalized input file was developed so that ferruled coupled-cavity TWT slow-wave circuits of arbitrary dimensions could be easily modeled. The practicality of the generalized input file was tested by applying it to the ferruled coupled-cavity slow-wave circuit of the Hughes Aircraft Company model 961HA TWT and by comparing the results with experimental results.

  17. Generalized versus patient-specific inflow boundary conditions in computational fluid dynamics simulations of cerebral aneurysmal hemodynamics.

    PubMed

    Jansen, I G H; Schneiders, J J; Potters, W V; van Ooij, P; van den Berg, R; van Bavel, E; Marquering, H A; Majoie, C B L M

    2014-08-01

    Attempts have been made to associate intracranial aneurysmal hemodynamics with aneurysm growth and rupture status. Hemodynamics in aneurysms is traditionally determined with computational fluid dynamics by using generalized inflow boundary conditions in a parent artery. Recently, patient-specific inflow boundary conditions are being implemented more frequently. Our purpose was to compare intracranial aneurysm hemodynamics based on generalized versus patient-specific inflow boundary conditions. For 36 patients, geometric models of aneurysms were determined by using 3D rotational angiography. 2D phase-contrast MR imaging velocity measurements of the parent artery were performed. Computational fluid dynamics simulations were performed twice: once by using patient-specific phase-contrast MR imaging velocity profiles and once by using generalized Womersley profiles as inflow boundary conditions. Resulting mean and maximum wall shear stress and oscillatory shear index values were analyzed, and hemodynamic characteristics were qualitatively compared. Quantitative analysis showed statistically significant differences for mean and maximum wall shear stress values between both inflow boundary conditions (P < .001). Qualitative assessment of hemodynamic characteristics showed differences in 21 cases: high wall shear stress location (n = 8), deflection location (n = 3), lobulation wall shear stress (n = 12), and/or vortex and inflow jet stability (n = 9). The latter showed more instability for the generalized inflow boundary conditions in 7 of 9 patients. Using generalized and patient-specific inflow boundary conditions for computational fluid dynamics results in different wall shear stress magnitudes and hemodynamic characteristics. Generalized inflow boundary conditions result in more vortices and inflow jet instabilities. This study emphasizes the necessity of patient-specific inflow boundary conditions for calculation of hemodynamics in cerebral aneurysms by using

  18. Modeling Two-Phase Flow and Vapor Cycles Using the Generalized Fluid System Simulation Program

    NASA Technical Reports Server (NTRS)

    Smith, Amanda D.; Majumdar, Alok K.

    2017-01-01

    This work presents three new applications for the general purpose fluid network solver code GFSSP developed at NASA's Marshall Space Flight Center: (1) cooling tower, (2) vapor-compression refrigeration system, and (3) vapor-expansion power generation system. These systems are widely used across engineering disciplines in a variety of energy systems, and these models expand the capabilities and the use of GFSSP to include fluids and features that are not part of its present set of provided examples. GFSSP provides pressure, temperature, and species concentrations at designated locations, or nodes, within a fluid network based on a finite volume formulation of thermodynamics and conservation laws. This paper describes the theoretical basis for the construction of the models, their implementation in the current GFSSP modeling system, and a brief evaluation of the usefulness of the model results, as well as their applicability toward a broader spectrum of analytical problems in both university teaching and engineering research.

  19. Simulation of the thermospheric tides by use of the NCAR thermospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Fensen, C. G.; Dickinson, R. E.; Roble, R. G.

    1986-01-01

    Numerical calculations of the thermospheric tidal winds and temperatures at equinox are presented. The calculations were made using the National Center for Atmospheric Research Thermospheric General Circulation Model (TGCM), which includes the effects of viscosity, conductivity, diffusion, ion drag, winds, and temperature gradients. The thermospheric diurnal and semidiurnal tides are excited in situ by solar heating and by ion-neutral momentum coupling. The semidiurnal tidal calculations also include the effects of upward propagating waves generated by heating in the lower atmosphere. This semidiurnal propagating component is modeled by use of the classical tidal perturbations as lower boundary conditions. The model is tuned by adjusting the propagating tidal forcing term until calculated semidiurnal wind and temperature fields best approximate incoherent scatter observations. The tidal TGCM results are consistent with previous theoretical work and successfully reproduce high altitude temperature and meridional velocity data, but they give significantly lower magnitudes for velocities and temperatures near 160 km than are seen by observations.

  20. Generalized Modelling of the Stabilizer Link and Static Simulation Using FEM

    NASA Astrophysics Data System (ADS)

    Cofaru, Nicolae Florin; Roman, Lucian Ion; Oleksik, Valentin; Pascu, Adrian

    2016-12-01

    This paper proposes an organological approach of one of the components of front suspension, namely anti-roll power link. There will be realized a CAD 3D modelling of this power link. 3D modelling is generalized and there were used the powers of Catia V5R20 software. Parameterized approach provides a high flexibility in the design, meaning that dimensional and shape changes of the semi-power link are very easy to perform just by changing some parameters. Several new versions are proposed for the anti-roll power link body. At the end of the work, it is made a static analysis of the semi-power link model used in the suspension of vehicles OPEL ASTRA G, ZAFIRA, MERIVA, and constructive optimization of its body.

  1. 3D Simulations of the Early Mars Climate with a General Circulation Model

    NASA Technical Reports Server (NTRS)

    Forget, F.; Haberle, R. M.; Montmessin, F.; Cha, S.; Marcq, E.; Schaeffer, J.; Wanherdrick, Y.

    2003-01-01

    The environmental conditions that existed on Mars during the Noachian period are subject to debate in the community. In any case, there are compelling evidence that these conditions were different than what they became later in the amazonian and possibly the Hesperian periods. Indeed, most of the old cratered terrains are disected by valley networks (thought to have been carved by flowing liquid water), whereas younger surface are almost devoid of such valleys. In addition, there are evidence that the erosion rate was much higher during the early noachian than later. Flowing water is surprising on early Mars because the solar luminosity was significantly lower than today. Even with the thick atmosphere (up to several bars).To improve our understanding of the early Mars Climate, we have developed a 3D general circulation model similar to the one used on current Earth or Mars to study the details of the climate today. Our first objective is to answer the following questions : how is the Martian climate modified if 1) the surface pressure is increased up to several bars (our baseline: 2 bars) and 2) if the sun luminosity is decreased by 25 account the heat possibly released by impacts during short periods, although it may have played a role .For this purpose, we have coupled the Martian General Circulation model developed at LMD with a sophisticated correlated k distribution model developped at NASA Ames Research Center. It is a narrow band model which computes the radiative transfer at both solar and thermal wavelengths (from 0.3 to 250 microns).

  2. Domain-general neural correlates of dependency formation: Using complex tones to simulate language.

    PubMed

    Brilmayer, Ingmar; Sassenhagen, Jona; Bornkessel-Schlesewsky, Ina; Schlesewsky, Matthias

    2017-08-01

    There is an ongoing debate whether the P600 event-related potential component following syntactic anomalies reflects syntactic processes per se, or if it is an instance of the P300, a domain-general ERP component associated with attention and cognitive reorientation. A direct comparison of both components is challenging because of the huge discrepancy in experimental designs and stimulus choice between language and 'classic' P300 experiments. In the present study, we develop a new approach to mimic the interplay of sequential position as well as categorical and relational information in natural language syntax (word category and agreement) in a non-linguistic target detection paradigm using musical instruments. Participants were instructed to (covertly) detect target tones which were defined by instrument change and pitch rise between subsequent tones at the last two positions of four-tone sequences. We analysed the EEG using event-related averaging and time-frequency decomposition. Our results show striking similarities to results obtained from linguistic experiments. We found a P300 that showed sensitivity to sequential position and a late positivity sensitive to stimulus type and position. A time-frequency decomposition revealed significant effects of sequential position on the theta band and a significant influence of stimulus type on the delta band. Our results suggest that the detection of non-linguistic targets defined via complex feature conjunctions in the present study and the detection of syntactic anomalies share the same underlying processes: attentional shift and memory based matching processes that act upon multi-feature conjunctions. We discuss the results as supporting domain-general accounts of the P600 during natural language comprehension. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Simulator study of a pictorial display for general aviation instrument flight

    NASA Technical Reports Server (NTRS)

    Adams, J. J.

    1982-01-01

    A simulation study of a computer drawn pictorial display involved a flight task that included an en route segment, terminal area maneuvering, a final approach, a missed approach, and a hold. The pictorial display consists of the drawing of boxes which either move along the desired path or are fixed at designated way points. Two boxes may be shown at all times, one related to the active way point and the other related to the standby way point. Ground tracks and vertical profiles of the flights, time histories of the final approach, and comments were obtained from time pilots. The results demonstrate the accuracy and consistency with which the segments of the flight are executed. The pilots found that the display is easy to learn and to use; that it provides good situation awareness, and that it could improve the safety of flight. The small size of the display, the lack of numerical information on pitch, roll, and heading angles, and the lack of definition of the boundaries of the conventional glide slope and localizer areas were criticized.

  4. Generalized Metropolis acceptance criterion for hybrid non-equilibrium molecular dynamics—Monte Carlo simulations

    SciTech Connect

    Chen, Yunjie; Roux, Benoît

    2015-01-14

    A family of hybrid simulation methods that combines the advantages of Monte Carlo (MC) with the strengths of classical molecular dynamics (MD) consists in carrying out short non-equilibrium MD (neMD) trajectories to generate new configurations that are subsequently accepted or rejected via an MC process. In the simplest case where a deterministic dynamic propagator is used to generate the neMD trajectories, the familiar Metropolis acceptance criterion based on the change in the total energy ΔE, min[1,  exp( − βΔE)], guarantees that the hybrid algorithm will yield the equilibrium Boltzmann distribution. However, the functional form of the acceptance probability is more complex when the non-equilibrium switching process is generated via a non-deterministic stochastic dissipative propagator coupled to a heat bath. Here, we clarify the conditions under which the Metropolis criterion remains valid to rigorously yield a proper equilibrium Boltzmann distribution within hybrid neMD-MC algorithm.

  5. A Second Law Based Unstructured Finite Volume Procedure for Generalized Flow Simulation

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok

    1998-01-01

    An unstructured finite volume procedure has been developed for steady and transient thermo-fluid dynamic analysis of fluid systems and components. The procedure is applicable for a flow network consisting of pipes and various fittings where flow is assumed to be one dimensional. It can also be used to simulate flow in a component by modeling a multi-dimensional flow using the same numerical scheme. The flow domain is discretized into a number of interconnected control volumes located arbitrarily in space. The conservation equations for each control volume account for the transport of mass, momentum and entropy from the neighboring control volumes. In addition, they also include the sources of each conserved variable and time dependent terms. The source term of entropy equation contains entropy generation due to heat transfer and fluid friction. Thermodynamic properties are computed from the equation of state of a real fluid. The system of equations is solved by a hybrid numerical method which is a combination of simultaneous Newton-Raphson and successive substitution schemes. The paper also describes the application and verification of the procedure by comparing its predictions with the analytical and numerical solution of several benchmark problems.

  6. Analog approach to mixed analog-digital circuit simulation

    NASA Astrophysics Data System (ADS)

    Ogrodzki, Jan

    2013-10-01

    Logic simulation of digital circuits is a well explored research area. Most up-to-date CAD tools for digital circuits simulation use an event driven, selective trace algorithm and Hardware Description Languages (HDL), e.g. the VHDL. This techniques enable simulation of mixed circuits, as well, where an analog part is connected to the digital one through D/A and A/D converters. The event-driven mixed simulation applies a unified, digital-circuits dedicated method to both digital and analog subsystems. In recent years HDL techniques have been also applied to mixed domains, as e.g. in the VHDL-AMS. This paper presents an approach dual to the event-driven one, where an analog part together with a digital one and with converters is treated as the analog subsystem and is simulated by means of circuit simulation techniques. In our problem an analog solver used yields some numerical problems caused by nonlinearities of digital elements. Efficient methods for overriding these difficulties have been proposed.

  7. Multiyear Simulations of the Martian Water Cycle with the Ames General Circulation Model

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Schaeffer, J. R.; Nelli, S. M.; Murphy, J. R.

    2003-01-01

    Mars atmosphere is carbon dioxide dominated with non-negligible amounts of water vapor and suspended dust particles. The atmospheric dust plays an important role in the heating and cooling of the planet through absorption and emission of radiation. Small dust particles can potentially be carried to great altitudes and affect the temperatures there. Water vapor condensing onto the dust grains can affect the radiative properties of both, as well as their vertical extent. The condensation of water onto a dust grain will change the grain s fall speed and diminish the possibility of dust obtaining high altitudes. In this capacity, water becomes a controlling agent with regard to the vertical distribution of dust. Similarly, the atmosphere s water vapor holding capacity is affected by the amount of dust in the atmosphere. Dust is an excellent green house catalyst; it raises the temperature of the atmosphere, and thus, its water vapor holding capacity. There is, therefore, a potentially significant interplay between the Martian dust and water cycles. Previous research done using global, 3-D computer modeling to better understand the Martian atmosphere treat the dust and the water cycles as two separate and independent processes. The existing Ames numerical model will be employed to simulate the relationship between the Martian dust and water cycles by actually coupling the two cycles. Water will condense onto the dust, allowing the particle's radiative characteristics, fall speeds, and as a result, their vertical distribution to change. Data obtained from the Viking, Mars Pathfinder, and especially the Mars Global Surveyor missions will be used to determine the accuracy of the model results.

  8. Simulating water with rigid non-polarizable models: a general perspective.

    PubMed

    Vega, Carlos; Abascal, Jose L F

    2011-11-28

    Over the last forty years many computer simulations of water have been performed using rigid non-polarizable models. Since these models describe water interactions in an approximate way it is evident that they cannot reproduce all of the properties of water. By now many properties for these kinds of models have been determined and it seems useful to compile some of these results and provide a critical view of the successes and failures. In this paper a test is proposed in which 17 properties of water, from the vapour and liquid to the solid phases, are taken into account to evaluate the performance of a water model. A certain number of points between zero (bad agreement) and ten (good agreement) are given for the predictions of each model and property. We applied the test to five rigid non-polarizable models, TIP3P, TIP5P, TIP4P, SPC/E and TIP4P/2005, obtaining an average score of 2.7, 3.7, 4.7, 5.1, and 7.2 respectively. Thus although no model reproduces all properties, some models perform better than others. It is clear that there are limitations for rigid non-polarizable models. Neglecting polarizability prevents an accurate description of virial coefficients, vapour pressures, critical pressure and dielectric constant. Neglecting nuclear quantum effects prevents an accurate description of the structure, the properties of water below 120 K and the heat capacity. It is likely that for rigid non-polarizable models it may not be possible to increase the score in the test proposed here beyond 7.6. To get closer to experiment, incorporating polarization and nuclear quantum effects is absolutely required even though a substantial increase in computer time should be expected. The test proposed here, being quantitative and selecting properties from all phases of water can be useful in the future to identify progress in the modelling of water.

  9. Noise in Neuronal and Electronic Circuits: A General Modeling Framework and Non-Monte Carlo Simulation Techniques.

    PubMed

    Kilinc, Deniz; Demir, Alper

    2017-08-01

    The brain is extremely energy efficient and remarkably robust in what it does despite the considerable variability and noise caused by the stochastic mechanisms in neurons and synapses. Computational modeling is a powerful tool that can help us gain insight into this important aspect of brain mechanism. A deep understanding and computational design tools can help develop robust neuromorphic electronic circuits and hybrid neuroelectronic systems. In this paper, we present a general modeling framework for biological neuronal circuits that systematically captures the nonstationary stochastic behavior of ion channels and synaptic processes. In this framework, fine-grained, discrete-state, continuous-time Markov chain models of both ion channels and synaptic processes are treated in a unified manner. Our modeling framework features a mechanism for the automatic generation of the corresponding coarse-grained, continuous-state, continuous-time stochastic differential equation models for neuronal variability and noise. Furthermore, we repurpose non-Monte Carlo noise analysis techniques, which were previously developed for analog electronic circuits, for the stochastic characterization of neuronal circuits both in time and frequency domain. We verify that the fast non-Monte Carlo analysis methods produce results with the same accuracy as computationally expensive Monte Carlo simulations. We have implemented the proposed techniques in a prototype simulator, where both biological neuronal and analog electronic circuits can be simulated together in a coupled manner.

  10. General dynamic properties of Abeta12-36 amyloid peptide involved in Alzheimer's disease from unfolding simulation.

    PubMed

    Suzuki, Shinya; Galzitskaya, Oxana V; Mitomo, Daisuke; Higo, Junichi

    2004-11-01

    To study the folding/unfolding properties of a beta-amyloid peptide Abeta(12-36) of Alzheimer's disease, five molecular dynamics simulations of Abeta(12-36) in explicit water were done at 450 K starting from a structure that is stable in trifluoroethanol/water at room temperature with two alpha-helices. Due to high temperature, the initial helical structure unfolded during the simulation. The observed aspects of the unfolding were as follows. 1) One helix (helix 1) had a longer life than the other (helix 2), which correlates well with the theoretically computed Phi values. 2) Temporal prolongation of helix 1 was found before unfolding. 3) Hydrophobic cores formed frequently with rearrangement of amino-acid residues in the hydrophobic cores. The formation and rearrangement of the hydrophobic cores may be a general aspect of this peptide in the unfolded state, and the structural changes accompanied by the hydrophobic-core rearrangement may lead the peptide to the most stable structure. 4) Concerted motions (collective modes) appeared to unfold helix 1. The collective modes were similar with those observed in another simulation at 300 K. The analysis implies that the conformation moves according to the collective modes when the peptide is in the initial stage of protein unfolding and in the final stage of protein folding.

  11. General-Relativistic Three-Dimensional Multi-group Neutrino Radiation-Hydrodynamics Simulations of Core-Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Roberts, Luke F.; Ott, Christian D.; Haas, Roland; O'Connor, Evan P.; Diener, Peter; Schnetter, Erik

    2016-11-01

    We report on a set of long-term general-relativistic three-dimensional (3D) multi-group (energy-dependent) neutrino radiation-hydrodynamics simulations of core-collapse supernovae. We employ a full 3D two-moment scheme with the local M1 closure, three neutrino species, and 12 energy groups per species. With this, we follow the post-core-bounce evolution of the core of a nonrotating 27 - {M}⊙ progenitor in full unconstrained 3D and in octant symmetry for ≳380 ms. We find the development of an asymmetric runaway explosion in our unconstrained simulation. We test the resolution dependence of our results and, in agreement with previous work, find that low resolution artificially aids explosion and leads to an earlier runaway expansion of the shock. At low resolution, the octant and full 3D dynamics are qualitatively very similar, but at high resolution, only the full 3D simulation exhibits the onset of explosion.

  12. Simulating the effects of the 1991 Mount Pinatubo volcanic eruption using the ARPEGE atmosphere general circulation model

    NASA Astrophysics Data System (ADS)

    Otterå, Odd Helge

    2008-03-01

    The climate changes that occured following the volcanic eruption of Mount Pinatubo in the Phillippines on 15 June 1991 have been simulated using the ARPEGE atmosphere general circulation model (AGCM). The model was forced by a reconstructed spatial-time distribution of stratospheric aerosols intended for use in long climate simulations. Four statistical ensembles of the AGCM simulations with and without volcanic aerosols over a period of 5 years following the eruption have been made, and the calculated fields have been compared to available observations. The model is able to reproduce some of the observed features after the eruption, such as the winter warming pattern that was observed over the Northern Hemisphere (NH) during the following winters. This pattern was caused by an enhanced Equator-to-pole temperature gradient in the stratosphere that developed due to aerosol heating of the tropics. This in turn led to a strengthening of the polar vortex, which tends to modulate the planetary wave field in such a way that an anomalously positive Arctic Oscillation pattern is produced in the troposphere and at the surface, favouring warm conditions over the NH. During the summer, the model produced a more uniform cooling over the NH.

  13. Examining the accuracy of astrophysical disk simulations with a generalized hydrodynamical test problem [The role of pressure and viscosity in SPH simulations of astrophysical disks

    SciTech Connect

    Raskin, Cody; Owen, J. Michael

    2016-10-24

    Here, we discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extension of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.

  14. Examining the accuracy of astrophysical disk simulations with a generalized hydrodynamical test problem [The role of pressure and viscosity in SPH simulations of astrophysical disks

    DOE PAGES

    Raskin, Cody; Owen, J. Michael

    2016-10-24

    Here, we discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extensionmore » of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.« less

  15. Simulations of driven overdamped frictionless hard spheres

    NASA Astrophysics Data System (ADS)

    Lerner, Edan; Düring, Gustavo; Wyart, Matthieu

    2013-03-01

    We introduce an event-driven simulation scheme for overdamped dynamics of frictionless hard spheres subjected to external forces, neglecting hydrodynamic interactions. Our event-driven approach is based on an exact equation of motion which relates the driving force to the resulting velocities through the geometric information characterizing the underlying network of contacts between the hard spheres. Our method allows for a robust extraction of the instantaneous coordination of the particles as well as contact force statistics and dynamics, under any chosen driving force, in addition to shear flow and compression. It can also be used for generating high-precision jammed packings under shear, compression, or both. We present a number of additional applications of our method.

  16. Radiative, two-temperature simulations of low-luminosity black hole accretion flows in general relativity

    NASA Astrophysics Data System (ADS)

    Sądowski, Aleksander; Wielgus, Maciek; Narayan, Ramesh; Abarca, David; McKinney, Jonathan C.; Chael, Andrew

    2017-04-01

    We present a numerical method that evolves a two-temperature, magnetized, radiative, accretion flow around a black hole, within the framework of general relativistic radiation magnetohydrodynamics. As implemented in the code KORAL, the gas consists of two sub-components - ions and electrons - which share the same dynamics but experience independent, relativistically consistent, thermodynamical evolution. The electrons and ions are heated independently according to a prescription from the literature for magnetohydrodynamical turbulent dissipation. Energy exchange between the particle species via Coulomb collisions is included. In addition, electrons gain and lose energy and momentum by absorbing and emitting synchrotron and bremsstrahlung radiation and through Compton scattering. All evolution equations are handled within a fully covariant framework in the relativistic fixed-metric space-time of the black hole. Numerical results are presented for five models of low-luminosity black hole accretion. In the case of a model with a mass accretion rate dot{M}˜ 4× 10^{-8} dot{M}_Edd, we find that radiation has a negligible effect on either the dynamics or the thermodynamics of the accreting gas. In contrast, a model with a larger dot{M}˜ 4× 10^{-4} dot{M}_Edd behaves very differently. The accreting gas is much cooler and the flow is geometrically less thick, though it is not quite a thin accretion disc.

  17. Simulating the universe(s) II: phenomenology of cosmic bubble collisions in full general relativity

    NASA Astrophysics Data System (ADS)

    Wainwright, Carroll L.; Johnson, Matthew C.; Aguirre, Anthony; Peiris, Hiranya V.

    2014-10-01

    Observing the relics of collisions between bubble universes would provide direct evidence for the existence of an eternally inflating Multiverse; the non-observation of such events can also provide important constraints on inflationary physics. Realizing these prospects requires quantitative predictions for observables from the properties of the possible scalar field Lagrangians underlying eternal inflation. Building on previous work, we establish this connection in detail. We perform a fully relativistic numerical study of the phenomenology of bubble collisions in models with a single scalar field, computing the comoving curvature perturbation produced in a wide variety of models. We also construct a set of analytic predictions, allowing us to identify the phenomenologically relevant properties of the scalar field Lagrangian. The agreement between the analytic predictions and numerics in the relevant regions is excellent, and allows us to generalize our results beyond the models we adopt for the numerical studies. Specifically, the signature is completely determined by the spatial profile of the colliding bubble just before the collision, and the de Sitter invariant distance between the bubble centers. The analytic and numerical results support a power-law fit with an index 1< κ lesssim 2. For collisions between identical bubbles, we establish a lower-bound on the observed amplitude of collisions that is set by the present energy density in curvature.

  18. A NURBS-based generalized finite element scheme for 3D simulation of heterogeneous materials

    NASA Astrophysics Data System (ADS)

    Safdari, Masoud; Najafi, Ahmad R.; Sottos, Nancy R.; Geubelle, Philippe H.

    2016-08-01

    A 3D NURBS-based interface-enriched generalized finite element method (NIGFEM) is introduced to solve problems with complex discontinuous gradient fields observed in the analysis of heterogeneous materials. The method utilizes simple structured meshes of hexahedral elements that do not necessarily conform to the material interfaces in heterogeneous materials. By avoiding the creation of conforming meshes used in conventional FEM, the NIGFEM leads to significant simplification of the mesh generation process. To achieve an accurate solution in elements that are crossed by material interfaces, the NIGFEM utilizes Non-Uniform Rational B-Splines (NURBS) to enrich the solution field locally. The accuracy and convergence of the NIGFEM are tested by solving a benchmark problem. We observe that the NIGFEM preserves an optimal rate of convergence, and provides additional advantages including the accurate capture of the solution fields in the vicinity of material interfaces and the built-in capability for hierarchical mesh refinement. Finally, the use of the NIGFEM in the computational analysis of heterogeneous materials is discussed.

  19. El Nino-southern oscillation simulated in an MRI atmosphere-ocean coupled general circulation model

    SciTech Connect

    Nagai, T.; Tokioka, T.; Endoh, M.; Kitamura, Y. )

    1992-11-01

    A coupled atmosphere-ocean general circulation model (GCM) was time integrated for 30 years to study interannual variability in the tropics. The atmospheric component is a global GCM with 5 levels in the vertical and 4[degrees]latitude X 5[degrees] longitude grids in the horizontal including standard physical processes (e.g., interactive clouds). The oceanic component is a GCM for the Pacific with 19 levels in the vertical and 1[degrees]x 2.5[degrees] grids in the horizontal including seasonal varying solar radiation as forcing. The model succeeded in reproducing interannual variations that resemble the El Nino-Southern Oscillation (ENSO) with realistic seasonal variations in the atmospheric and oceanic fields. The model ENSO cycle has a time scale of approximately 5 years and the model El Nino (warm) events are locked roughly in phase to the seasonal cycle. The cold events, however, are less evident in comparison with the El Nino events. The time scale of the model ENSO cycle is determined by propagation time of signals from the central-eastern Pacific to the western Pacific and back to the eastern Pacific. Seasonal timing is also important in the ENSO time scale: wind anomalies in the central-eastern Pacific occur in summer and the atmosphere ocean coupling in the western Pacific operates efficiently in the first half of the year.

  20. Merger of white dwarf-neutron star binaries: Prelude to hydrodynamic simulations in general relativity

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; MacLeod, Morgan; Baumgarte, Thomas W.; Shapiro, Stuart L.

    2010-02-01

    White dwarf-neutron star binaries generate detectable gravitational radiation. We construct Newtonian equilibrium models of corotational white dwarf-neutron star (WDNS) binaries in circular orbit and find that these models terminate at the Roche limit. At this point the binary will undergo either stable mass transfer (SMT) and evolve on a secular time scale, or unstable mass transfer (UMT), which results in the tidal disruption of the WD. The path a given binary will follow depends primarily on its mass ratio. We analyze the fate of known WDNS binaries and use population synthesis results to estimate the number of LISA-resolved galactic binaries that will undergo either SMT or UMT. We model the quasistationary SMT epoch by solving a set of simple ordinary differential equations and compute the corresponding gravitational waveforms. Finally, we discuss in general terms the possible fate of binaries that undergo UMT. If sufficient WD debris lands on the NS, the remnant may collapse, whereby the gravitational waves from the inspiral, merger, and collapse phases will sweep from LISA through LIGO frequency bands. If the debris forms a disk about the NS, it may fragment and form planets. )

  1. Simulating the universe(s) II: phenomenology of cosmic bubble collisions in full general relativity

    SciTech Connect

    Wainwright, Carroll L.; Aguirre, Anthony; Johnson, Matthew C.; Peiris, Hiranya V. E-mail: mjohnson@perimeterinstitute.ca E-mail: h.peiris@ucl.ac.uk

    2014-10-01

    Observing the relics of collisions between bubble universes would provide direct evidence for the existence of an eternally inflating Multiverse; the non-observation of such events can also provide important constraints on inflationary physics. Realizing these prospects requires quantitative predictions for observables from the properties of the possible scalar field Lagrangians underlying eternal inflation. Building on previous work, we establish this connection in detail. We perform a fully relativistic numerical study of the phenomenology of bubble collisions in models with a single scalar field, computing the comoving curvature perturbation produced in a wide variety of models. We also construct a set of analytic predictions, allowing us to identify the phenomenologically relevant properties of the scalar field Lagrangian. The agreement between the analytic predictions and numerics in the relevant regions is excellent, and allows us to generalize our results beyond the models we adopt for the numerical studies. Specifically, the signature is completely determined by the spatial profile of the colliding bubble just before the collision, and the de Sitter invariant distance between the bubble centers. The analytic and numerical results support a power-law fit with an index 1< κ ∼< 2. For collisions between identical bubbles, we establish a lower-bound on the observed amplitude of collisions that is set by the present energy density in curvature.

  2. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    NASA Astrophysics Data System (ADS)

    Jöckel, P.; Tost, H.; Pozzer, A.; Brühl, C.; Buchholz, J.; Ganzeveld, L.; Hoor, P.; Kerkweg, A.; Lawrence, M. G.; Sander, R.; Steil, B.; Stiller, G.; Tanarhte, M.; Taraborrelli, D.; van Aardenne, J.; Lelieveld, J.

    2006-07-01

    The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model version up to 0.01 hPa was used at T42 resolution (~2.8 latitude and longitude) to simulate the lower and middle atmosphere. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. A Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998-2005. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce the Quasi-Biennial Oscillation and major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated accurately, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of interannual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request.

  3. Comparisons of spectral thermospheric general circulation model simulations and E and F region chemical release wind observations

    NASA Astrophysics Data System (ADS)

    Mikkelsen, I. S.; Larsen, M. F.

    1993-03-01

    High-latitude chemical release wind measurements were carried out in February and March 1978, in March 1985, and in March 1987. In each of the experiments, wind profiles were obtained covering heights in both the E and the F region. Three of the release experiments were carried out on the evening side of the auroral oval and one on the morning side. Two sets of measurements were carried out in disturbed conditions at solar maximum, while the other two were carried out during quiet periods at solar minimum. The spectral thermospheric general circulation model that has been developed at the Danish Meteorological Institute is used to simulate the conditions appropriate to each of the four experiments and detailed comparisons between the model predictions and the measurements are presented. Considering the uncertainties in the various external sources of forcing, such as the plasma convection patterns, the model adequately reproduces the major features of all the wind profiles. However in the E region the relative wind maxima from the model are, in general, above the heights of the observed wind maxima, possibly due to the oversimplified auroral precipitation used in the model, with the electrons being represented by single Maxwellian energy spectra only. The uncoupled neutral and ionized atmospheric compositions used in the model may also explain part of the unrealistic simulated winds. The upward propagating tides are found to modify the E region winds significantly, even under disturbed conditions when the plasma forcing might be expected to dominate the dynamics. In our results the latter is shown by the sensitivity of the simulated flows to the lower boundary condition which is the imposed tidal oscillation structure.

  4. Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

    NASA Technical Reports Server (NTRS)

    Pankine, A. A.; Ingersoll, Andrew P.

    2002-01-01

    We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

  5. Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

    NASA Technical Reports Server (NTRS)

    Pankine, A. A.; Ingersoll, Andrew P.

    2002-01-01

    We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

  6. Winter polar warmings and the meridional transport on Mars simulated with a general circulation model

    NASA Astrophysics Data System (ADS)

    Medvedev, Alexander S.; Hartogh, Paul

    2007-01-01

    Winter polar warmings in the middle atmosphere of Mars occur due to the adiabatic heating associated with the downward branch of the cross-equatorial meridional circulation. Thus, they are the manifestation of the global meridional transport rather than of local radiative effects. We report on a series of numerical experiments with a recently developed general circulation model of the martian atmosphere to examine the relative roles of the mechanical and thermal forcing in the meridional transport. The experiments were focused on answering the question of whether the martian circulation is consistent with the thermally driven nearly inviscid Hadley cell, as was pointed out by some previous studies, or it is forced mainly by zonally asymmetric eddies. It is demonstrated that, under realistic conditions in the middle atmosphere, the meridional transport is maintained primarily by dissipating large-scale planetary waves and solar tides. This mechanism is similar to the "extratropical pump" in the middle atmosphere on Earth. Only in the run with artificially weak zonal disturbances, was the circulation reminiscent of thermally induced Hadley cells. In the experiment with an imposed dust storm, the modified atmospheric refraction changes the vertical propagation of the eddies. As the result, the Eliassen-Palm fluxes convergence increases in high winter latitudes of the middle atmosphere, the meridional transport gets stronger, and the polar temperature rises. Additional numerical experiments demonstrated that insufficient model resolution, increased numerical dissipation, and, especially, neglect of non-LTE effects for the 15 μm CO 2 band could weaken the meridional transport and the magnitude of polar warmings in GCMs.

  7. A simulation study of confounding in generalized linear models for air pollution epidemiology.

    PubMed Central

    Chen, C; Chock, D P; Winkler, S L

    1999-01-01

    Confounding between the model covariates and causal variables (which may or may not be included as model covariates) is a well-known problem in regression models used in air pollution epidemiology. This problem is usually acknowledged but hardly ever investigated, especially in the context of generalized linear models. Using synthetic data sets, the present study shows how model overfit, underfit, and misfit in the presence of correlated causal variables in a Poisson regression model affect the estimated coefficients of the covariates and their confidence levels. The study also shows how this effect changes with the ranges of the covariates and the sample size. There is qualitative agreement between these study results and the corresponding expressions in the large-sample limit for the ordinary linear models. Confounding of covariates in an overfitted model (with covariates encompassing more than just the causal variables) does not bias the estimated coefficients but reduces their significance. The effect of model underfit (with some causal variables excluded as covariates) or misfit (with covariates encompassing only noncausal variables), on the other hand, leads to not only erroneous estimated coefficients, but a misguided confidence, represented by large t-values, that the estimated coefficients are significant. The results of this study indicate that models which use only one or two air quality variables, such as particulate matter [less than and equal to] 10 microm and sulfur dioxide, are probably unreliable, and that models containing several correlated and toxic or potentially toxic air quality variables should also be investigated in order to minimize the situation of model underfit or misfit. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:10064552

  8. Outflow Channels and Martian Climate: General Circulation Model (GCM) Simulations with Emplaced Water and Cloud Physics

    NASA Astrophysics Data System (ADS)

    Santiago, D.; Colaprete, A.; Haberle, R.; Asphaug, E.; Sloan, L.

    2005-12-01

    One of the most intriguing signatures of surface water on Mars is large outflow channels believed to have been carved out by gigantic flood events in the late Noachian or Hesperian. We use the NASA Ames Mars General Circulation Model (MGCM) to study how abrupt eruption of water onto the Martian surface might have affected the early climate of Mars, and to calculate where the water ultimately went as part of a transient hydrologic cycle. Our model includes the emplacement of large amounts of water onto the surface of a cold, dry Mars in the vicinity of Ares Valles, with current day orbital configurations. Specifically, 106 km3 of water was released at a rate of 0.1 km3/s at end of Northern Hemisphere summer. We have begun modeling with the MGCM with outflow water and cloud physics. The current cloud physics include cloud particle nucleation and growth, with radiative effects added at a later date. These results are being compared with a control case with no outflow in the model, and a case with water, but without clouds. In all cases we are examining the radiative effects of water vapor, albedo effects of water ice, and latent heat effects for this large influx of water. Preliminary results show differences between these three cases, but the factors that are causing these differences have not yet been determined. These results will be interesting to compare with studies that suggest significant, but possibly localized or regional, precipitation in the Hesperian, as opposed to the more widely recognized precipitation during the Noachian. Current analyses and longer model runs will allow us to calculate the specific effects of outflow water on past Martian climate, as well as where the water might have ended up.

  9. Outflow Channels and Martian Climate: General Circulation Model (GCM) Simulations with Emplaced Water

    NASA Astrophysics Data System (ADS)

    Santiago, D.; Colaprete, A.; Haberle, R.; Asphaug, E.; Sloan, L.

    2005-08-01

    The existence of past surface water on Mars has been inferred on the basis of geomorphologic interpretation of spacecraft images. Among the most intriguing signatures of surface water are large outflow channels believed to have been carved out by gigantic flood events in the late Noachian or Hesperian. We use the NASA Ames Mars General Circulation Model (MGCM) to study how abrupt eruption of water onto the Martian surface might have affected climate, and to consider where the water ultimately went. Our initial model begins by emplacing large amounts of water onto the surface of Mars in the vicinity of Ares Valley, for current day orbital configurations. Specifically, 10\\^6 km\\^3 of water was released at a rate of 0.1 km\\^3/s at end of Northern summer. The MGCM was run for 10 years; a control version, without water, was run the same length of time, in order to assess the climatic impact from the radiative and thermal effects of the released water. Model modifications for the results that will be presented include (1) a customized sublimation scheme, (2) latent heat effects of water transitions, (3) radiative effects of water vapor, (4) albedo effects, and (5) clouds. Preliminary results indicate slight surface temperature increases due to latent heating is areas of water deposition, and cooling in the outflow formation area. Results also suggest that water vapor is distributed throughout the atmosphere. Results for these and other atmospheric variables, as well as water tracer distribution, will be presented. We acknowledge the University Aligned Research Center and the Mars Fundamental Research Program for their funding contributions.

  10. Numerical simulation of 137Cs and (239,240)Pu concentrations by an ocean general circulation model.

    PubMed

    Tsumune, Daisuke; Aoyama, Michio; Hirose, Katsumi

    2003-01-01

    We simulated the spatial distributions and the temporal variations of 137Cs and (239,240)Pu concentrations in the ocean by using the ocean general circulation model which was developed by National Center of Atmospheric Research. These nuclides are introduced into seawaters from global fallout due to atmospheric nuclear weapons tests. The distribution of radioactive deposition on the world ocean is estimated from global precipitation data and observed values of annual deposition of radionuclides at the Meteorological Research Institute in Japan and several observed points in New Zealand. Radionuclides from global fallout have been transported by advection, diffusion and scavenging, and this concentration reduces by radioactive decay in the ocean. We verified the results of the model calculations by comparing simulated values of 137Cs and (239,240)Pu in seawater with the observed values included in the Historical Artificial Radionuclides in the HAM database, which has been constructed by the Meteorological Research Institute. The vertical distributions of the calculated 137Cs concentrations were in good agreement and are in good agreement with the observed profiles in the 1960s up to 250 m, in the 1970s up to 500 m, in the 1980s up to 750 m and in the 1990s up to 750 m. However, the calculated 137Cs concentrations were underestimated compared with the observed 137Cs at the deeper layer. This may suggest other transport processes of 137Cs to deep waters. The horizontal distributions of 137Cs concentrations in surface water could be simulated. A numerical tracer release experiment was performed to explain the horizontal distribution pattern. A maximum (239,240)Pu concentration layer occurs at an intermediate depth for both observed and calculated values, which is formed by particle scavenging. The horizontal distributions of the calculated (239,240)Pu concentrations in surface water could be simulated by considering the scavenging effect.

  11. Nested generalized linear mixed model with ordinal response: Simulation and application on poverty data in Java Island

    NASA Astrophysics Data System (ADS)

    Widyaningsih, Yekti; Saefuddin, Asep; Notodiputro, Khairil A.; Wigena, Aji H.

    2012-05-01

    The objective of this research is to build a nested generalized linear mixed model using an ordinal response variable with some covariates. There are three main jobs in this paper, i.e. parameters estimation procedure, simulation, and implementation of the model for the real data. At the part of parameters estimation procedure, concepts of threshold, nested random effect, and computational algorithm are described. The simulations data are built for 3 conditions to know the effect of different parameter values of random effect distributions. The last job is the implementation of the model for the data about poverty in 9 districts of Java Island. The districts are Kuningan, Karawang, and Majalengka chose randomly in West Java; Temanggung, Boyolali, and Cilacap from Central Java; and Blitar, Ngawi, and Jember from East Java. The covariates in this model are province, number of bad nutrition cases, number of farmer families, and number of health personnel. In this modeling, all covariates are grouped as ordinal scale. Unit observation in this research is sub-district (kecamatan) nested in district, and districts (kabupaten) are nested in province. For the result of simulation, ARB (Absolute Relative Bias) and RRMSE (Relative Root of mean square errors) scale is used. They show that prov parameters have the highest bias, but more stable RRMSE in all conditions. The simulation design needs to be improved by adding other condition, such as higher correlation between covariates. Furthermore, as the result of the model implementation for the data, only number of farmer family and number of medical personnel have significant contributions to the level of poverty in Central Java and East Java province, and only district 2 (Karawang) of province 1 (West Java) has different random effect from the others. The source of the data is PODES (Potensi Desa) 2008 from BPS (Badan Pusat Statistik).

  12. Simulation of the Small-Scale Dust Activities and Their Mutual Interactions on the Atmospheric Dynamics Using a High-Resolution Mars General Circulation Model

    NASA Astrophysics Data System (ADS)

    Kuroda, T.; Kadowaki, M.

    2017-06-01

    We show the simulation results of our high-resolution Mars general circulation model including the dust lifting processes for the investigations of the meteorological features which invoke dust storms and subsequent enhancement of small-scale waves.

  13. Network-based simulation of aircraft at gates in airport terminals

    SciTech Connect

    Cheng, Y.

    1998-03-01

    Simulation is becoming an essential tool for planning, design, and management of airport facilities. A simulation of aircraft at gates at an airport can be applied for various periodically performed applications, relating to the dynamic behavior of aircraft at gates in airport terminals for analyses, evaluations, and decision supports. Conventionally, such simulations are implemented using an event-driven method. For a more efficient simulation, this paper proposes a network-based method. The basic idea is to transform all the sequence constraint relations of aircraft at gates into a network. The simulation is done by calculating the longest path to all the nodes in the network. The effect of the algorithm of the proposed method has been examined by experiments, and the superiority of the proposed method over the event-driven method is revealed through comprehensive comparisons of their overall simulation performance.

  14. Work Practice Simulation of Complex Human-Automation Systems in Safety Critical Situations: The Brahms Generalized berlingen Model

    NASA Technical Reports Server (NTRS)

    Clancey, William J.; Linde, Charlotte; Seah, Chin; Shafto, Michael

    2013-01-01

    The transition from the current air traffic system to the next generation air traffic system will require the introduction of new automated systems, including transferring some functions from air traffic controllers to on­-board automation. This report describes a new design verification and validation (V&V) methodology for assessing aviation safety. The approach involves a detailed computer simulation of work practices that includes people interacting with flight-critical systems. The research is part of an effort to develop new modeling and verification methodologies that can assess the safety of flight-critical systems, system configurations, and operational concepts. The 2002 Ueberlingen mid-air collision was chosen for analysis and modeling because one of the main causes of the accident was one crew's response to a conflict between the instructions of the air traffic controller and the instructions of TCAS, an automated Traffic Alert and Collision Avoidance System on-board warning system. It thus furnishes an example of the problem of authority versus autonomy. It provides a starting point for exploring authority/autonomy conflict in the larger system of organization, tools, and practices in which the participants' moment-by-moment actions take place. We have developed a general air traffic system model (not a specific simulation of Überlingen events), called the Brahms Generalized Ueberlingen Model (Brahms-GUeM). Brahms is a multi-agent simulation system that models people, tools, facilities/vehicles, and geography to simulate the current air transportation system as a collection of distributed, interactive subsystems (e.g., airports, air-traffic control towers and personnel, aircraft, automated flight systems and air-traffic tools, instruments, crew). Brahms-GUeM can be configured in different ways, called scenarios, such that anomalous events that contributed to the Überlingen accident can be modeled as functioning according to requirements or in an

  15. How to Hold a Model Legislature: A Simulation of the Georgia General Assembly, Teacher's Manual [And] The Model Legislature, Student's Kit.

    ERIC Educational Resources Information Center

    Jackson, Edwin L.

    The student's kit and teacher's manual provide a framework for secondary students to simulate the functionings of Georgia's General Assembly. Objectives of the simulation are to help students: (1) experience the forces and conflicts involved in lawmaking, (2) learn about the role of legislators, (3) understand and discuss issues facing citizens,…

  16. How to Hold a Model Legislature: A Simulation of the Georgia General Assembly, Teacher's Manual [And] The Model Legislature, Student's Kit.

    ERIC Educational Resources Information Center

    Jackson, Edwin L.

    The student's kit and teacher's manual provide a framework for secondary students to simulate the functionings of Georgia's General Assembly. Objectives of the simulation are to help students: (1) experience the forces and conflicts involved in lawmaking, (2) learn about the role of legislators, (3) understand and discuss issues facing citizens,…

  17. Calculation of 3-D free electron laser gain: Comparison with simulation and generalization to elliptical cross section

    SciTech Connect

    Chin, Yong Ho; Kim, Kwang-Je; Xie, Ming.

    1992-08-01

    In the previous paper, we have derived a dispersion relation for the free electron laser (FEL) gain in the exponential regime taking account the diffraction and electron's betatron oscillation. Here, we compare the growth rates obtained by solving the dispersion relation with those obtained by simulation calculation for the waterbag and the Gaussian models for the electron's transverse phase space distribution. The agreement is found to be good except for the limiting case where the Rayleigh length is much longer than the gain length (1-D limit). We also generalize the analysis to the case where the electron beam cross section is elliptical as is usually the case in storage rings, and derive the first-order dispersion relation.

  18. Calculation of 3-D free electron laser gain: Comparison with simulation and generalization to elliptical cross section

    SciTech Connect

    Chin, Yong Ho; Kim, Kwang-Je; Xie, Ming

    1992-08-01

    In the previous paper, we have derived a dispersion relation for the free electron laser (FEL) gain in the exponential regime taking account the diffraction and electron`s betatron oscillation. Here, we compare the growth rates obtained by solving the dispersion relation with those obtained by simulation calculation for the waterbag and the Gaussian models for the electron`s transverse phase space distribution. The agreement is found to be good except for the limiting case where the Rayleigh length is much longer than the gain length (1-D limit). We also generalize the analysis to the case where the electron beam cross section is elliptical as is usually the case in storage rings, and derive the first-order dispersion relation.

  19. EARTHQUAKE RESPONSE ANALYSIS OF STEEL PORTAL FRAMES BY PSEUDODYNAMIC SIMULATION TECHNIQUE USING A GENERAL-PURPOSE FINITE ELEMENT ANALYSIS PROGRAM

    NASA Astrophysics Data System (ADS)

    Miki, Toshihiro; Mizusawa, Tomisaku; Yamada, Osamu; Toda, Tomoki

    This paper studies the earthquake response of steel portal frames when the shear collapse occurs at the centre of the beam. The pseudodynamic simulation technique for the earthquake response analysis of the frames is developed in correspondence to the pseudodynamic substructure testing method. For the thin-walled box element under shear force in the middle of beam, the numerical process is utilized by a general-purpose finite element analysis program. The numerical results show the shear collapse behaviour in stiffened box beams and corresponding restoring force - displacement relationship of frames. The advantages of shear collapse of beams for the use in frames during earthquakes are discussed from the point of view of the hysteretic energy dissipated by the column base.

  20. Use of Generalized Fluid System Simulation Program (GFSSP) for Teaching and Performing Senior Design Projects at the Educational Institutions

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.; Hedayat, A.

    2015-01-01

    Thi