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Sample records for hoko simulation model

  1. Aviation Safety Simulation Model

    NASA Technical Reports Server (NTRS)

    Houser, Scott; Yackovetsky, Robert (Technical Monitor)

    2001-01-01

    The Aviation Safety Simulation Model is a software tool that enables users to configure a terrain, a flight path, and an aircraft and simulate the aircraft's flight along the path. The simulation monitors the aircraft's proximity to terrain obstructions, and reports when the aircraft violates accepted minimum distances from an obstruction. This model design facilitates future enhancements to address other flight safety issues, particularly air and runway traffic scenarios. This report shows the user how to build a simulation scenario and run it. It also explains the model's output.

  2. Computer Modeling and Simulation

    SciTech Connect

    Pronskikh, V. S.

    2014-05-09

    Verification and validation of computer codes and models used in simulation are two aspects of the scientific practice of high importance and have recently been discussed by philosophers of science. While verification is predominantly associated with the correctness of the way a model is represented by a computer code or algorithm, validation more often refers to model’s relation to the real world and its intended use. It has been argued that because complex simulations are generally not transparent to a practitioner, the Duhem problem can arise for verification and validation due to their entanglement; such an entanglement makes it impossible to distinguish whether a coding error or model’s general inadequacy to its target should be blamed in the case of the model failure. I argue that in order to disentangle verification and validation, a clear distinction between computer modeling (construction of mathematical computer models of elementary processes) and simulation (construction of models of composite objects and processes by means of numerical experimenting with them) needs to be made. Holding on to that distinction, I propose to relate verification (based on theoretical strategies such as inferences) to modeling and validation, which shares the common epistemology with experimentation, to simulation. To explain reasons of their intermittent entanglement I propose a weberian ideal-typical model of modeling and simulation as roles in practice. I suggest an approach to alleviate the Duhem problem for verification and validation generally applicable in practice and based on differences in epistemic strategies and scopes

  3. Theory Modeling and Simulation

    SciTech Connect

    Shlachter, Jack

    2012-08-23

    Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.

  4. SSPX simulation model

    SciTech Connect

    Fowler, T K

    1999-09-20

    An analytical approximation to an R-L-C circuit representing SSPX is shown to reproduce the observed capacitor bank efficiency and gun optimization data. As in the SPICE code, the spheromak gun is represented by a fixed resistance chosen to balance energy transfer to the gun. A revised estimate of the magnetic decay time in SSPX Shot 1822 then brings our estimate of the gun efficiency itself in line with the observed spheromak magnetic field for this shot. Prompted by these successes, we present a turbulence-based theoretical model for the spheromak resistance that can be implemented in the SPICE code, of the form: R{sub s} = {kappa}I (1-I{sub 0}/I){sup 2} where I is the gun current, I{sub 0} = ({Lambda}{sub 0}/{mu}{sub 0}){Phi} with bias flux and Taylor eigenvalue {lambda}{sub 0}, and {kappa} is a coefficient based on the magnetic turbulence model employed in Dan Hua's spheromak simulation code. The value of {kappa} giving a good energy balance (around 0.1 m{Omega}/KA) implies substantial turbulence levels. Implementing our model in SPICE would provide a calibration for theoretical calculations of the turbulence. Our analytic approximation to the SPICE code provides guidance to optimize future performance in SSPX, the greatest benefit appearing to come from reducing or eliminating the protective resistor to increase bank efficiency. Eliminating the resistor altogether doubles the bank efficiency and the spheromak magnetic energy.

  5. Automatic programming of simulation models

    NASA Technical Reports Server (NTRS)

    Schroer, Bernard J.; Tseng, Fan T.; Zhang, Shou X.; Dwan, Wen S.

    1988-01-01

    The objective of automatic programming is to improve the overall environment for describing the program. This improved environment is realized by a reduction in the amount of detail that the programmer needs to know and is exposed to. Furthermore, this improved environment is achieved by a specification language that is more natural to the user's problem domain and to the user's way of thinking and looking at the problem. The goal of this research is to apply the concepts of automatic programming (AP) to modeling discrete event simulation system. Specific emphasis is on the design and development of simulation tools to assist the modeler define or construct a model of the system and to then automatically write the corresponding simulation code in the target simulation language, GPSS/PC. A related goal is to evaluate the feasibility of various languages for constructing automatic programming simulation tools.

  6. Simulation modeling of estuarine ecosystems

    NASA Technical Reports Server (NTRS)

    Johnson, R. W.

    1980-01-01

    A simulation model has been developed of Galveston Bay, Texas ecosystem. Secondary productivity measured by harvestable species (such as shrimp and fish) is evaluated in terms of man-related and controllable factors, such as quantity and quality of inlet fresh-water and pollutants. This simulation model used information from an existing physical parameters model as well as pertinent biological measurements obtained by conventional sampling techniques. Predicted results from the model compared favorably with those from comparable investigations. In addition, this paper will discuss remotely sensed and conventional measurements in the framework of prospective models that may be used to study estuarine processes and ecosystem productivity.

  7. TREAT Modeling and Simulation Strategy

    SciTech Connect

    DeHart, Mark David

    2015-09-01

    This report summarizes a four-phase process used to describe the strategy in developing modeling and simulation software for the Transient Reactor Test Facility. The four phases of this research and development task are identified as (1) full core transient calculations with feedback, (2) experiment modeling, (3) full core plus experiment simulation and (4) quality assurance. The document describes the four phases, the relationship between these research phases, and anticipated needs within each phase.

  8. Modeling and Simulation at NASA

    NASA Technical Reports Server (NTRS)

    Steele, Martin J.

    2009-01-01

    This slide presentation is composed of two topics. The first reviews the use of modeling and simulation (M&S) particularly as it relates to the Constellation program and discrete event simulation (DES). DES is defined as a process and system analysis, through time-based and resource constrained probabilistic simulation models, that provide insight into operation system performance. The DES shows that the cycles for a launch from manufacturing and assembly to launch and recovery is about 45 days and that approximately 4 launches per year are practicable. The second topic reviews a NASA Standard for Modeling and Simulation. The Columbia Accident Investigation Board made some recommendations related to models and simulations. Some of the ideas inherent in the new standard are the documentation of M&S activities, an assessment of the credibility, and reporting to decision makers, which should include the analysis of the results, a statement as to the uncertainty in the results,and the credibility of the results. There is also discussion about verification and validation (V&V) of models. There is also discussion about the different types of models and simulation.

  9. Advanced Space Shuttle simulation model

    NASA Technical Reports Server (NTRS)

    Tatom, F. B.; Smith, S. R.

    1982-01-01

    A non-recursive model (based on von Karman spectra) for atmospheric turbulence along the flight path of the shuttle orbiter was developed. It provides for simulation of instantaneous vertical and horizontal gusts at the vehicle center-of-gravity, and also for simulation of instantaneous gusts gradients. Based on this model the time series for both gusts and gust gradients were generated and stored on a series of magnetic tapes, entitled Shuttle Simulation Turbulence Tapes (SSTT). The time series are designed to represent atmospheric turbulence from ground level to an altitude of 120,000 meters. A description of the turbulence generation procedure is provided. The results of validating the simulated turbulence are described. Conclusions and recommendations are presented. One-dimensional von Karman spectra are tabulated, while a discussion of the minimum frequency simulated is provided. The results of spectral and statistical analyses of the SSTT are presented.

  10. Fuzzy modeling and simulation

    NASA Astrophysics Data System (ADS)

    Pedrycz, Witold

    1993-12-01

    The paradigm of fuzzy modelling entails development of relationships (dependencies) between the linguistic entities defined for system's variables. The key feature of the fuzzy models pertains to their significant flexibility so they could easily be modified to comply with the principle of incompatibility. Considering the existing panoply of fuzzy models one can easily conclude that most of them are embraced under an umbrella of a single conceptual structure. From a functional point of view this structure is perceived as a combination of the two conceptual interfaces and a single processing block aimed at developing calculus of the linguistic labels. The interfaces produce all the links that are necessary to combine the physical (numerical) level of the real-world system with that of a conceptual character realized within the fuzzy model and articulated at the level of the linguistic entities. The presentation will address the main methodological aspects concerning these functional components with a particular emphasis placed on the associated design principles. The main issues dominating the design of the interfaces pertain to the implemented level of information granularity, optimality of linguistic labels, and linguistic-to-numerical transformations. The processing level of the fuzzy modelling will be considered through the use of fuzzy neural networks. These distributed computing structures are highly heterogeneous as they are constructed with the aid of several distinct types of logic-oriented neurons. The advantages of the fuzzy neural networks such as an implicit scheme of knowledge encapsulation that is carried out there will be discussed in detail.

  11. Simulation of a model microswimmer

    NASA Astrophysics Data System (ADS)

    Downton, Matthew T.; Stark, Holger

    2009-05-01

    We discuss the modelling of a microswimmer that operates in a 'squirmer' mode, by means of stochastic rotation dynamics. The squirmer that we model can easily be tuned between a 'pusher' and a 'puller'. We examine the flows produced by the squirmer and find that there is good agreement between both the predicted and simulated velocities of locomotion and the resulting flow field.

  12. Simulation of a model microswimmer.

    PubMed

    Downton, Matthew T; Stark, Holger

    2009-05-20

    We discuss the modelling of a microswimmer that operates in a 'squirmer' mode, by means of stochastic rotation dynamics. The squirmer that we model can easily be tuned between a 'pusher' and a 'puller'. We examine the flows produced by the squirmer and find that there is good agreement between both the predicted and simulated velocities of locomotion and the resulting flow field.

  13. Stochastic models: theory and simulation.

    SciTech Connect

    Field, Richard V., Jr.

    2008-03-01

    Many problems in applied science and engineering involve physical phenomena that behave randomly in time and/or space. Examples are diverse and include turbulent flow over an aircraft wing, Earth climatology, material microstructure, and the financial markets. Mathematical models for these random phenomena are referred to as stochastic processes and/or random fields, and Monte Carlo simulation is the only general-purpose tool for solving problems of this type. The use of Monte Carlo simulation requires methods and algorithms to generate samples of the appropriate stochastic model; these samples then become inputs and/or boundary conditions to established deterministic simulation codes. While numerous algorithms and tools currently exist to generate samples of simple random variables and vectors, no cohesive simulation tool yet exists for generating samples of stochastic processes and/or random fields. There are two objectives of this report. First, we provide some theoretical background on stochastic processes and random fields that can be used to model phenomena that are random in space and/or time. Second, we provide simple algorithms that can be used to generate independent samples of general stochastic models. The theory and simulation of random variables and vectors is also reviewed for completeness.

  14. Automatic programming of simulation models

    NASA Technical Reports Server (NTRS)

    Schroer, Bernard J.; Tseng, Fan T.; Zhang, Shou X.; Dwan, Wen S.

    1990-01-01

    The concepts of software engineering were used to improve the simulation modeling environment. Emphasis was placed on the application of an element of rapid prototyping, or automatic programming, to assist the modeler define the problem specification. Then, once the problem specification has been defined, an automatic code generator is used to write the simulation code. The following two domains were selected for evaluating the concepts of software engineering for discrete event simulation: manufacturing domain and a spacecraft countdown network sequence. The specific tasks were to: (1) define the software requirements for a graphical user interface to the Automatic Manufacturing Programming System (AMPS) system; (2) develop a graphical user interface for AMPS; and (3) compare the AMPS graphical interface with the AMPS interactive user interface.

  15. Modeling and Simulation for Safeguards

    SciTech Connect

    Swinhoe, Martyn T.

    2012-07-26

    The purpose of this talk is to give an overview of the role of modeling and simulation in Safeguards R&D and introduce you to (some of) the tools used. Some definitions are: (1) Modeling - the representation, often mathematical, of a process, concept, or operation of a system, often implemented by a computer program; (2) Simulation - the representation of the behavior or characteristics of one system through the use of another system, especially a computer program designed for the purpose; and (3) Safeguards - the timely detection of diversion of significant quantities of nuclear material. The role of modeling and simulation are: (1) Calculate amounts of material (plant modeling); (2) Calculate signatures of nuclear material etc. (source terms); and (3) Detector performance (radiation transport and detection). Plant modeling software (e.g. FACSIM) gives the flows and amount of material stored at all parts of the process. In safeguards this allow us to calculate the expected uncertainty of the mass and evaluate the expected MUF. We can determine the measurement accuracy required to achieve a certain performance.

  16. Multiscale Stochastic Simulation and Modeling

    SciTech Connect

    James Glimm; Xiaolin Li

    2006-01-10

    Acceleration driven instabilities of fluid mixing layers include the classical cases of Rayleigh-Taylor instability, driven by a steady acceleration and Richtmyer-Meshkov instability, driven by an impulsive acceleration. Our program starts with high resolution methods of numerical simulation of two (or more) distinct fluids, continues with analytic analysis of these solutions, and the derivation of averaged equations. A striking achievement has been the systematic agreement we obtained between simulation and experiment by using a high resolution numerical method and improved physical modeling, with surface tension. Our study is accompanies by analysis using stochastic modeling and averaged equations for the multiphase problem. We have quantified the error and uncertainty using statistical modeling methods.

  17. Animal models for simulating weightlessness

    NASA Technical Reports Server (NTRS)

    Morey-Holton, E.; Wronski, T. J.

    1982-01-01

    NASA has developed a rat model to simulate on earth some aspects of the weightlessness alterations experienced in space, i.e., unloading and fluid shifts. Comparison of data collected from space flight and from the head-down rat suspension model suggests that this model system reproduces many of the physiological alterations induced by space flight. Data from various versions of the rat model are virtually identical for the same parameters; thus, modifications of the model for acute, chronic, or metabolic studies do not alter the results as long as the critical components of the model are maintained, i.e., a cephalad shift of fluids and/or unloading of the rear limbs.

  18. Assessment of Molecular Modeling & Simulation

    SciTech Connect

    2002-01-03

    This report reviews the development and applications of molecular and materials modeling in Europe and Japan in comparison to those in the United States. Topics covered include computational quantum chemistry, molecular simulations by molecular dynamics and Monte Carlo methods, mesoscale modeling of material domains, molecular-structure/macroscale property correlations like QSARs and QSPRs, and related information technologies like informatics and special-purpose molecular-modeling computers. The panel's findings include the following: The United States leads this field in many scientific areas. However, Canada has particular strengths in DFT methods and homogeneous catalysis; Europe in heterogeneous catalysis, mesoscale, and materials modeling; and Japan in materials modeling and special-purpose computing. Major government-industry initiatives are underway in Europe and Japan, notably in multi-scale materials modeling and in development of chemistry-capable ab-initio molecular dynamics codes.

  19. Simulation Framework for Teaching in Modeling and Simulation Areas

    ERIC Educational Resources Information Center

    De Giusti, Marisa Raquel; Lira, Ariel Jorge; Villarreal, Gonzalo Lujan

    2008-01-01

    Simulation is the process of executing a model that describes a system with enough detail; this model has its entities, an internal state, some input and output variables and a list of processes bound to these variables. Teaching a simulation language such as general purpose simulation system (GPSS) is always a challenge, because of the way it…

  20. Standard for Models and Simulations

    NASA Technical Reports Server (NTRS)

    Steele, Martin J.

    2016-01-01

    This NASA Technical Standard establishes uniform practices in modeling and simulation to ensure essential requirements are applied to the design, development, and use of models and simulations (MS), while ensuring acceptance criteria are defined by the program project and approved by the responsible Technical Authority. It also provides an approved set of requirements, recommendations, and criteria with which MS may be developed, accepted, and used in support of NASA activities. As the MS disciplines employed and application areas involved are broad, the common aspects of MS across all NASA activities are addressed. The discipline-specific details of a given MS should be obtained from relevant recommended practices. The primary purpose is to reduce the risks associated with MS-influenced decisions by ensuring the complete communication of the credibility of MS results.

  1. Simulating spin models on GPU

    NASA Astrophysics Data System (ADS)

    Weigel, Martin

    2011-09-01

    Over the last couple of years it has been realized that the vast computational power of graphics processing units (GPUs) could be harvested for purposes other than the video game industry. This power, which at least nominally exceeds that of current CPUs by large factors, results from the relative simplicity of the GPU architectures as compared to CPUs, combined with a large number of parallel processing units on a single chip. To benefit from this setup for general computing purposes, the problems at hand need to be prepared in a way to profit from the inherent parallelism and hierarchical structure of memory accesses. In this contribution I discuss the performance potential for simulating spin models, such as the Ising model, on GPU as compared to conventional simulations on CPU.

  2. Rule-based simulation models

    NASA Technical Reports Server (NTRS)

    Nieten, Joseph L.; Seraphine, Kathleen M.

    1991-01-01

    Procedural modeling systems, rule based modeling systems, and a method for converting a procedural model to a rule based model are described. Simulation models are used to represent real time engineering systems. A real time system can be represented by a set of equations or functions connected so that they perform in the same manner as the actual system. Most modeling system languages are based on FORTRAN or some other procedural language. Therefore, they must be enhanced with a reaction capability. Rule based systems are reactive by definition. Once the engineering system has been decomposed into a set of calculations using only basic algebraic unary operations, a knowledge network of calculations and functions can be constructed. The knowledge network required by a rule based system can be generated by a knowledge acquisition tool or a source level compiler. The compiler would take an existing model source file, a syntax template, and a symbol table and generate the knowledge network. Thus, existing procedural models can be translated and executed by a rule based system. Neural models can be provide the high capacity data manipulation required by the most complex real time models.

  3. Creating Simulated Microgravity Patient Models

    NASA Technical Reports Server (NTRS)

    Hurst, Victor; Doerr, Harold K.; Bacal, Kira

    2004-01-01

    The Medical Operational Support Team (MOST) has been tasked by the Space and Life Sciences Directorate (SLSD) at the NASA Johnson Space Center (JSC) to integrate medical simulation into 1) medical training for ground and flight crews and into 2) evaluations of medical procedures and equipment for the International Space Station (ISS). To do this, the MOST requires patient models that represent the physiological changes observed during spaceflight. Despite the presence of physiological data collected during spaceflight, there is no defined set of parameters that illustrate or mimic a 'space normal' patient. Methods: The MOST culled space-relevant medical literature and data from clinical studies performed in microgravity environments. The areas of focus for data collection were in the fields of cardiovascular, respiratory and renal physiology. Results: The MOST developed evidence-based patient models that mimic the physiology believed to be induced by human exposure to a microgravity environment. These models have been integrated into space-relevant scenarios using a human patient simulator and ISS medical resources. Discussion: Despite the lack of a set of physiological parameters representing 'space normal,' the MOST developed space-relevant patient models that mimic microgravity-induced changes in terrestrial physiology. These models are used in clinical scenarios that will medically train flight surgeons, biomedical flight controllers (biomedical engineers; BME) and, eventually, astronaut-crew medical officers (CMO).

  4. Verifying and Validating Simulation Models

    SciTech Connect

    Hemez, Francois M.

    2015-02-23

    This presentation is a high-level discussion of the Verification and Validation (V&V) of computational models. Definitions of V&V are given to emphasize that “validation” is never performed in a vacuum; it accounts, instead, for the current state-of-knowledge in the discipline considered. In particular comparisons between physical measurements and numerical predictions should account for their respective sources of uncertainty. The differences between error (bias), aleatoric uncertainty (randomness) and epistemic uncertainty (ignorance, lack-of- knowledge) are briefly discussed. Four types of uncertainty in physics and engineering are discussed: 1) experimental variability, 2) variability and randomness, 3) numerical uncertainty and 4) model-form uncertainty. Statistical sampling methods are available to propagate, and analyze, variability and randomness. Numerical uncertainty originates from the truncation error introduced by the discretization of partial differential equations in time and space. Model-form uncertainty is introduced by assumptions often formulated to render a complex problem more tractable and amenable to modeling and simulation. The discussion concludes with high-level guidance to assess the “credibility” of numerical simulations, which stems from the level of rigor with which these various sources of uncertainty are assessed and quantified.

  5. Simulated annealing model of acupuncture

    NASA Astrophysics Data System (ADS)

    Shang, Charles; Szu, Harold

    2015-05-01

    The growth control singularity model suggests that acupuncture points (acupoints) originate from organizers in embryogenesis. Organizers are singular points in growth control. Acupuncture can cause perturbation of a system with effects similar to simulated annealing. In clinical trial, the goal of a treatment is to relieve certain disorder which corresponds to reaching certain local optimum in simulated annealing. The self-organizing effect of the system is limited and related to the person's general health and age. Perturbation at acupoints can lead a stronger local excitation (analogous to higher annealing temperature) compared to perturbation at non-singular points (placebo control points). Such difference diminishes as the number of perturbed points increases due to the wider distribution of the limited self-organizing activity. This model explains the following facts from systematic reviews of acupuncture trials: 1. Properly chosen single acupoint treatment for certain disorder can lead to highly repeatable efficacy above placebo 2. When multiple acupoints are used, the result can be highly repeatable if the patients are relatively healthy and young but are usually mixed if the patients are old, frail and have multiple disorders at the same time as the number of local optima or comorbidities increases. 3. As number of acupoints used increases, the efficacy difference between sham and real acupuncture often diminishes. It predicted that the efficacy of acupuncture is negatively correlated to the disease chronicity, severity and patient's age. This is the first biological - physical model of acupuncture which can predict and guide clinical acupuncture research.

  6. Uterine Contraction Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Liu, Miao; Belfore, Lee A.; Shen, Yuzhong; Scerbo, Mark W.

    2010-01-01

    Building a training system for medical personnel to properly interpret fetal heart rate tracing requires developing accurate models that can relate various signal patterns to certain pathologies. In addition to modeling the fetal heart rate signal itself, the change of uterine pressure that bears strong relation to fetal heart rate and provides indications of maternal and fetal status should also be considered. In this work, we have developed a group of parametric models to simulate uterine contractions during labor and delivery. Through analysis of real patient records, we propose to model uterine contraction signals by three major components: regular contractions, impulsive noise caused by fetal movements, and low amplitude noise invoked by maternal breathing and measuring apparatus. The regular contractions are modeled by an asymmetric generalized Gaussian function and least squares estimation is used to compute the parameter values of the asymmetric generalized Gaussian function based on uterine contractions of real patients. Regular contractions are detected based on thresholding and derivative analysis of uterine contractions. Impulsive noise caused by fetal movements and low amplitude noise by maternal breathing and measuring apparatus are modeled by rational polynomial functions and Perlin noise, respectively. Experiment results show the synthesized uterine contractions can mimic the real uterine contractions realistically, demonstrating the effectiveness of the proposed algorithm.

  7. Operations planning simulation: Model study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The use of simulation modeling for the identification of system sensitivities to internal and external forces and variables is discussed. The technique provides a means of exploring alternate system procedures and processes, so that these alternatives may be considered on a mutually comparative basis permitting the selection of a mode or modes of operation which have potential advantages to the system user and the operator. These advantages are measurements is system efficiency are: (1) the ability to meet specific schedules for operations, mission or mission readiness requirements or performance standards and (2) to accomplish the objectives within cost effective limits.

  8. Impulse pumping modelling and simulation

    NASA Astrophysics Data System (ADS)

    Pierre, B.; Gudmundsson, J. S.

    2010-08-01

    Impulse pumping is a new pumping method based on propagation of pressure waves. Of particular interest is the application of impulse pumping to artificial lift situations, where fluid is transported from wellbore to wellhead using pressure waves generated at wellhead. The motor driven element of an impulse pumping apparatus is therefore located at wellhead and can be separated from the flowline. Thus operation and maintenance of an impulse pump are facilitated. The paper describes the different elements of an impulse pumping apparatus, reviews the physical principles and details the modelling of the novel pumping method. Results from numerical simulations of propagation of pressure waves in water-filled pipelines are then presented for illustrating impulse pumping physical principles, and validating the described modelling with experimental data.

  9. A modular BLSS simulation model

    NASA Technical Reports Server (NTRS)

    Rummel, John D.; Volk, Tyler

    1987-01-01

    A bioregenerative life support system (BLSS) for extraterrestrial use will be faced with coordination problems more acute than those in any ecosystem found on Earth. A related problem in BLSS design is providing an interface between the various life support processors, one that will allow for their coordination while still allowing for system expansion. A modular model is presented of a BLSS that interfaces system processors only with the material storage reservoirs, allowing those reservoirs to act as the principal buffers in the system and thus minimizing difficulties with processor coordination. The modular nature of the model allows independent development of the detailed submodels that exist within the model framework. Using this model, BLSS dynamics were investigated under normal conditions and under various failure modes. Partial and complete failures of various components, such as the waste processors or the plants themselves, drive transient responses in the model system, allowing the examination of the effectiveness of the system reservoirs as buffers. The results from simulations help to determine control strategies and BLSS design requirements. An evolved version could be used as an interactive control aid in a future BLSS.

  10. Ubiquitin: molecular modeling and simulations.

    PubMed

    Ganoth, Assaf; Tsfadia, Yossi; Wiener, Reuven

    2013-11-01

    The synthesis and destruction of proteins are imperative for maintaining their cellular homeostasis. In the 1970s, Aaron Ciechanover, Avram Hershko, and Irwin Rose discovered that certain proteins are tagged by ubiquitin before degradation, a discovery that awarded them the 2004 Nobel Prize in Chemistry. Compelling data gathered during the last several decades show that ubiquitin plays a vital role not only in protein degradation but also in many cellular functions including DNA repair processes, cell cycle regulation, cell growth, immune system functionality, hormone-mediated signaling in plants, vesicular trafficking pathways, regulation of histone modification and viral budding. Due to the involvement of ubiquitin in such a large number of diverse cellular processes, flaws and impairments in the ubiquitin system were found to be linked to cancer, neurodegenerative diseases, genetic disorders, and immunological disorders. Hence, deciphering the dynamics and complexity of the ubiquitin system is of significant importance. In addition to experimental techniques, computational methodologies have been gaining increasing influence in protein research and are used to uncover the structure, stability, folding, mechanism of action and interactions of proteins. Notably, molecular modeling and molecular dynamics simulations have become powerful tools that bridge the gap between structure and function while providing dynamic insights and illustrating essential mechanistic characteristics. In this study, we present an overview of molecular modeling and simulations of ubiquitin and the ubiquitin system, evaluate the status of the field, and offer our perspective on future progress in this area of research.

  11. Modeling of Army Research Laboratory EMP simulators

    SciTech Connect

    Miletta, J.R.; Chase, R.J.; Luu, B.B. ); Williams, J.W.; Viverito, V.J. )

    1993-12-01

    Models are required that permit the estimation of emitted field signatures from EMP simulators to design the simulator antenna structure, to establish the usable test volumes, and to estimate human exposure risk. This paper presents the capabilities and limitations of a variety of EMP simulator models useful to the Army's EMP survivability programs. Comparisons among frequency and time-domain models are provided for two powerful US Army Research Laboratory EMP simulators: AESOP (Army EMP Simulator Operations) and VEMPS II (Vertical EMP Simulator II).

  12. Aeroacoustic simulation for phonation modeling

    NASA Astrophysics Data System (ADS)

    Irwin, Jeffrey; Hanford, Amanda; Craven, Brent; Krane, Michael

    2011-11-01

    The phonation process occurs as air expelled from the lungs creates a pressure drop and a subsequent air flow across the larynx. The fluid-structure interaction between the turbulent air flow and oscillating vocal folds, combined with additional resonance in the oral and nasal cavities, creates much of what we hear in the human voice. As many voice-related disorders can be traced to irregular vocal tract shape or motion, it is important to understand in detail the physics involved in the phonation process. To numerically compute the physics of phonation, a solver must be able to accurately model acoustic airflow through a moving domain. The open-source CFD package OpenFOAM is currently being used to evaluate existing solvers against simple acoustic test cases, including an open-ended resonator and an expansion chamber, both of which utilize boundary conditions simulating acoustic sources as well as anechoic termination. Results of these test cases will be presented and compared with theory, and the future development of a three-dimensional vocal tract model and custom-mode acoustic solver will be discussed. Acknowledge support of NIH grant 5R01DC005642 and ARL E&F program.

  13. Benchmark simulation models, quo vadis?

    PubMed

    Jeppsson, U; Alex, J; Batstone, D J; Benedetti, L; Comas, J; Copp, J B; Corominas, L; Flores-Alsina, X; Gernaey, K V; Nopens, I; Pons, M-N; Rodríguez-Roda, I; Rosen, C; Steyer, J-P; Vanrolleghem, P A; Volcke, E I P; Vrecko, D

    2013-01-01

    As the work of the IWA Task Group on Benchmarking of Control Strategies for wastewater treatment plants (WWTPs) is coming to an end, it is essential to disseminate the knowledge gained. For this reason, all authors of the IWA Scientific and Technical Report on benchmarking have come together to provide their insights, highlighting areas where knowledge may still be deficient and where new opportunities are emerging, and to propose potential avenues for future development and application of the general benchmarking framework and its associated tools. The paper focuses on the topics of temporal and spatial extension, process modifications within the WWTP, the realism of models, control strategy extensions and the potential for new evaluation tools within the existing benchmark system. We find that there are major opportunities for application within all of these areas, either from existing work already being done within the context of the benchmarking simulation models (BSMs) or applicable work in the wider literature. Of key importance is increasing capability, usability and transparency of the BSM package while avoiding unnecessary complexity.

  14. Structured building model reduction toward parallel simulation

    SciTech Connect

    Dobbs, Justin R.; Hencey, Brondon M.

    2013-08-26

    Building energy model reduction exchanges accuracy for improved simulation speed by reducing the number of dynamical equations. Parallel computing aims to improve simulation times without loss of accuracy but is poorly utilized by contemporary simulators and is inherently limited by inter-processor communication. This paper bridges these disparate techniques to implement efficient parallel building thermal simulation. We begin with a survey of three structured reduction approaches that compares their performance to a leading unstructured method. We then use structured model reduction to find thermal clusters in the building energy model and allocate processing resources. Experimental results demonstrate faster simulation and low error without any interprocessor communication.

  15. An introduction to enterprise modeling and simulation

    SciTech Connect

    Ostic, J.K.; Cannon, C.E.

    1996-09-01

    As part of an ongoing effort to continuously improve productivity, quality, and efficiency of both industry and Department of Energy enterprises, Los Alamos National Laboratory is investigating various manufacturing and business enterprise simulation methods. A number of enterprise simulation software models are being developed to enable engineering analysis of enterprise activities. In this document the authors define the scope of enterprise modeling and simulation efforts, and review recent work in enterprise simulation at Los Alamos National Laboratory as well as at other industrial, academic, and research institutions. References of enterprise modeling and simulation methods and a glossary of enterprise-related terms are provided.

  16. Yankee Rowe simulator core model validation

    SciTech Connect

    Napolitano, M.E.

    1990-01-01

    This paper presents the validation of the Yankee Rowe simulator core model. Link-Miles Simulation Corporation is developing the Yankee Rowe simulator and Yankee Atomic Electric Company is involved in input and benchmark data generation, as well as simulator validation. Core model validation by Yankee comprises three tasks: (1) careful generation of fuel reactivity characteristics (B constants); (2) nonintegrated core model testing; and (3) fully integrated core model testing. Simulator core model validation and verification is a multistage process involving input and benchmark data generation as well as interactive debugging. Core characteristics were brought within acceptable criteria by this process. This process was achieved through constant communication between Link-Miles and Yankee engineers. Based on this validation, the Yankee Rowe simulator core model is found to be acceptable for training purposes.

  17. Juno model rheometry and simulation

    NASA Astrophysics Data System (ADS)

    Sampl, Manfred; Macher, Wolfgang; Oswald, Thomas; Plettemeier, Dirk; Rucker, Helmut O.; Kurth, William S.

    2016-10-01

    The experiment Waves aboard the Juno spacecraft, which will arrive at its target planet Jupiter in 2016, was devised to study the plasma and radio waves of the Jovian magnetosphere. We analyzed the Waves antennas, which consist of two nonparallel monopoles operated as a dipole. For this investigation we applied two independent methods: the experimental technique, rheometry, which is based on a downscaled model of the spacecraft to measure the antenna properties in an electrolytic tank and numerical simulations, based on commercial computer codes, from which the quantities of interest (antenna impedances and effective length vectors) are calculated. In this article we focus on the results for the low-frequency range up to about 4 MHz, where the antenna system is in the quasi-static regime. Our findings show that there is a significant deviation of the effective length vectors from the physical monopole directions, caused by the presence of the conducting spacecraft body. The effective axes of the antenna monopoles are offset from the mechanical axes by more than 30°, and effective lengths show a reduction to about 60% of the antenna rod lengths. The antennas' mutual capacitances are small compared to the self-capacitances, and the latter are almost the same for the two monopoles. The overall performance of the antennas in dipole configuration is very stable throughout the frequency range up to about 4-5 MHz and therefore can be regarded as the upper frequency bound below which the presented quasi-static results are applicable.

  18. Theory, Modeling, and Simulation of Semiconductor Lasers

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Saini, Subbash (Technical Monitor)

    1998-01-01

    Semiconductor lasers play very important roles in many areas of information technology. In this talk, I will first give an overview of semiconductor laser theory. This will be followed by a description of different models and their shortcomings in modeling and simulation. Our recent efforts in constructing a fully space and time resolved simulation model will then be described. Simulation results based on our model will be presented. Finally the effort towards a self-consistent and comprehensive simulation capability for the opto-electronics integrated circuits (OEICs) will be briefly reviewed.

  19. Evaluating uncertainty in stochastic simulation models

    SciTech Connect

    McKay, M.D.

    1998-02-01

    This paper discusses fundamental concepts of uncertainty analysis relevant to both stochastic simulation models and deterministic models. A stochastic simulation model, called a simulation model, is a stochastic mathematical model that incorporates random numbers in the calculation of the model prediction. Queuing models are familiar simulation models in which random numbers are used for sampling interarrival and service times. Another example of simulation models is found in probabilistic risk assessments where atmospheric dispersion submodels are used to calculate movement of material. For these models, randomness comes not from the sampling of times but from the sampling of weather conditions, which are described by a frequency distribution of atmospheric variables like wind speed and direction as a function of height above ground. A common characteristic of simulation models is that single predictions, based on one interarrival time or one weather condition, for example, are not nearly as informative as the probability distribution of possible predictions induced by sampling the simulation variables like time and weather condition. The language of model analysis is often general and vague, with terms having mostly intuitive meaning. The definition and motivations for some of the commonly used terms and phrases offered in this paper lead to an analysis procedure based on prediction variance. In the following mathematical abstraction the authors present a setting for model analysis, relate practical objectives to mathematical terms, and show how two reasonable premises lead to a viable analysis strategy.

  20. Interactive simulation of needle insertion models.

    PubMed

    DiMaio, Simon P; Salcudean, Septimiu E

    2005-07-01

    A novel interactive virtual needle insertion simulation is presented. The simulation models are based on measured planar tissue deformations and needle insertion forces. Since the force-displacement relationship is only of interest along the needle shaft, a condensation technique is shown to reduce the computational complexity of linear simulation models significantly. As the needle penetrates or is withdrawn from the tissue model, the boundary conditions that determine the tissue and needle motion change. Boundary condition and local material coordinate changes are facilitated by fast low-rank matrix updates. A large-strain elastic needle model is coupled to the tissue models to account for needle deflection and bending during simulated insertion. A haptic environment, based on these novel interactive simulation techniques, allows users to manipulate a three-degree-of-freedom virtual needle as it penetrates virtual tissue models, while experiencing steering torques and lateral needle forces through a planar haptic interface.

  1. VHDL simulation with access to transistor models

    NASA Technical Reports Server (NTRS)

    Gibson, J.

    1991-01-01

    Hardware description languages such as VHDL have evolved to aid in the design of systems with large numbers of elements and a wide range of electronic and logical abstractions. For high performance circuits, behavioral models may not be able to efficiently include enough detail to give designers confidence in a simulation's accuracy. One option is to provide a link between the VHDL environment and a transistor level simulation environment. The coupling of the Vantage Analysis Systems VHDL simulator and the NOVA simulator provides the combination of VHDL modeling and transistor modeling.

  2. SSA Modeling and Simulation with DIRSIG

    NASA Astrophysics Data System (ADS)

    Bennett, D.; Allen, D.; Dank, J.; Gartley, M.; Tyler, D.

    2014-09-01

    We describe and demonstrate a robust, physics-based modeling system to simulate ground and space-based observations of both LEO and GEO objects. With the DIRSIG radiometry engine at its core, our system exploits STK, adaptive optics modeling, and detector effects to produce high fidelity simulated images and radiometry. Key to generating quantitative simulations is our ability to attribute engineering-quality, faceted CAD models with reflective and emissive properties derived from laboratory measurements, including the spatial structure of such difficult materials as MLI. In addition to simulated video imagery, we will demonstrate a computational procedure implementing a position-based dynamics approach to shrink wrap MLI around space components.

  3. Resist profile simulation with fast lithography model

    NASA Astrophysics Data System (ADS)

    He, Yan-Ying; Chou, Chih-Shiang; Tang, Yu-Po; Huang, Wen-Chun; Liu, Ru-Gun; Gau, Tsai-Sheng

    2014-03-01

    A traditional approach to construct a fast lithographic model is to match wafer top-down SEM images, contours and/or gauge CDs with a TCC model plus some simple resist representation. This modeling method has been proven and is extensively used for OPC modeling. As the technology moves forward, this traditional approach has become insufficient in regard to lithography weak point detection, etching bias prediction, etc. The drawback of this approach is from metrology and simulation. First, top-down SEM is only good for acquiring planar CD information. Some 3D metrology such as cross-section SEM or AFM is necessary to obtain the true resist profile. Second, the TCC modeling approach is only suitable for planar image simulation. In order to model the resist profile, full 3D image simulation is needed. Even though there are many rigorous simulators capable of catching the resist profile very well, none of them is feasible for full-chip application due to the tremendous consumption of computational resource. The authors have proposed a quasi-3D image simulation method in the previous study [1], which is suitable for full-chip simulation with the consideration of sidewall angles, to improve the model accuracy of planar models. In this paper, the quasi-3D image simulation is extended to directly model the resist profile with AFM and/or cross-section SEM data. Resist weak points detected by the model generated with this 3D approach are verified on the wafer.

  4. An integrated data model for reservoir simulation

    SciTech Connect

    Aydelotte, S.R.

    1994-02-01

    This paper describes the capability of the Epicenter data model to manage reservoir-simulation information, including the spatial model used to describe the properties of the earth and the product-flow network mode used to describe production performance. In addition to data values, the data model describes data creation and quality and provides a reliable means of understanding the source. To use the data model, reservoir-simulation applications need to be rewritten to conform to the data-model nomenclature and conventions. While this is a significant task, the benefit to reservoir simulation practitioners and vendors includes integration of technical applications (such as mapping, well logging, and geophysical interpretation systems), data portability (allowing Vendor A's simulator to use data prepared by Vendor B's preprocessor), and interpretability such as using a third-party optimization package to conduct a series of simulations.

  5. Interactive communication systems simulation model - ICSSM

    NASA Astrophysics Data System (ADS)

    Wade, W. D.; Mortara, M. E.; Leong, P. K.; Frost, V. S.

    1984-01-01

    The design of ICSSM, a nonreal time computer-aided simulation and analysis tool for communications systems, is presented, ICSSM is capable of supporting modeling, simulation, and analysis of any system representable in terms of a network of multiport functional blocks. Its applicability is limited only by the modeler's ingenuity to decompose the system to functional blocks and to represent these functional blocks algorithmically. ICSSM has been constructed modularly, consisting of five subsytems to facilitate the tasks of formulating the model, exercising the model, evaluating and showing the simulation results, and storing and maintaining a library of modeling elements, analysis, and utility subroutines. It is written exclusively in ANSI Standard Fortran IV language, and is now operational in a Honeywell DPS 7/80 M computer under the MULTICS Operating System. Description of a recent simulation using ICSSM and some generic modules of general interest developed as a result of the modeling work are also presented.

  6. CAUSA - An Environment For Modeling And Simulation

    NASA Astrophysics Data System (ADS)

    Dilger, Werner; Moeller, Juergen

    1989-03-01

    CAUSA is an environment for modeling and simulation of dynamic systems on a quantitative level. The environment provides a conceptual framework including primitives like objects, processes and causal dependencies which allow the modeling of a broad class of complex systems. The facility of simulation allows the quantitative and qualitative inspection and empirical investigation of the behavior of the modeled system. CAUSA is implemented in Knowledge-Craft and runs on a Symbolics 3640.

  7. Simulations of the Domain State Model

    DTIC Science & Technology

    2003-01-01

    bulk of the antiferromagnet, the latter is diluted throughout its volume. Extensive Monte Carlo simulations of the model were performed in the past...that a corresponding theoretical model, the domain state model, investigated by Monte Carlo simulations shows a behavior very similar to the...discuss this in detail in the following. 15 RESULTS Monte Carlo methods are used with a heat-bath algorithm and single-spin flip dynamics [26] for the

  8. GIS Enabled Modeling and Simulation (GEMS)

    DTIC Science & Technology

    2007-06-01

    polygons, visual databases include texture information to provide a visualization of ground and material types. These databases include 3D models ...US Army TEC GIS-Enabled Modeling and Simulation project, and was the lead developer on the building interior semantic information portion of the...GIS Enabled Modeling and Simulation (GEMS) Thomas Stanzione Kevin Johnson MAK Technologies 68 Moulton Street Cambridge, MA 02138 (617) 876

  9. SIMULATION MODELING OF GASTROINTESTINAL ABSORPTION

    EPA Science Inventory

    Mathematical dosimetry models incorporate mechanistic determinants of chemical disposition in a living organism to describe relationships between exposure concentration and the internal dose needed for PBPK models and human health risk assessment. Because they rely on determini...

  10. Intelligent Mobility Modeling and Simulation

    DTIC Science & Technology

    2015-03-04

    templates • Motion: Vehicle mobility, arm models, wheel/soil dynamics – slippage/sinkage • Hardware models: Kinematics, dynamics, motors, encoders, IMU ...Approved for public release. #26550 UMich (ARC) Autonomy Algorithm Overview LIDAR Data Processing LIDAR Vehicle state sensors: GPS, IMU , etc. Define...displays Sensor Data Parameters Camera model IMU / GPS models Sensor Processing Delays A u to n o m y Si m u la ti o n For use if autonomous

  11. An Extensible Reduced Order Model Builder for Simulation and Modeling

    SciTech Connect

    2012-09-28

    REVEAL is a software framework for building reduced order models (surrogate models) for high fidelity complex scientific simulations. REVEAL is designed to do reduced order modeling and sensitivity analysis for scientific simulations. REVEAL incorporates a range of sampling and regression methods. It provides complete user environment and is adaptable to new simulators, runs jobs on any computing platform of choice, automatically post processes simulation results and provides a range of data analysis tools. The software is generic and can easily be extended to incorporate new methods, simulators.

  12. Electric Vehicle Modeling and Simulation.

    DTIC Science & Technology

    1983-08-01

    simulation were used to select a viable *electric vehicle system to compete economically with conventional USAF passenger cars . This system was then...It is, however, also used by the Environment Pro- tection Agency for new car urban fuel economy tests. This 23-minute cycle is the recorded...batteries that could be conveniently installed within the body of the car while retaining four passenger capa- bility was twelve. Based on the

  13. Computer modeling and simulation of human movement.

    PubMed

    Pandy, M G

    2001-01-01

    Recent interest in using modeling and simulation to study movement is driven by the belief that this approach can provide insight into how the nervous system and muscles interact to produce coordinated motion of the body parts. With the computational resources available today, large-scale models of the body can be used to produce realistic simulations of movement that are an order of magnitude more complex than those produced just 10 years ago. This chapter reviews how the structure of the neuromusculoskeletal system is commonly represented in a multijoint model of movement, how modeling may be combined with optimization theory to simulate the dynamics of a motor task, and how model output can be analyzed to describe and explain muscle function. Some results obtained from simulations of jumping, pedaling, and walking are also reviewed to illustrate the approach.

  14. Software-Engineering Process Simulation (SEPS) model

    NASA Technical Reports Server (NTRS)

    Lin, C. Y.; Abdel-Hamid, T.; Sherif, J. S.

    1992-01-01

    The Software Engineering Process Simulation (SEPS) model is described which was developed at JPL. SEPS is a dynamic simulation model of the software project development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life cycle development activities and management decision making processes. The model is designed to be a planning tool to examine tradeoffs of cost, schedule, and functionality, and to test the implications of different managerial policies on a project's outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmodern assessments.

  15. Simulation modeling and analysis with Arena

    SciTech Connect

    Tayfur Altiok; Benjamin Melamed

    2007-06-15

    The textbook which treats the essentials of the Monte Carlo discrete-event simulation methodology, and does so in the context of a popular Arena simulation environment. It treats simulation modeling as an in-vitro laboratory that facilitates the understanding of complex systems and experimentation with what-if scenarios in order to estimate their performance metrics. The book contains chapters on the simulation modeling methodology and the underpinnings of discrete-event systems, as well as the relevant underlying probability, statistics, stochastic processes, input analysis, model validation and output analysis. All simulation-related concepts are illustrated in numerous Arena examples, encompassing production lines, manufacturing and inventory systems, transportation systems, and computer information systems in networked settings. Chapter 13.3.3 is on coal loading operations on barges/tugboats.

  16. Scalable Online Network Modeling and Simulation

    DTIC Science & Technology

    2005-08-01

    ONLINE NETWORK MODELING AND SIMULATION 6. AUTHOR(S) Boleslaw Szymanski, Shivkumar Kalyanaraman, Biplab Sikdar and Christopher Carothers 5...PI of this project, Prof. Kenneth Vastola, replaced later by co-PI, Prof. Biplab Sikdar . With significant progress in silicon technologies, storage...Winter Simulation Conference (WSC 󈧈), December 2004. 3. K. Chandrayana, S. Ramakrishnan, B. Sikdar , S. Kalyanaraman, On randomizing the sending

  17. Rabi multi-sector reservoir simulation model

    SciTech Connect

    Bruijnzeels, C.; O`Halloran, C.

    1995-12-31

    To ensure optimum ultimate recovery of the 46 meter thick oil rim of the Rabi Field in Gabon, a full field simulation model was required. Due to it`s size and complexity, with local cusping, coning and geological circumstances dominating individual well behavior, a single full field model would be too large for existing hardware. A method was developed to simulate the full field with 5 separate sector models, whilst allowing the development in one sector model to have an effect on the boundary conditions of another sector. In this manner, the 13 x 4.5 km field could be simulated with a horizontal well spacing down to 175 meter. This paper focuses on the method used to attach single 3-phase tank cells to a sector simulation grid in order to represent non-simulated parts of the field. It also describes the history matching methodology and how to run a multisector model in forecasting mode. This method can be used for any reservoir, where size and complexity require large reservoir simulation models that normally could not be modeled within the constraints of available computer facilities. Detailed studies can be conducted on specific parts of a field, whilst allowing for dynamic flow and pressure effects caused by the rest of the field.

  18. Probabilistic-Based Modeling and Simulation Assessment

    DTIC Science & Technology

    2010-06-01

    mph crash simulation at 100 ms with an unbelted Hybrid III model The Hybrid III dummy model was then restrained using a finite element seatbelt ...true physics of the impact, and can thus be qualified as unwanted noise in the model response. Unfortunately, it is difficult to quantify the

  19. A Simulation To Model Exponential Growth.

    ERIC Educational Resources Information Center

    Appelbaum, Elizabeth Berman

    2000-01-01

    Describes a simulation using dice-tossing students in a population cluster to model the growth of cancer cells. This growth is recorded in a scatterplot and compared to an exponential function graph. (KHR)

  20. Triple Value Simulation Model Fact Sheet

    EPA Pesticide Factsheets

    The Triple Value Simulation (3VS) is a high-level model that accounts for the complex relationships among economic, social and environmental systems in order to explore scenarios and solutions to improve the health of the Bay.

  1. MNEQA, an emissions model for photochemical simulations

    NASA Astrophysics Data System (ADS)

    Ortega, S.; Soler, M. R.; Alarcón, M.; Arasa, R.

    This study focuses on a new emissions model, Numerical Emissions Model for Air Quality (MNEQA), to be used in photochemical simulations and emission control strategies relating to tropospheric ozone pollutants. MNEQA processes available local information from external files and is easily adaptable to any desired spatial resolution. Top-down and bottom-up methodologies are combined to calculate emissions at the required resolution for photochemical simulations. It was used in conjunction with the MM5-CMAQ air quality modelling system and was applied to an episode of high ozone levels in June 2003. Emission results are widely analysed showing a difference of -8.8% with EMEP NOx emissions, and -18.7% with EMEP VOC emissions. Related to ozone simulations, comparative results between measurements and simulations indicated good behaviour of the model in reproducing diurnal ozone concentrations, as statistical values fall within the EPA and EU regulatory frameworks.

  2. Mathematical Model Development and Simulation Support

    NASA Technical Reports Server (NTRS)

    Francis, Ronald C.; Tobbe, Patrick A.

    2000-01-01

    This report summarizes the work performed in support of the Contact Dynamics 6DOF Facility and the Flight Robotics Lab at NASA/ MSFC in the areas of Mathematical Model Development and Simulation Support.

  3. MODELING CONCEPTS FOR BMP/LID SIMULATION

    EPA Science Inventory

    Enhancement of simulation options for stormwater best management practices (BMPs) and hydrologic source control is discussed in the context of the EPA Storm Water Management Model (SWMM). Options for improvement of various BMP representations are presented, with emphasis on inco...

  4. Theory, modeling, and simulation annual report, 1992

    SciTech Connect

    Not Available

    1993-05-01

    This report briefly discusses research on the following topics: development of electronic structure methods; modeling molecular processes in clusters; modeling molecular processes in solution; modeling molecular processes in separations chemistry; modeling interfacial molecular processes; modeling molecular processes in the atmosphere; methods for periodic calculations on solids; chemistry and physics of minerals; graphical user interfaces for computational chemistry codes; visualization and analysis of molecular simulations; integrated computational chemistry environment; and benchmark computations.

  5. Segmented Mirror Telescope Model and Simulation

    DTIC Science & Technology

    2011-06-01

    NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS SEGMENTED MIRROR TELESCOPE MODEL AND SIMULATION by Travis W. Axtell June 2011 Thesis Co...Mirror Telescope Model and Simulation Travis W. Axtell Naval Postgraduate School Monterey, CA 93943 Department of the Navy Approved for public release...Department of Defense or the U.S. Government. IRB Protocol Number: N/A The Segmented Mirror Telescope (SMT) housed at the Naval Postgraduate School is a

  6. Defense Modeling and Simulation Initiative

    DTIC Science & Technology

    1992-05-01

    marketplace’s favor, such as the competition between the X-Windows Graphic User Interface frc -n Sun Computer (Open Look) and from the Open Systems... competition with incentives to superior producers? The third major issue is how to bring a powerful message concerning the benefits of interoperable M&S...algoriims, data structwres for real-time represenmion and modeling • Develop a global hierarchy ofinn erable environmental models - Develop inteligent

  7. Minimum-complexity helicopter simulation math model

    NASA Technical Reports Server (NTRS)

    Heffley, Robert K.; Mnich, Marc A.

    1988-01-01

    An example of a minimal complexity simulation helicopter math model is presented. Motivating factors are the computational delays, cost, and inflexibility of the very sophisticated math models now in common use. A helicopter model form is given which addresses each of these factors and provides better engineering understanding of the specific handling qualities features which are apparent to the simulator pilot. The technical approach begins with specification of features which are to be modeled, followed by a build up of individual vehicle components and definition of equations. Model matching and estimation procedures are given which enable the modeling of specific helicopters from basic data sources such as flight manuals. Checkout procedures are given which provide for total model validation. A number of possible model extensions and refinement are discussed. Math model computer programs are defined and listed.

  8. Multiscale model approach for magnetization dynamics simulations

    NASA Astrophysics Data System (ADS)

    De Lucia, Andrea; Krüger, Benjamin; Tretiakov, Oleg A.; Kläui, Mathias

    2016-11-01

    Simulations of magnetization dynamics in a multiscale environment enable the rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required. We have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales. To implement this, the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine. The software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization and use either a micromagnetic or an atomistic model. To demonstrate the validity of the multiscale approach, we simulate the spin wave transmission across the regions simulated with the two different models and different discretizations. We find that the interface between the regions is fully transparent for spin waves with frequency lower than a certain threshold set by the coarse scale micromagnetic model with no noticeable attenuation due to the interface between the models. As a comparison to exact analytical theory, we show that in a system with a Dzyaloshinskii-Moriya interaction leading to spin spirals, the simulated multiscale result is in good quantitative agreement with the analytical calculation.

  9. Trimming an aircraft model for flight simulation

    NASA Technical Reports Server (NTRS)

    Mcfarland, Richard E.

    1987-01-01

    Real-time piloted aircraft simulations with digital computers have been performed at Ames Research Center (ARC) for over two decades. For the simulation of conventional aircraft models, the establishment of initial vehicle and control orientations at various operational flight regimes has been adequately handled by either analog techniques or simple inversion processes. However, exotic helicopter configurations have been introduced recently that require more sophisticated techniques because of their expanded degrees of freedom and environmental vibration levels. At ARC, these techniques are used for the backward solutions to real-time simulation models as required for the generation of trim points. These techniques are presented in this paper with examples from a blade-element helicopter simulation model.

  10. MODEL FOR SIMULATING FLOODS IN RIVERS.

    USGS Publications Warehouse

    Schaffranek, Raymond W.

    1985-01-01

    A one-dimensional model capable of simulating flood wave propagation in a river or network of channels is presented. The computer model is programmed to provide maximum flexibility in the adaptation of channel geometry, the specification of conveyance properties, and the treatment of boundary conditions. An equation transformation procedure is employed in the model to minimize computer storage and execution time requirements by reducing the order of the resultant coefficient matrices. Based on a four-point implicit finite-difference approximation of the governing, nonlinear, flow equations, the model can be used to simulate the wide range of flow conditions typically encountered in various natural waterbody systems. Two particular applications are presented to demonstrate the computational features and capabilities of the model in the simulation of flood wave propagation.

  11. Architecting a Simulation Framework for Model Rehosting

    NASA Technical Reports Server (NTRS)

    Madden, Michael M.

    2004-01-01

    The utility of vehicle math models extends beyond human-in-the-loop simulation. It is desirable to deploy a given model across a multitude of applications that target design, analysis, and research. However, the vehicle model alone represents an incomplete simulation. One must also replicate the environment models (e.g., atmosphere, gravity, terrain) to achieve identical vehicle behavior across all applications. Environment models are increasing in complexity and represent a substantial investment to re-engineer for a new application. A software component that can be rehosted in each application is one solution to the deployment problem. The component must encapsulate both the vehicle and environment models. The component must have a well-defined interface that abstracts the bulk of the logic to operate the models. This paper examines the characteristics of a rehostable modeling component from the perspective of a human-in-the-loop simulation framework. The Langley Standard Real-Time Simulation in C++ (LaSRS++) is used as an example. LaSRS++ was recently redesigned to transform its modeling package into a rehostable component.

  12. Parallel methods for the flight simulation model

    SciTech Connect

    Xiong, Wei Zhong; Swietlik, C.

    1994-06-01

    The Advanced Computer Applications Center (ACAC) has been involved in evaluating advanced parallel architecture computers and the applicability of these machines to computer simulation models. The advanced systems investigated include parallel machines with shared. memory and distributed architectures consisting of an eight processor Alliant FX/8, a twenty four processor sor Sequent Symmetry, Cray XMP, IBM RISC 6000 model 550, and the Intel Touchstone eight processor Gamma and 512 processor Delta machines. Since parallelizing a truly efficient application program for the parallel machine is a difficult task, the implementation for these machines in a realistic setting has been largely overlooked. The ACAC has developed considerable expertise in optimizing and parallelizing application models on a collection of advanced multiprocessor systems. One of aspect of such an application model is the Flight Simulation Model, which used a set of differential equations to describe the flight characteristics of a launched missile by means of a trajectory. The Flight Simulation Model was written in the FORTRAN language with approximately 29,000 lines of source code. Depending on the number of trajectories, the computation can require several hours to full day of CPU time on DEC/VAX 8650 system. There is an impetus to reduce the execution time and utilize the advanced parallel architecture computing environment available. ACAC researchers developed a parallel method that allows the Flight Simulation Model to be able to run in parallel on the multiprocessor system. For the benchmark data tested, the parallel Flight Simulation Model implemented on the Alliant FX/8 has achieved nearly linear speedup. In this paper, we describe a parallel method for the Flight Simulation Model. We believe the method presented in this paper provides a general concept for the design of parallel applications. This concept, in most cases, can be adapted to many other sequential application programs.

  13. Revolutions in energy through modeling and simulation

    SciTech Connect

    Tatro, M.; Woodard, J.

    1998-08-01

    The development and application of energy technologies for all aspects from generation to storage have improved dramatically with the advent of advanced computational tools, particularly modeling and simulation. Modeling and simulation are not new to energy technology development, and have been used extensively ever since the first commercial computers were available. However, recent advances in computing power and access have broadened the extent and use, and, through increased fidelity (i.e., accuracy) of the models due to greatly enhanced computing power, the increased reliance on modeling and simulation has shifted the balance point between modeling and experimentation. The complex nature of energy technologies has motivated researchers to use these tools to understand better performance, reliability and cost issues related to energy. The tools originated in sciences such as the strength of materials (nuclear reactor containment vessels); physics, heat transfer and fluid flow (oil production); chemistry, physics, and electronics (photovoltaics); and geosciences and fluid flow (oil exploration and reservoir storage). Other tools include mathematics, such as statistics, for assessing project risks. This paper describes a few advancements made possible by these tools and explores the benefits and costs of their use, particularly as they relate to the acceleration of energy technology development. The computational complexity ranges from basic spreadsheets to complex numerical simulations using hardware ranging from personal computers (PCs) to Cray computers. In all cases, the benefits of using modeling and simulation relate to lower risks, accelerated technology development, or lower cost projects.

  14. Air target models for fuzing simulations

    NASA Astrophysics Data System (ADS)

    Dammann, J. F., Jr.

    1982-09-01

    Radar backscatter models for air targets suitable for computer simulation of radar fuze-air target encounters are described. These models determine the characteristics of the energy reflected to the fuze when the target is illuminated by a fuze radar. When the target models are coupled with fuze models, the time when the fuze detects the presence of the target can be determined for any arbitrary terminal encounter geometry. Fuze detection times for representative trajectories can be compared with fuze specifications to measure fuze performance or can be used as a part of a simulation of an entire system to determine system performance. Following one basic methodology, target models have been written for the Fishbed, Foxbat, and Flogger fighter aircraft; the Hind-D helicopter; and the Backfire, Blinder, and B-1 bombers. All of the models are specular point models where the major return is assumed to come from a small number of glitter points or specular points on the target.

  15. Modeling & Simulation Executive Agent Panel

    DTIC Science & Technology

    2007-11-02

    Richard W. ; 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME AND ADDRESS Office of the Oceanographer of the Navy...acquisition, and training communities.” MSEA Role • Facilitator in the project startup phase • Catalyst during development • Certifier in the...ACOUSTIC MODELS Parabolic Equation 5.0 ASTRAL 5.0 ASPM 4.3 Gaussian Ray Bundle 1.0 High Freq Env Acoustic (HFEVA) 1.0 COLOSSUS II 1.0 Low Freq Bottom LOSS

  16. Electrical Load Modeling and Simulation

    SciTech Connect

    Chassin, David P.

    2013-01-01

    Electricity consumer demand response and load control are playing an increasingly important role in the development of a smart grid. Smart grid load management technologies such as Grid FriendlyTM controls and real-time pricing are making their way into the conventional model of grid planning and operations. However, the behavior of load both affects, and is affected by load control strategies that are designed to support electric grid planning and operations. This chapter discussed the natural behavior of electric loads, how it interacts with various load control and demand response strategies, what the consequences are for new grid operation concepts and the computing issues these new technologies raise.

  17. Non-linear transformer modeling and simulation

    SciTech Connect

    Archer, W.E.; Deveney, M.F.; Nagel, R.L.

    1994-08-01

    Transformers models for simulation with Pspice and Analogy`s Saber are being developed using experimental B-H Loop and network analyzer measurements. The models are evaluated for accuracy and convergence using several test circuits. Results are presented which demonstrate the effects on circuit performance from magnetic core losses eddy currents and mechanical stress on the magnetic cores.

  18. Rotor systems research aircraft simulation mathematical model

    NASA Technical Reports Server (NTRS)

    Houck, J. A.; Moore, F. L.; Howlett, J. J.; Pollock, K. S.; Browne, M. M.

    1977-01-01

    An analytical model developed for evaluating and verifying advanced rotor concepts is discussed. The model was used during in both open loop and real time man-in-the-loop simulation during the rotor systems research aircraft design. Future applications include: pilot training, preflight of test programs, and the evaluation of promising concepts before their implementation on the flight vehicle.

  19. Estimating solar radiation for plant simulation models

    NASA Technical Reports Server (NTRS)

    Hodges, T.; French, V.; Leduc, S.

    1985-01-01

    Five algorithms producing daily solar radiation surrogates using daily temperatures and rainfall were evaluated using measured solar radiation data for seven U.S. locations. The algorithms were compared both in terms of accuracy of daily solar radiation estimates and terms of response when used in a plant growth simulation model (CERES-wheat). Requirements for accuracy of solar radiation for plant growth simulation models are discussed. One algorithm is recommended as being best suited for use in these models when neither measured nor satellite estimated solar radiation values are available.

  20. Molecular simulation and modeling of complex I.

    PubMed

    Hummer, Gerhard; Wikström, Mårten

    2016-07-01

    Molecular modeling and molecular dynamics simulations play an important role in the functional characterization of complex I. With its large size and complicated function, linking quinone reduction to proton pumping across a membrane, complex I poses unique modeling challenges. Nonetheless, simulations have already helped in the identification of possible proton transfer pathways. Simulations have also shed light on the coupling between electron and proton transfer, thus pointing the way in the search for the mechanistic principles underlying the proton pump. In addition to reviewing what has already been achieved in complex I modeling, we aim here to identify pressing issues and to provide guidance for future research to harness the power of modeling in the functional characterization of complex I. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.

  1. Mars Smart Lander Parachute Simulation Model

    NASA Technical Reports Server (NTRS)

    Queen, Eric M.; Raiszadeh, Ben

    2002-01-01

    A multi-body flight simulation for the Mars Smart Lander has been developed that includes six degree-of-freedom rigid-body models for both the supersonically-deployed and subsonically-deployed parachutes. This simulation is designed to be incorporated into a larger simulation of the entire entry, descent and landing (EDL) sequence. The complete end-to-end simulation will provide attitude history predictions of all bodies throughout the flight as well as loads on each of the connecting lines. Other issues such as recontact with jettisoned elements (heat shield, back shield, parachute mortar covers, etc.), design of parachute and attachment points, and desirable line properties can also be addressed readily using this simulation.

  2. PIXE simulation: Models, methods and technologies

    SciTech Connect

    Batic, M.; Pia, M. G.; Saracco, P.; Weidenspointner, G.

    2013-04-19

    The simulation of PIXE (Particle Induced X-ray Emission) is discussed in the context of general-purpose Monte Carlo systems for particle transport. Dedicated PIXE codes are mainly concerned with the application of the technique to elemental analysis, but they lack the capability of dealing with complex experimental configurations. General-purpose Monte Carlo codes provide powerful tools to model the experimental environment in great detail, but so far they have provided limited functionality for PIXE simulation. This paper reviews recent developments that have endowed the Geant4 simulation toolkit with advanced capabilities for PIXE simulation, and related efforts for quantitative validation of cross sections and other physical parameters relevant to PIXE simulation.

  3. A queuing model for road traffic simulation

    SciTech Connect

    Guerrouahane, N.; Aissani, D.; Bouallouche-Medjkoune, L.; Farhi, N.

    2015-03-10

    We present in this article a stochastic queuing model for the raod traffic. The model is based on the M/G/c/c state dependent queuing model, and is inspired from the deterministic Godunov scheme for the road traffic simulation. We first propose a variant of M/G/c/c state dependent model that works with density-flow fundamental diagrams rather than density-speed relationships. We then extend this model in order to consider upstream traffic demand as well as downstream traffic supply. Finally, we show how to model a whole raod by concatenating raod sections as in the deterministic Godunov scheme.

  4. Development of NASA's Models and Simulations Standard

    NASA Technical Reports Server (NTRS)

    Bertch, William J.; Zang, Thomas A.; Steele, Martin J.

    2008-01-01

    From the Space Shuttle Columbia Accident Investigation, there were several NASA-wide actions that were initiated. One of these actions was to develop a standard for development, documentation, and operation of Models and Simulations. Over the course of two-and-a-half years, a team of NASA engineers, representing nine of the ten NASA Centers developed a Models and Simulation Standard to address this action. The standard consists of two parts. The first is the traditional requirements section addressing programmatics, development, documentation, verification, validation, and the reporting of results from both the M&S analysis and the examination of compliance with this standard. The second part is a scale for evaluating the credibility of model and simulation results using levels of merit associated with 8 key factors. This paper provides an historical account of the challenges faced by and the processes used in this committee-based development effort. This account provides insights into how other agencies might approach similar developments. Furthermore, we discuss some specific applications of models and simulations used to assess the impact of this standard on future model and simulation activities.

  5. Model Validation for Simulations of Vehicle Systems

    DTIC Science & Technology

    2012-08-01

    a large number of replicate samples via Monte- Carlo simulation. The test data, on the other hand, is usually provided as a collection of point...can be determined by Monte Carlo simulation. Classical hypothesis testing techniques depend on a normality assumption except for the modified...criteria”, Computer Methods in Applied Mechanics and Engineering, 197:2517-2539, 2008. [14] S. Ferson, W. L. Oberkampf and L. Ginzburg , “Model

  6. Water system modeling for dispatcher training simulators

    SciTech Connect

    Rajagopal, S.; Sigari, P.G. ); Allen, J.E.; Assadian, M. )

    1993-08-01

    This paper addresses the existing need for training dispatchers in the operation of power systems where it involves managing large water systems. The problem formulation and implementation of water system modeling for the Dispatcher Training Simulators (DTS) are presented in this paper. The method systematically builds the water network descriptions. The model periodically calculates the water system flows, storage values, and currently available hydro generation capacities. The model is controllable by the instructor and provides the simulated telemetry of water system data to the control center functions in the DTS. The water system modeling enhances the power system modeling subsystem of the DTS. The method is validated on a large water system and power system data. The results and the benefits of water system modeling are discussed.

  7. Simulation Modeling of Software Development Processes

    NASA Technical Reports Server (NTRS)

    Calavaro, G. F.; Basili, V. R.; Iazeolla, G.

    1996-01-01

    A simulation modeling approach is proposed for the prediction of software process productivity indices, such as cost and time-to-market, and the sensitivity analysis of such indices to changes in the organization parameters and user requirements. The approach uses a timed Petri Net and Object Oriented top-down model specification. Results demonstrate the model representativeness, and its usefulness in verifying process conformance to expectations, and in performing continuous process improvement and optimization.

  8. Incorporation of RAM techniques into simulation modeling

    SciTech Connect

    Nelson, S.C. Jr.; Haire, M.J.; Schryver, J.C.

    1995-07-01

    This work concludes that reliability, availability, and maintainability (RAM) analytical techniques can be incorporated into computer network simulation modeling to yield an important new analytical tool. This paper describes the incorporation of failure and repair information into network simulation to build a stochastic computer model represents the RAM Performance of two vehicles being developed for the US Army: The Advanced Field Artillery System (AFAS) and the Future Armored Resupply Vehicle (FARV). The AFAS is the US Army`s next generation self-propelled cannon artillery system. The FARV is a resupply vehicle for the AFAS. Both vehicles utilize automation technologies to improve the operational performance of the vehicles and reduce manpower. The network simulation model used in this work is task based. The model programmed in this application requirements a typical battle mission and the failures and repairs that occur during that battle. Each task that the FARV performs--upload, travel to the AFAS, refuel, perform tactical/survivability moves, return to logistic resupply, etc.--is modeled. Such a model reproduces a model reproduces operational phenomena (e.g., failures and repairs) that are likely to occur in actual performance. Simulation tasks are modeled as discrete chronological steps; after the completion of each task decisions are programmed that determine the next path to be followed. The result is a complex logic diagram or network. The network simulation model is developed within a hierarchy of vehicle systems, subsystems, and equipment and includes failure management subnetworks. RAM information and other performance measures are collected which have impact on design requirements. Design changes are evaluated through ``what if`` questions, sensitivity studies, and battle scenario changes.

  9. Analyzing Strategic Business Rules through Simulation Modeling

    NASA Astrophysics Data System (ADS)

    Orta, Elena; Ruiz, Mercedes; Toro, Miguel

    Service Oriented Architecture (SOA) holds promise for business agility since it allows business process to change to meet new customer demands or market needs without causing a cascade effect of changes in the underlying IT systems. Business rules are the instrument chosen to help business and IT to collaborate. In this paper, we propose the utilization of simulation models to model and simulate strategic business rules that are then disaggregated at different levels of an SOA architecture. Our proposal is aimed to help find a good configuration for strategic business objectives and IT parameters. The paper includes a case study where a simulation model is built to help business decision-making in a context where finding a good configuration for different business parameters and performance is too complex to analyze by trial and error.

  10. Distributed earth model/orbiter simulation

    NASA Technical Reports Server (NTRS)

    Geisler, Erik; Mcclanahan, Scott; Smith, Gary

    1989-01-01

    Distributed Earth Model/Orbiter Simulation (DEMOS) is a network based application developed for the UNIX environment that visually monitors or simulates the Earth and any number of orbiting vehicles. Its purpose is to provide Mission Control Center (MCC) flight controllers with a visually accurate three dimensional (3D) model of the Earth, Sun, Moon and orbiters, driven by real time or simulated data. The project incorporates a graphical user interface, 3D modelling employing state-of-the art hardware, and simulation of orbital mechanics in a networked/distributed environment. The user interface is based on the X Window System and the X Ray toolbox. The 3D modelling utilizes the Programmer's Hierarchical Interactive Graphics System (PHIGS) standard and Raster Technologies hardware for rendering/display performance. The simulation of orbiting vehicles uses two methods of vector propagation implemented with standard UNIX/C for portability. Each part is a distinct process that can run on separate nodes of a network, exploiting each node's unique hardware capabilities. The client/server communication architecture of the application can be reused for a variety of distributed applications.

  11. Common modeling system for digital simulation

    NASA Technical Reports Server (NTRS)

    Painter, Rick

    1994-01-01

    The Joint Modeling and Simulation System is a tri-service investigation into a common modeling framework for the development digital models. The basis for the success of this framework is an X-window-based, open systems architecture, object-based/oriented methodology, standard interface approach to digital model construction, configuration, execution, and post processing. For years Department of Defense (DOD) agencies have produced various weapon systems/technologies and typically digital representations of the systems/technologies. These digital representations (models) have also been developed for other reasons such as studies and analysis, Cost Effectiveness Analysis (COEA) tradeoffs, etc. Unfortunately, there have been no Modeling and Simulation (M&S) standards, guidelines, or efforts towards commonality in DOD M&S. The typical scenario is an organization hires a contractor to build hardware and in doing so an digital model may be constructed. Until recently, this model was not even obtained by the organization. Even if it was procured, it was on a unique platform, in a unique language, with unique interfaces, and, with the result being UNIQUE maintenance required. Additionally, the constructors of the model expended more effort in writing the 'infrastructure' of the model/simulation (e.g. user interface, database/database management system, data journalizing/archiving, graphical presentations, environment characteristics, other components in the simulation, etc.) than in producing the model of the desired system. Other side effects include: duplication of efforts; varying assumptions; lack of credibility/validation; and decentralization in policy and execution. J-MASS provides the infrastructure, standards, toolset, and architecture to permit M&S developers and analysts to concentrate on the their area of interest.

  12. Battery thermal models for hybrid vehicle simulations

    NASA Astrophysics Data System (ADS)

    Pesaran, Ahmad A.

    This paper summarizes battery thermal modeling capabilities for: (1) an advanced vehicle simulator (ADVISOR); and (2) battery module and pack thermal design. The National Renewable Energy Laboratory's (NREL's) ADVISOR is developed in the Matlab/Simulink environment. There are several battery models in ADVISOR for various chemistry types. Each one of these models requires a thermal model to predict the temperature change that could affect battery performance parameters, such as resistance, capacity and state of charges. A lumped capacitance battery thermal model in the Matlab/Simulink environment was developed that included the ADVISOR battery performance models. For thermal evaluation and design of battery modules and packs, NREL has been using various computer aided engineering tools including commercial finite element analysis software. This paper will discuss the thermal ADVISOR battery model and its results, along with the results of finite element modeling that were presented at the workshop on "Development of Advanced Battery Engineering Models" in August 2001.

  13. Damage modeling for Taylor impact simulations

    NASA Astrophysics Data System (ADS)

    Anderson, C. E., Jr.; Chocron, I. S.; Nicholls, A. E.

    2006-08-01

    G. I. Taylor showed that dynamic material properties could be deduced from the impact of a projectile against a rigid boundary. The Taylor anvil test became very useful with the advent of numerical simulations and has been used to infer and/or to validate material constitutive constants. A new experimental facility has been developed to conduct Taylor anvil impacts to support validation of constitutive constants used in simulations. Typically, numerical simulations are conducted assuming 2-D cylindrical symmetry, but such computations cannot hope to capture the damage observed in higher velocity experiments. A computational study was initiated to examine the ability to simulate damage and subsequent deformation of the Taylor specimens. Three-dimensional simulations, using the Johnson-Cook damage model, were conducted with the nonlinear Eulerian wavecode CTH. The results of the simulations are compared to experimental deformations of 6061-T6 aluminum specimens as a function of impact velocity, and conclusions regarding the ability to simulate fracture and reproduce the observed deformations are summarized.

  14. Observation simulation experiments with regional prediction models

    NASA Technical Reports Server (NTRS)

    Diak, George; Perkey, Donald J.; Kalb, Michael; Robertson, Franklin R.; Jedlovec, Gary

    1990-01-01

    Research efforts in FY 1990 included studies employing regional scale numerical models as aids in evaluating potential contributions of specific satellite observing systems (current and future) to numerical prediction. One study involves Observing System Simulation Experiments (OSSEs) which mimic operational initialization/forecast cycles but incorporate simulated Advanced Microwave Sounding Unit (AMSU) radiances as input data. The objective of this and related studies is to anticipate the potential value of data from these satellite systems, and develop applications of remotely sensed data for the benefit of short range forecasts. Techniques are also being used that rely on numerical model-based synthetic satellite radiances to interpret the information content of various types of remotely sensed image and sounding products. With this approach, evolution of simulated channel radiance image features can be directly interpreted in terms of the atmospheric dynamical processes depicted by a model. Progress is being made in a study using the internal consistency of a regional prediction model to simplify the assessment of forced diabatic heating and moisture initialization in reducing model spinup times. Techniques for model initialization are being examined, with focus on implications for potential applications of remote microwave observations, including AMSU and Special Sensor Microwave Imager (SSM/I), in shortening model spinup time for regional prediction.

  15. Thermohydraulic modeling and simulation of breeder reactors

    SciTech Connect

    Agrawal, A.K.; Khatib-Rahbar, M.; Curtis, R.T.; Hetrick, D.L.; Girijashankar, P.V.

    1982-01-01

    This paper deals with the modeling and simulation of system-wide transients in LMFBRs. Unprotected events (i.e., the presumption of failure of the plant protection system) leading to core-melt are not considered in this paper. The existing computational capabilities in the area of protected transients in the US are noted. Various physical and numerical approximations that are made in these codes are discussed. Finally, the future direction in the area of model verification and improvements is discussed.

  16. Modeling and Simulation of Count Data

    PubMed Central

    Plan, E L

    2014-01-01

    Count data, or number of events per time interval, are discrete data arising from repeated time to event observations. Their mean count, or piecewise constant event rate, can be evaluated by discrete probability distributions from the Poisson model family. Clinical trial data characterization often involves population count analysis. This tutorial presents the basics and diagnostics of count modeling and simulation in the context of pharmacometrics. Consideration is given to overdispersion, underdispersion, autocorrelation, and inhomogeneity. PMID:25116273

  17. Love Kills:. Simulations in Penna Ageing Model

    NASA Astrophysics Data System (ADS)

    Stauffer, Dietrich; Cebrat, Stanisław; Penna, T. J. P.; Sousa, A. O.

    The standard Penna ageing model with sexual reproduction is enlarged by adding additional bit-strings for love: Marriage happens only if the male love strings are sufficiently different from the female ones. We simulate at what level of required difference the population dies out.

  18. Center for Advanced Modeling and Simulation Intern

    SciTech Connect

    Gertman, Vanessa

    2010-01-01

    Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

  19. Using Simulation Models in Demonstrating Statistical Applications.

    ERIC Educational Resources Information Center

    Schuermann, Allen C.; Hommertzheim, Donald L.

    1983-01-01

    Describes five statistical simulation programs developed at Wichita State University--Coin Flip and Raindrop, which demonstrate the binomial, Poisson, and other related distributions; Optimal Search; QSIM; and RANDEV, a random deviate generation program. Advantages of microcomputers over mainframes and the educational uses of models are noted.…

  20. Simulation Modeling on the Macintosh using STELLA.

    ERIC Educational Resources Information Center

    Costanza, Robert

    1987-01-01

    Describes a new software package for the Apple Macintosh computer which can be used to create elaborate simulation models in a fraction of the time usually required without using a programming language. Illustrates the use of the software which relates to water usage. (TW)

  1. Catalog of Wargaming and Military Simulation Models.

    DTIC Science & Technology

    1982-05-01

    production by industries; sub-titutions of raw materials, energy, inteniiediate goods, and finished products; investment, employment; 235 technology ...Interindustry, Equilibrium, Dynamic, Simulatior, Substitution, Technology , Model, and Economic 238 TITLE: Direct Fire Simulation (BRONZE SCEPTRE I Version...input-output techniques which allow no changes in relative prices and technology and no substitution of inputs or outputs. From that standpoint, it

  2. Simulation Versus Models: Which One and When?

    ERIC Educational Resources Information Center

    Dorn, William S.

    1975-01-01

    Describes two types of computer-based experiments: simulation (which assumes no student knowledge of the workings of the computer program) is recommended for experiments aimed at inductive reasoning; and modeling (which assumes student understanding of the computer program) is recommended for deductive processes. (MLH)

  3. Center for Advanced Modeling and Simulation Intern

    ScienceCinema

    Gertman, Vanessa

    2016-07-12

    Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

  4. Adaptive System Modeling for Spacecraft Simulation

    NASA Technical Reports Server (NTRS)

    Thomas, Justin

    2011-01-01

    This invention introduces a methodology and associated software tools for automatically learning spacecraft system models without any assumptions regarding system behavior. Data stream mining techniques were used to learn models for critical portions of the International Space Station (ISS) Electrical Power System (EPS). Evaluation on historical ISS telemetry data shows that adaptive system modeling reduces simulation error anywhere from 50 to 90 percent over existing approaches. The purpose of the methodology is to outline how someone can create accurate system models from sensor (telemetry) data. The purpose of the software is to support the methodology. The software provides analysis tools to design the adaptive models. The software also provides the algorithms to initially build system models and continuously update them from the latest streaming sensor data. The main strengths are as follows: Creates accurate spacecraft system models without in-depth system knowledge or any assumptions about system behavior. Automatically updates/calibrates system models using the latest streaming sensor data. Creates device specific models that capture the exact behavior of devices of the same type. Adapts to evolving systems. Can reduce computational complexity (faster simulations).

  5. Twitter's tweet method modelling and simulation

    NASA Astrophysics Data System (ADS)

    Sarlis, Apostolos S.; Sakas, Damianos P.; Vlachos, D. S.

    2015-02-01

    This paper seeks to purpose the concept of Twitter marketing methods. The tools that Twitter provides are modelled and simulated using iThink in the context of a Twitter media-marketing agency. The paper has leveraged the system's dynamic paradigm to conduct Facebook marketing tools and methods modelling, using iThink™ system to implement them. It uses the design science research methodology for the proof of concept of the models and modelling processes. The following models have been developed for a twitter marketing agent/company and tested in real circumstances and with real numbers. These models were finalized through a number of revisions and iterators of the design, develop, simulate, test and evaluate. It also addresses these methods that suit most organized promotion through targeting, to the Twitter social media service. The validity and usefulness of these Twitter marketing methods models for the day-to-day decision making are authenticated by the management of the company organization. It implements system dynamics concepts of Twitter marketing methods modelling and produce models of various Twitter marketing situations. The Tweet method that Twitter provides can be adjusted, depending on the situation, in order to maximize the profit of the company/agent.

  6. Computational Spectrum of Agent Model Simulation

    SciTech Connect

    Perumalla, Kalyan S

    2010-01-01

    The study of human social behavioral systems is finding renewed interest in military, homeland security and other applications. Simulation is the most generally applied approach to studying complex scenarios in such systems. Here, we outline some of the important considerations that underlie the computational aspects of simulation-based study of human social systems. The fundamental imprecision underlying questions and answers in social science makes it necessary to carefully distinguish among different simulation problem classes and to identify the most pertinent set of computational dimensions associated with those classes. We identify a few such classes and present their computational implications. The focus is then shifted to the most challenging combinations in the computational spectrum, namely, large-scale entity counts at moderate to high levels of fidelity. Recent developments in furthering the state-of-the-art in these challenging cases are outlined. A case study of large-scale agent simulation is provided in simulating large numbers (millions) of social entities at real-time speeds on inexpensive hardware. Recent computational results are identified that highlight the potential of modern high-end computing platforms to push the envelope with respect to speed, scale and fidelity of social system simulations. Finally, the problem of shielding the modeler or domain expert from the complex computational aspects is discussed and a few potential solution approaches are identified.

  7. Advances in NLTE Modeling for Integrated Simulations

    SciTech Connect

    Scott, H A; Hansen, S B

    2009-07-08

    The last few years have seen significant progress in constructing the atomic models required for non-local thermodynamic equilibrium (NLTE) simulations. Along with this has come an increased understanding of the requirements for accurately modeling the ionization balance, energy content and radiative properties of different elements for a wide range of densities and temperatures. Much of this progress is the result of a series of workshops dedicated to comparing the results from different codes and computational approaches applied to a series of test problems. The results of these workshops emphasized the importance of atomic model completeness, especially in doubly excited states and autoionization transitions, to calculating ionization balance, and the importance of accurate, detailed atomic data to producing reliable spectra. We describe a simple screened-hydrogenic model that calculates NLTE ionization balance with surprising accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes. The model incorporates term splitting, {Delta}n = 0 transitions, and approximate UTA widths for spectral calculations, with results comparable to those of much more detailed codes. Simulations done with this model have been increasingly successful at matching experimental data for laser-driven systems and hohlraums. Accurate and efficient atomic models are just one requirement for integrated NLTE simulations. Coupling the atomic kinetics to hydrodynamics and radiation transport constrains both discretizations and algorithms to retain energy conservation, accuracy and stability. In particular, the strong coupling between radiation and populations can require either very short timesteps or significantly modified radiation transport algorithms to account for NLTE material response. Considerations such as these continue to provide challenges for NLTE simulations.

  8. Fault diagnosis based on continuous simulation models

    NASA Technical Reports Server (NTRS)

    Feyock, Stefan

    1987-01-01

    The results are described of an investigation of techniques for using continuous simulation models as basis for reasoning about physical systems, with emphasis on the diagnosis of system faults. It is assumed that a continuous simulation model of the properly operating system is available. Malfunctions are diagnosed by posing the question: how can we make the model behave like that. The adjustments that must be made to the model to produce the observed behavior usually provide definitive clues to the nature of the malfunction. A novel application of Dijkstra's weakest precondition predicate transformer is used to derive the preconditions for producing the required model behavior. To minimize the size of the search space, an envisionment generator based on interval mathematics was developed. In addition to its intended application, the ability to generate qualitative state spaces automatically from quantitative simulations proved to be a fruitful avenue of investigation in its own right. Implementations of the Dijkstra transform and the envisionment generator are reproduced in the Appendix.

  9. Modeling and simulation of magnetic nanoparticle sensor.

    PubMed

    Makiranta, Jarkko; Lekkala, Jukka

    2005-01-01

    Sensitivity and detection limit of a magnetic nanoparticle sensor is modeled and simulated. A micro coil generates an alternating magnetic field which excites magnetic nanoparticles in its vicinity. A concentric sensing coil applies Faraday's law of induction measuring the excited magnetization of the magnetic particles at high frequency. A differential measurement compensates disturbances and the influence of the driving microcoil leaving only the signal caused by the magnetic particles. The sensing system can be used for detection of magnetic nanoparticle labels in immunological point of care diagnostics. The paper shows simulation results for a microcoil system capable of detecting a single superparamagnetic nanoparticle.

  10. Compressible homogeneous shear: Simulation and modeling

    NASA Technical Reports Server (NTRS)

    Sarkar, S.; Erlebacher, G.; Hussaini, M. Y.

    1992-01-01

    Compressibility effects were studied on turbulence by direct numerical simulation of homogeneous shear flow. A primary observation is that the growth of the turbulent kinetic energy decreases with increasing turbulent Mach number. The sinks provided by compressible dissipation and the pressure dilatation, along with reduced Reynolds shear stress, are shown to contribute to the reduced growth of kinetic energy. Models are proposed for these dilatational terms and verified by direct comparison with the simulations. The differences between the incompressible and compressible fields are brought out by the examination of spectra, statistical moments, and structure of the rate of strain tensor.

  11. Flight Simulation Model Exchange. Volume 2; Appendices

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.; Jackson, E. Bruce

    2011-01-01

    The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the appendices to the main report.

  12. Flight Simulation Model Exchange. Volume 1

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.; Jackson, E. Bruce

    2011-01-01

    The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the results of the assessment.

  13. Deep Drawing Simulations With Different Polycrystalline Models

    NASA Astrophysics Data System (ADS)

    Duchêne, Laurent; de Montleau, Pierre; Bouvier, Salima; Habraken, Anne Marie

    2004-06-01

    The goal of this research is to study the anisotropic material behavior during forming processes, represented by both complex yield loci and kinematic-isotropic hardening models. A first part of this paper describes the main concepts of the `Stress-strain interpolation' model that has been implemented in the non-linear finite element code Lagamine. This model consists of a local description of the yield locus based on the texture of the material through the full constraints Taylor's model. The texture evolution due to plastic deformations is computed throughout the FEM simulations. This `local yield locus' approach was initially linked to the classical isotropic Swift hardening law. Recently, a more complex hardening model was implemented: the physically-based microstructural model of Teodosiu. It takes into account intergranular heterogeneity due to the evolution of dislocation structures, that affects isotropic and kinematic hardening. The influence of the hardening model is compared to the influence of the texture evolution thanks to deep drawing simulations.

  14. Facebook's personal page modelling and simulation

    NASA Astrophysics Data System (ADS)

    Sarlis, Apostolos S.; Sakas, Damianos P.; Vlachos, D. S.

    2015-02-01

    In this paper we will try to define the utility of Facebook's Personal Page marketing method. This tool that Facebook provides, is modelled and simulated using iThink in the context of a Facebook marketing agency. The paper has leveraged the system's dynamic paradigm to conduct Facebook marketing tools and methods modelling, using iThink™ system to implement them. It uses the design science research methodology for the proof of concept of the models and modelling processes. The following model has been developed for a social media marketing agent/company, Facebook platform oriented and tested in real circumstances. This model is finalized through a number of revisions and iterators of the design, development, simulation, testing and evaluation processes. The validity and usefulness of this Facebook marketing model for the day-to-day decision making are authenticated by the management of the company organization. Facebook's Personal Page method can be adjusted, depending on the situation, in order to maximize the total profit of the company which is to bring new customers, keep the interest of the old customers and deliver traffic to its website.

  15. Towards Better Coupling of Hydrological Simulation Models

    NASA Astrophysics Data System (ADS)

    Penton, D.; Stenson, M.; Leighton, B.; Bridgart, R.

    2012-12-01

    Standards for model interoperability and scientific workflow software provide techniques and tools for coupling hydrological simulation models. However, model builders are yet to realize the benefits of these and continue to write ad hoc implementations and scripts. Three case studies demonstrate different approaches to coupling models, the first using tight interfaces (OpenMI), the second using a scientific workflow system (Trident) and the third using a tailored execution engine (Delft Flood Early Warning System - Delft-FEWS). No approach was objectively better than any other approach. The foremost standard for coupling hydrological models is the Open Modeling Interface (OpenMI), which defines interfaces for models to interact. An implementation of the OpenMI standard involves defining interchange terms and writing a .NET/Java wrapper around the model. An execution wrapper such as OatC.GUI or Pipistrelle executes the models. The team built two OpenMI implementations for eWater Source river system models. Once built, it was easy to swap river system models. The team encountered technical challenges with versions of the .Net framework (3.5 calling 4.0) and with the performance of the execution wrappers when running daily simulations. By design, the OpenMI interfaces are general, leaving significant decisions around the semantics of the interfaces to the implementer. Increasingly, scientific workflow tools such as Kepler, Taverna and Trident are able to replace custom scripts. These tools aim to improve the provenance and reproducibility of processing tasks. In particular, Taverna and the myExperiment website have had success making many bioinformatics workflows reusable and sharable. The team constructed Trident activities for hydrological software including IQQM, REALM and eWater Source. They built an activity generator for model builders to build activities for particular river systems. The models were linked at a simulation level, without any daily time

  16. Modeling and simulation of the human eye

    NASA Astrophysics Data System (ADS)

    Duran, R.; Ventura, L.; Nonato, L.; Bruno, O.

    2007-02-01

    The computational modeling of the human eye has been wide studied for different sectors of the scientific and technological community. One of the main reasons for this increasing interest is the possibility to reproduce eye optic properties by means of computational simulations, becoming possible the development of efficient devices to treat and to correct the problems of the vision. This work explores this aspect still little investigated of the modeling of the visual system, considering a computational sketch that make possible the use of real data in the modeling and simulation of the human visual system. This new approach makes possible the individual inquiry of the optic system, assisting in the construction of new techniques used to infer vital data in medical investigations. Using corneal topography to collect real data from patients, a computational model of cornea is constructed and a set of simulations were build to ensure the correctness of the system and to investigate the effect of corneal abnormalities in retinal image formation, such as Plcido Discs, Point Spread Function, Wave front and the projection of a real image and it's visualization on retina.

  17. Theory, modeling and simulation: Annual report 1993

    SciTech Connect

    Dunning, T.H. Jr.; Garrett, B.C.

    1994-07-01

    Developing the knowledge base needed to address the environmental restoration issues of the US Department of Energy requires a fundamental understanding of molecules and their interactions in insolation and in liquids, on surfaces, and at interfaces. To meet these needs, the PNL has established the Environmental and Molecular Sciences Laboratory (EMSL) and will soon begin construction of a new, collaborative research facility devoted to advancing the understanding of environmental molecular science. Research in the Theory, Modeling, and Simulation program (TMS), which is one of seven research directorates in the EMSL, will play a critical role in understanding molecular processes important in restoring DOE`s research, development and production sites, including understanding the migration and reactions of contaminants in soils and groundwater, the development of separation process for isolation of pollutants, the development of improved materials for waste storage, understanding the enzymatic reactions involved in the biodegradation of contaminants, and understanding the interaction of hazardous chemicals with living organisms. The research objectives of the TMS program are to apply available techniques to study fundamental molecular processes involved in natural and contaminated systems; to extend current techniques to treat molecular systems of future importance and to develop techniques for addressing problems that are computationally intractable at present; to apply molecular modeling techniques to simulate molecular processes occurring in the multispecies, multiphase systems characteristic of natural and polluted environments; and to extend current molecular modeling techniques to treat complex molecular systems and to improve the reliability and accuracy of such simulations. The program contains three research activities: Molecular Theory/Modeling, Solid State Theory, and Biomolecular Modeling/Simulation. Extended abstracts are presented for 89 studies.

  18. eShopper modeling and simulation

    NASA Astrophysics Data System (ADS)

    Petrushin, Valery A.

    2001-03-01

    The advent of e-commerce gives an opportunity to shift the paradigm of customer communication into a highly interactive mode. The new generation of commercial Web servers, such as the Blue Martini's server, combines the collection of data on a customer behavior with real-time processing and dynamic tailoring of a feedback page. The new opportunities for direct product marketing and cross selling are arriving. The key problem is what kind of information do we need to achieve these goals, or in other words, how do we model the customer? The paper is devoted to customer modeling and simulation. The focus is on modeling an individual customer. The model is based on the customer's transaction data, click stream data, and demographics. The model includes the hierarchical profile of a customer's preferences to different types of products and brands; consumption models for the different types of products; the current focus, trends, and stochastic models for time intervals between purchases; product affinity models; and some generalized features, such as purchasing power, sensitivity to advertising, price sensitivity, etc. This type of model is used for predicting the date of the next visit, overall spending, and spending for different types of products and brands. For some type of stores (for example, a supermarket) and stable customers, it is possible to forecast the shopping lists rather accurately. The forecasting techniques are discussed. The forecasting results can be used for on- line direct marketing, customer retention, and inventory management. The customer model can also be used as a generative model for simulating the customer's purchasing behavior in different situations and for estimating customer's features.

  19. Simulation model of clastic sedimentary processes

    SciTech Connect

    Tetzlaff, D.M.

    1987-01-01

    This dissertation describes SEDSIM, a computer model that simulates erosion, transport, and deposition of clastic sediments by free-surface flow in natural environments. SEDSIM is deterministic and is applicable to sedimentary processes in rivers, deltas, continental shelves, submarine canyons, and turbidite fans. The model is used to perform experiments in clastic sedimentation. Computer experimentation is limited by computing power available, but is free from scaling problems associated with laboratory experiments. SEDSIM responds to information provided to it at the outset of a simulation experiment, including topography, subsurface configuration, physical parameters of fluid and sediment, and characteristics of sediment sources. Extensive computer graphics are incorporated in SEDSIM. The user can display the three-dimensional geometry of simulated deposits in the form of successions of contour maps, perspective diagrams, vector plots of current velocities, and vertical sections of any azimuth orientation. The sections show both sediment age and composition. SEDSIM works realistically with processes involving channel shifting and topographic changes. Example applications include simulation of an ancient submarine canyon carved into a Cretaceous sequence in the National Petroleum Reserve in Alaska, known mainly from seismic sections and a sequence of Tertiary age in the Golden Meadow oil field of Louisiana, known principally from well logs.

  20. Consequence modeling using the fire dynamics simulator.

    PubMed

    Ryder, Noah L; Sutula, Jason A; Schemel, Christopher F; Hamer, Andrew J; Van Brunt, Vincent

    2004-11-11

    The use of Computational Fluid Dynamics (CFD) and in particular Large Eddy Simulation (LES) codes to model fires provides an efficient tool for the prediction of large-scale effects that include plume characteristics, combustion product dispersion, and heat effects to adjacent objects. This paper illustrates the strengths of the Fire Dynamics Simulator (FDS), an LES code developed by the National Institute of Standards and Technology (NIST), through several small and large-scale validation runs and process safety applications. The paper presents two fire experiments--a small room fire and a large (15 m diameter) pool fire. The model results are compared to experimental data and demonstrate good agreement between the models and data. The validation work is then extended to demonstrate applicability to process safety concerns by detailing a model of a tank farm fire and a model of the ignition of a gaseous fuel in a confined space. In this simulation, a room was filled with propane, given time to disperse, and was then ignited. The model yields accurate results of the dispersion of the gas throughout the space. This information can be used to determine flammability and explosive limits in a space and can be used in subsequent models to determine the pressure and temperature waves that would result from an explosion. The model dispersion results were compared to an experiment performed by Factory Mutual. Using the above examples, this paper will demonstrate that FDS is ideally suited to build realistic models of process geometries in which large scale explosion and fire failure risks can be evaluated with several distinct advantages over more traditional CFD codes. Namely transient solutions to fire and explosion growth can be produced with less sophisticated hardware (lower cost) than needed for traditional CFD codes (PC type computer verses UNIX workstation) and can be solved for longer time histories (on the order of hundreds of seconds of computed time) with

  1. Macro Level Simulation Model Of Space Shuttle Processing

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The contents include: 1) Space Shuttle Processing Simulation Model; 2) Knowledge Acquisition; 3) Simulation Input Analysis; 4) Model Applications in Current Shuttle Environment; and 5) Model Applications for Future Reusable Launch Vehicles (RLV's). This paper is presented in viewgraph form.

  2. Advanced Modeling, Simulation and Analysis (AMSA) Capability Roadmap Progress Review

    NASA Technical Reports Server (NTRS)

    Antonsson, Erik; Gombosi, Tamas

    2005-01-01

    Contents include the following: NASA capability roadmap activity. Advanced modeling, simulation, and analysis overview. Scientific modeling and simulation. Operations modeling. Multi-special sensing (UV-gamma). System integration. M and S Environments and Infrastructure.

  3. Simulating Spin Models on Gpu: a Tour

    NASA Astrophysics Data System (ADS)

    Weigel, Martin

    2012-08-01

    The use of graphics processing units (GPUs) in scientific computing has gathered considerable momentum in the past five years. While GPUs in general promise high performance and excellent performance per Watt ratios, not every class of problems is equally well suitable for exploiting the massively parallel architecture they provide. Lattice spin models appear to be prototypic examples of problems suitable for this architecture, at least as long as local update algorithms are employed. In this review, I summarize our recent experience with the simulation of a wide range of spin models on GPU employing an equally wide range of update algorithms, ranging from Metropolis and heat bath updates, over cluster algorithms to generalized ensemble simulations.

  4. Model parameters for simulation of physiological lipids

    PubMed Central

    McGlinchey, Nicholas

    2016-01-01

    Coarse grain simulation of proteins in their physiological membrane environment can offer insight across timescales, but requires a comprehensive force field. Parameters are explored for multicomponent bilayers composed of unsaturated lipids DOPC and DOPE, mixed‐chain saturation POPC and POPE, and anionic lipids found in bacteria: POPG and cardiolipin. A nonbond representation obtained from multiscale force matching is adapted for these lipids and combined with an improved bonding description of cholesterol. Equilibrating the area per lipid yields robust bilayer simulations and properties for common lipid mixtures with the exception of pure DOPE, which has a known tendency to form nonlamellar phase. The models maintain consistency with an existing lipid–protein interaction model, making the force field of general utility for studying membrane proteins in physiologically representative bilayers. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26864972

  5. High-Fidelity Roadway Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Wang, Jie; Papelis, Yiannis; Shen, Yuzhong; Unal, Ozhan; Cetin, Mecit

    2010-01-01

    Roads are an essential feature in our daily lives. With the advances in computing technologies, 2D and 3D road models are employed in many applications, such as computer games and virtual environments. Traditional road models were generated by professional artists manually using modeling software tools such as Maya and 3ds Max. This approach requires both highly specialized and sophisticated skills and massive manual labor. Automatic road generation based on procedural modeling can create road models using specially designed computer algorithms or procedures, reducing the tedious manual editing needed for road modeling dramatically. But most existing procedural modeling methods for road generation put emphasis on the visual effects of the generated roads, not the geometrical and architectural fidelity. This limitation seriously restricts the applicability of the generated road models. To address this problem, this paper proposes a high-fidelity roadway generation method that takes into account road design principles practiced by civil engineering professionals, and as a result, the generated roads can support not only general applications such as games and simulations in which roads are used as 3D assets, but also demanding civil engineering applications, which requires accurate geometrical models of roads. The inputs to the proposed method include road specifications, civil engineering road design rules, terrain information, and surrounding environment. Then the proposed method generates in real time 3D roads that have both high visual and geometrical fidelities. This paper discusses in details the procedures that convert 2D roads specified in shape files into 3D roads and civil engineering road design principles. The proposed method can be used in many applications that have stringent requirements on high precision 3D models, such as driving simulations and road design prototyping. Preliminary results demonstrate the effectiveness of the proposed method.

  6. Difficulties with True Interoperability in Modeling & Simulation

    DTIC Science & Technology

    2011-12-01

    Standards in M&S cover multiple layers of technical abstraction. There are middleware specifica- tions, such as the High Level Architecture (HLA) ( IEEE Xplore ... IEEE Xplore Digital Library. 2010. 1516-2010 IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) – Framework and Rules...using different communication protocols being able to allow da- 2642978-1-4577-2109-0/11/$26.00 ©2011 IEEE Report Documentation Page Form ApprovedOMB No

  7. Refined Transistor Model For Simulation Of SEU

    NASA Technical Reports Server (NTRS)

    Zoutendyk, John A.; Benumof, Reuben

    1988-01-01

    Equivalent base resistance added. Theoretical study develops equations for parameters of Gummel-Poon model of bipolar junction transistor: includes saturation current, amplification factors, charging times, knee currents, capacitances, and resistances. Portion of study concerned with base region goes beyond Gummel-Poon analysis to provide more complete understanding of transistor behavior. Extended theory useful in simulation of single-event upset (SEU) caused in logic circuits by cosmic rays or other ionizing radiation.

  8. Theory, Modeling and Simulation Annual Report 2000

    SciTech Connect

    Dixon, David A.; Garrett, Bruce C.; Straatsma, Tp; Jones, Donald R.; Studham, Ronald S.; Harrison, Robert J.; Nichols, Jeffrey A.

    2001-11-01

    This annual report describes the 2000 research accomplishments for the Theory, Modeling, and Simulation (TM&S) directorate, one of the six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). EMSL is a U.S. Department of Energy (DOE) national scientific user facility and is the centerpiece of the DOE commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems.

  9. Theory, Modeling and Simulation Annual Report 2000

    SciTech Connect

    Dixon, David A; Garrett, Bruce C; Straatsma, TP; Jones, Donald R; Studham, Scott; Harrison, Robert J; Nichols, Jeffrey A

    2001-11-01

    This annual report describes the 2000 research accomplishments for the Theory, Modeling, and Simulation (TM and S) directorate, one of the six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). EMSL is a U.S. Department of Energy (DOE) national scientific user facility and is the centerpiece of the DOE commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems.

  10. Simulation and modeling of homogeneous, compressed turbulence

    NASA Technical Reports Server (NTRS)

    Wu, C. T.; Ferziger, J. H.; Chapman, D. R.

    1985-01-01

    Low Reynolds number homogeneous turbulence undergoing low Mach number isotropic and one-dimensional compression was simulated by numerically solving the Navier-Stokes equations. The numerical simulations were performed on a CYBER 205 computer using a 64 x 64 x 64 mesh. A spectral method was used for spatial differencing and the second-order Runge-Kutta method for time advancement. A variety of statistical information was extracted from the computed flow fields. These include three-dimensional energy and dissipation spectra, two-point velocity correlations, one-dimensional energy spectra, turbulent kinetic energy and its dissipation rate, integral length scales, Taylor microscales, and Kolmogorov length scale. Results from the simulated flow fields were used to test one-point closure, two-equation models. A new one-point-closure, three-equation turbulence model which accounts for the effect of compression is proposed. The new model accurately calculates four types of flows (isotropic decay, isotropic compression, one-dimensional compression, and axisymmetric expansion flows) for a wide range of strain rates.

  11. Progress in Modeling and Simulation of Batteries

    SciTech Connect

    Turner, John A

    2016-01-01

    Modeling and simulation of batteries, in conjunction with theory and experiment, are important research tools that offer opportunities for advancement of technologies that are critical to electric motors. The development of data from the application of these tools can provide the basis for managerial and technical decision-making. Together, these will continue to transform batteries for electric vehicles. This collection of nine papers presents the modeling and simulation of batteries and the continuing contribution being made to this impressive progress, including topics that cover: * Thermal behavior and characteristics * Battery management system design and analysis * Moderately high-fidelity 3D capabilities * Optimization Techniques and Durability As electric vehicles continue to gain interest from manufacturers and consumers alike, improvements in economy and affordability, as well as adoption of alternative fuel sources to meet government mandates are driving battery research and development. Progress in modeling and simulation will continue to contribute to battery improvements that deliver increased power, energy storage, and durability to further enhance the appeal of electric vehicles.

  12. Streptococcus mutans, Caries and Simulation Models

    PubMed Central

    Forssten, Sofia D.; Björklund, Marika; Ouwehand, Arthur C.

    2010-01-01

    Dental caries and dental plaque are among the most common diseases worldwide, and are caused by a mixture of microorganisms and food debris. Specific types of acid-producing bacteria, especially Streptococcus mutans, colonize the dental surface and cause damage to the hard tooth structure in the presence of fermentable carbohydrates e.g., sucrose and fructose. This paper reviews the link between S. mutans and caries, as well as different simulation models that are available for studying caries. These models offer a valuable approach to study cariogenicity of different substrates as well as colonization of S. mutans. PMID:22254021

  13. Computer Models Simulate Fine Particle Dispersion

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Through a NASA Seed Fund partnership with DEM Solutions Inc., of Lebanon, New Hampshire, scientists at Kennedy Space Center refined existing software to study the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces. The software, EDEM, allows users to import particles and obtain accurate representations of their shapes for modeling purposes, such as simulating bulk solids behavior, and was enhanced to be able to more accurately model fine, abrasive, cohesive particles. These new EDEM capabilities can be applied in many industries unrelated to space exploration and have been adopted by several prominent U.S. companies, including John Deere, Pfizer, and Procter & Gamble.

  14. Simulated lights for an airfield model

    NASA Technical Reports Server (NTRS)

    Gdovin, David P. (Inventor); Lusk, Frank J. (Inventor)

    1982-01-01

    A light at an aircraft landing site is simulated on a model board by the protruding output end of a precision cut optical fiber. The fiber is secured within a counterbore of a counterbored hole in the model board. The length of the precision cut fiber and the depth of the counterbore are closely controlled to ensure that the output end of the fiber protrudes a desired distance. The input end of the precision cut fiber is optically coupled to a collimated light source by a second optical fiber extending through the smaller diameter bore of the counterbored hole.

  15. Consolidation modelling for thermoplastic composites forming simulation

    NASA Astrophysics Data System (ADS)

    Xiong, H.; Rusanov, A.; Hamila, N.; Boisse, P.

    2016-10-01

    Pre-impregnated thermoplastic composites are widely used in the aerospace industry for their excellent mechanical properties, Thermoforming thermoplastic prepregs is a fast manufacturing process, the automotive industry has shown increasing interest in this manufacturing processes, in which the reconsolidation is an essential stage. The model of intimate contact is investigated as the consolidation model, compression experiments have been launched to identify the material parameters, several numerical tests show the influents of the temperature and pressure applied during processing. Finally, a new solid-shell prismatic element has been presented for the simulation of consolidation step in the thermoplastic composites forming process.

  16. Nonlinear friction model for servo press simulation

    NASA Astrophysics Data System (ADS)

    Ma, Ninshu; Sugitomo, Nobuhiko; Kyuno, Takunori; Tamura, Shintaro; Naka, Tetsuo

    2013-12-01

    The friction coefficient was measured under an idealized condition for a pulse servo motion. The measured friction coefficient and its changing with both sliding distance and a pulse motion showed that the friction resistance can be reduced due to the re-lubrication during unloading process of the pulse servo motion. Based on the measured friction coefficient and its changes with sliding distance and re-lubrication of oil, a nonlinear friction model was developed. Using the newly developed the nonlinear friction model, a deep draw simulation was performed and the formability was evaluated. The results were compared with experimental ones and the effectiveness was verified.

  17. Computational Modeling and Simulation of Genital Tubercle ...

    EPA Pesticide Factsheets

    Hypospadias is a developmental defect of urethral tube closure that has a complex etiology. Here, we describe a multicellular agent-based model of genital tubercle development that simulates urethrogenesis from the urethral plate stage to urethral tube closure in differentiating male embryos. The model, constructed in CompuCell3D, implemented spatially dynamic signals from SHH, FGF10, and androgen signaling pathways. These signals modulated stochastic cell behaviors, such as differential adhesion, cell motility, proliferation, and apoptosis. Urethral tube closure was an emergent property of the model that was quantitatively dependent on SHH and FGF10 induced effects on mesenchymal proliferation and endodermal apoptosis, ultimately linked to androgen signaling. In the absence of androgenization, simulated genital tubercle development defaulted to the female condition. Intermediate phenotypes associated with partial androgen deficiency resulted in incomplete closure. Using this computer model, complex relationships between urethral tube closure defects and disruption of underlying signaling pathways could be probed theoretically in multiplex disturbance scenarios and modeled into probabilistic predictions for individual risk for hypospadias and potentially other developmental defects of the male genital tubercle. We identify the minimal molecular network that determines the outcome of male genital tubercle development in mice.

  18. Biomedical Simulation Models of Human Auditory Processes

    NASA Technical Reports Server (NTRS)

    Bicak, Mehmet M. A.

    2012-01-01

    Detailed acoustic engineering models that explore noise propagation mechanisms associated with noise attenuation and transmission paths created when using hearing protectors such as earplugs and headsets in high noise environments. Biomedical finite element (FE) models are developed based on volume Computed Tomography scan data which provides explicit external ear, ear canal, middle ear ossicular bones and cochlea geometry. Results from these studies have enabled a greater understanding of hearing protector to flesh dynamics as well as prioritizing noise propagation mechanisms. Prioritization of noise mechanisms can form an essential framework for exploration of new design principles and methods in both earplug and earcup applications. These models are currently being used in development of a novel hearing protection evaluation system that can provide experimentally correlated psychoacoustic noise attenuation. Moreover, these FE models can be used to simulate the effects of blast related impulse noise on human auditory mechanisms and brain tissue.

  19. Integrating Visualizations into Modeling NEST Simulations

    PubMed Central

    Nowke, Christian; Zielasko, Daniel; Weyers, Benjamin; Peyser, Alexander; Hentschel, Bernd; Kuhlen, Torsten W.

    2015-01-01

    Modeling large-scale spiking neural networks showing realistic biological behavior in their dynamics is a complex and tedious task. Since these networks consist of millions of interconnected neurons, their simulation produces an immense amount of data. In recent years it has become possible to simulate even larger networks. However, solutions to assist researchers in understanding the simulation's complex emergent behavior by means of visualization are still lacking. While developing tools to partially fill this gap, we encountered the challenge to integrate these tools easily into the neuroscientists' daily workflow. To understand what makes this so challenging, we looked into the workflows of our collaborators and analyzed how they use the visualizations to solve their daily problems. We identified two major issues: first, the analysis process can rapidly change focus which requires to switch the visualization tool that assists in the current problem domain. Second, because of the heterogeneous data that results from simulations, researchers want to relate data to investigate these effectively. Since a monolithic application model, processing and visualizing all data modalities and reflecting all combinations of possible workflows in a holistic way, is most likely impossible to develop and to maintain, a software architecture that offers specialized visualization tools that run simultaneously and can be linked together to reflect the current workflow, is a more feasible approach. To this end, we have developed a software architecture that allows neuroscientists to integrate visualization tools more closely into the modeling tasks. In addition, it forms the basis for semantic linking of different visualizations to reflect the current workflow. In this paper, we present this architecture and substantiate the usefulness of our approach by common use cases we encountered in our collaborative work. PMID:26733860

  20. Atomistic modeling and simulation of nanopolycrystalline solids

    NASA Astrophysics Data System (ADS)

    Yang, Zidong

    In the past decades, nanostructured materials have opened new and fascinating avenues for research. Nanopolycrystalline solids, which consist of nano-sized crystalline grains and significant volume fractions of amorphous grain boundaries, are believed to have substantially different response to the thermal-mechanical-electric-magnetic loads, as compared to the response of single-crystalline materials. Nanopolycrystalline materials are expected to play a key role in the next generation of smart materials. This research presents a framework (1) to generate full atomistic models, (2) to perform non-equilibrium molecular dynamics simulations, and (3) to study multi-physics phenomena of nanopolycrystalline solids. This work starts the physical model and mathematical representation with the framework of molecular dynamics. In addition to the latest theories and techniques of molecular dynamics simulations, this work implemented principle of objectivity and incorporates multi-physics features. Further, a database of empirical interatomic potentials is established and the combination scheme for potentials is revisited, which enables investigation of a broad spectrum of chemical elements (as in periodic table) and compounds (such as rocksalt, perovskite, wurtzite, diamond, etc.). The configurational model of nanopolycrystalline solids consists of two spatial components: (1) crystalline grains, which can be obtained through crystal structure optimization, and (2) amorphous grain boundaries, which can be obtained through amorphization process. Therefore, multi-grain multi-phase nanopolycrystalline material system can be constructed by partitioning the space for grains, followed by filling the inter-grain space with amorphous grain boundaries. Computational simulations are performed on several representative crystalline materials and their mixture, such as rocksalt, perovskite and diamond. Problems of relaxation, mechanical loading, thermal stability, heat conduction

  1. Desktop Modeling and Simulation: Parsimonious, yet Effective Discrete-Event Simulation Analysis

    NASA Technical Reports Server (NTRS)

    Bradley, James R.

    2012-01-01

    This paper evaluates how quickly students can be trained to construct useful discrete-event simulation models using Excel The typical supply chain used by many large national retailers is described, and an Excel-based simulation model is constructed of it The set of programming and simulation skills required for development of that model are then determined we conclude that six hours of training are required to teach the skills to MBA students . The simulation presented here contains all fundamental functionallty of a simulation model, and so our result holds for any discrete-event simulation model. We argue therefore that Industry workers with the same technical skill set as students having completed one year in an MBA program can be quickly trained to construct simulation models. This result gives credence to the efficacy of Desktop Modeling and Simulation whereby simulation analyses can be quickly developed, run, and analyzed with widely available software, namely Excel.

  2. [Modeling and Simulation of Spectral Polarimetric BRDF].

    PubMed

    Ling, Jin-jiang; Li, Gang; Zhang, Ren-bin; Tang, Qian; Ye, Qiu

    2016-01-01

    Under the conditions of the polarized light, The reflective surface of the object is affected by many factors, refractive index, surface roughness, and so the angle of incidence. For the rough surface in the different wavelengths of light exhibit different reflection characteristics of polarization, a spectral polarimetric BRDF based on Kirchhof theory is proposee. The spectral model of complex refraction index is combined with refraction index and extinction coefficient spectral model which were got by using the known complex refraction index at different value. Then get the spectral model of surface roughness derived from the classical surface roughness measuring method combined with the Fresnel reflection function. Take the spectral model of refraction index and roughness into the BRDF model, then the spectral polarimetirc BRDF model is proposed. Compare the simulation results of the refractive index varies with wavelength, roughness is constant, the refraction index and roughness both vary with wavelength and origin model with other papers, it shows that, the spectral polarimetric BRDF model can show the polarization characteristics of the surface accurately, and can provide a reliable basis for the application of polarization remote sensing, and other aspects of the classification of substances.

  3. Best Practices for Crash Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin L.; Jackson, Karen E.

    2002-01-01

    Aviation safety can be greatly enhanced by the expeditious use of computer simulations of crash impact. Unlike automotive impact testing, which is now routine, experimental crash tests of even small aircraft are expensive and complex due to the high cost of the aircraft and the myriad of crash impact conditions that must be considered. Ultimately, the goal is to utilize full-scale crash simulations of aircraft for design evaluation and certification. The objective of this publication is to describe "best practices" for modeling aircraft impact using explicit nonlinear dynamic finite element codes such as LS-DYNA, DYNA3D, and MSC.Dytran. Although "best practices" is somewhat relative, it is hoped that the authors' experience will help others to avoid some of the common pitfalls in modeling that are not documented in one single publication. In addition, a discussion of experimental data analysis, digital filtering, and test-analysis correlation is provided. Finally, some examples of aircraft crash simulations are described in several appendices following the main report.

  4. Systematic simulations of modified gravity: chameleon models

    SciTech Connect

    Brax, Philippe; Li, Baojiu; Winther, Hans A.; Zhao, Gong-Bo E-mail: a.c.davis@damtp.cam.ac.uk E-mail: h.a.winther@astro.uio.no

    2013-04-01

    In this work we systematically study the linear and nonlinear structure formation in chameleon theories of modified gravity, using a generic parameterisation which describes a large class of models using only 4 parameters. For this we have modified the N-body simulation code ecosmog to perform a total of 65 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a significant portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM paradigm cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc{sup −1}, since the latter incorrectly assumes that the modification of gravity depends only on the background matter density. Our results show that the chameleon screening mechanism is significantly more efficient than other mechanisms such as the dilaton and symmetron, especially in high-density regions and at early times, and can serve as a guidance to determine the parts of the chameleon parameter space which are cosmologically interesting and thus merit further studies in the future.

  5. Application of simulation models for the optimization of business processes

    NASA Astrophysics Data System (ADS)

    Jašek, Roman; Sedláček, Michal; Chramcov, Bronislav; Dvořák, Jiří

    2016-06-01

    The paper deals with the applications of modeling and simulation tools in the optimization of business processes, especially in solving an optimization of signal flow in security company. As a modeling tool was selected Simul8 software that is used to process modeling based on discrete event simulation and which enables the creation of a visual model of production and distribution processes.

  6. Simulation Assisted Risk Assessment: Blast Overpressure Modeling

    NASA Technical Reports Server (NTRS)

    Lawrence, Scott L.; Gee, Ken; Mathias, Donovan; Olsen, Michael

    2006-01-01

    A probabilistic risk assessment (PRA) approach has been developed and applied to the risk analysis of capsule abort during ascent. The PRA is used to assist in the identification of modeling and simulation applications that can significantly impact the understanding of crew risk during this potentially dangerous maneuver. The PRA approach is also being used to identify the appropriate level of fidelity for the modeling of those critical failure modes. The Apollo launch escape system (LES) was chosen as a test problem for application of this approach. Failure modes that have been modeled and/or simulated to date include explosive overpressure-based failure, explosive fragment-based failure, land landing failures (range limits exceeded either near launch or Mode III trajectories ending on the African continent), capsule-booster re-contact during separation, and failure due to plume-induced instability. These failure modes have been investigated using analysis tools in a variety of technical disciplines at various levels of fidelity. The current paper focuses on the development and application of a blast overpressure model for the prediction of structural failure due to overpressure, including the application of high-fidelity analysis to predict near-field and headwinds effects.

  7. A Simple Memristor Model for Circuit Simulations

    NASA Astrophysics Data System (ADS)

    Fullerton, Farrah-Amoy; Joe, Aaleyah; Gergel-Hackett, Nadine; Department of Chemistry; Physics Team

    This work describes the development of a model for the memristor, a novel nanoelectronic technology. The model was designed to replicate the real-world electrical characteristics of previously fabricated memristor devices, but was constructed with basic circuit elements using a free widely available circuit simulator, LT Spice. The modeled memrsistors were then used to construct a circuit that performs material implication. Material implication is a digital logic that can be used to perform all of the same basic functions as traditional CMOS gates, but with fewer nanoelectronic devices. This memristor-based digital logic could enable memristors' use in new paradigms of computer architecture with advantages in size, speed, and power over traditional computing circuits. Additionally, the ability to model the real-world electrical characteristics of memristors in a free circuit simulator using its standard library of elements could enable not only the development of memristor material implication, but also the development of a virtually unlimited array of other memristor-based circuits.

  8. Closed loop models for analyzing the effects of simulator characteristics. [digital simulation of human operators

    NASA Technical Reports Server (NTRS)

    Baron, S.; Muralidharan, R.; Kleinman, D. L.

    1978-01-01

    The optimal control model of the human operator is used to develop closed loop models for analyzing the effects of (digital) simulator characteristics on predicted performance and/or workload. Two approaches are considered: the first utilizes a continuous approximation to the discrete simulation in conjunction with the standard optimal control model; the second involves a more exact discrete description of the simulator in a closed loop multirate simulation in which the optimal control model simulates the pilot. Both models predict that simulator characteristics can have significant effects on performance and workload.

  9. Staring array sensor model for simulation implementation

    NASA Astrophysics Data System (ADS)

    Willers, Cornelius J.; Willers, Maria S.

    2016-02-01

    A comprehensive model for staring array simulation is described. The model covers all effects from photon signal generation through to detection and processing in the staring array sensor. The model follows the signal flow from photon generation, through a staring focal plane array (FPA) from the detector, through several conversions in the read out integrated circuit (ROIC) and finally conversion to a digital signal. Spatial nonuniformity modeling for photoresponse, dark current generation and source follower offset is included. The list of noise sources includes: photon noise, quantum conversion uncertainty, dark noise, kTC noise, source follower noise and quantization noise. Several components with (simplified) nonlinear responses are also modeled: sense node capacitance variation with charge, source follower nonlinearity and nonlinearity in the digital conversion. The code implementations take images as input, applying the various processes independently on individual pixels (e.g., shot noise) or on complete images (e.g., spatial nonuniformity). Some noise sources vary temporally across frames (shot, thermal, kTC) while other noise sources are fixed across frames (fixed pattern noises). The application of the model is demonstrated by tracing the signal path from source to sensor output, with intermediate results along the path. The model is implemented in Python (as part of the pyradi open source computational radiometry module) and in a C++ image simulation. The purpose with this work is to predict what the performance of a given sensor will be in terms of image appearance, given the devices specifications and key design parameters. The execution of this work lead to the important recommendation that nonuniformity correction for infrared sensors should be performed at well fill levels corresponding to the minimum and maximum in the scene, not to fixed percentage levels in the charge well. The objective with this work is to provide a `generic' model that can be

  10. Volumetric modeling in laser BPH therapy simulation.

    PubMed

    Zhang, Nan; Zhou, Xiangmin; Shen, Yunhe; Sweet, Robert

    2010-01-01

    In this paper, we introduce a novel application of volume modeling techniques on laser Benign Prostatic Hyperplasia (BPH) therapy simulation. The core technique in our system is an algorithm for simulating the tissue vaporization process by laser heating. Different from classical volume CSG operations, our technique takes experimental data as the guidance to determine the vaporization amount so that only a specified amount of tissue is vaporized in each time. Our algorithm uses a predictor-corrector strategy. First, we apply the classical CSG algorithm on a tetrahedral grid based distance field to estimate the vaporized tissue amount. Then, a volume-correction phase is applied on the distance field. To improve the performance, we further propose optimization approaches for efficient implementation.

  11. Models for naturally fractured, carbonate reservoir simulations

    SciTech Connect

    Tuncay, K.; Park, A.; Ozkan, G.; Zhan, X.; Ortoleva, P.; Hoak, T.; Sundberg, K.

    1998-12-31

    This report outlines the need for new tools for the simulation of fractured carbonate reservoirs. Several problems are identified that call for the development of new reservoir simulation physical models and numerical techniques. These include: karst and vuggy media wherein Darcy`s and traditional multi-phase flow laws do not apply; the need for predicting the preproduction state of fracturing and stress so that the later response of effective stress-dependent reservoirs can be predicted; and methods for predicting the fracturing and collapse of vuggy and karst reservoirs in response to draw-down pressure created during production. Specific research directions for addressing each problem are outlined and preliminary results are noted.

  12. Implications of Simulation Conceptual Model Development for Simulation Management and Uncertainty Assessment

    NASA Technical Reports Server (NTRS)

    Pace, Dale K.

    2000-01-01

    A simulation conceptual model is a simulation developers way of translating modeling requirements (i. e., what is to be represented by the simulation or its modification) into a detailed design framework (i. e., how it is to be done), from which the software, hardware, networks (in the case of distributed simulation), and systems/equipment that will make up the simulation can be built or modified. A conceptual model is the collection of information which describes a simulation developers concept about the simulation and its pieces. That information consists of assumptions, algorithms, characteristics, relationships, and data. Taken together, these describe how the simulation developer understands what is to be represented by the simulation (entities, actions, tasks, processes, interactions, etc.) and how that representation will satisfy the requirements to which the simulation responds. Thus the conceptual model is the basis for judgment about simulation fidelity and validity for any condition that is not specifically tested. The more perspicuous and precise the conceptual model, the more likely it is that the simulation development will both fully satisfy requirements and allow demonstration that the requirements are satisfied (i. e., validation). Methods used in simulation conceptual model development have significant implications for simulation management and for assessment of simulation uncertainty. This paper suggests how to develop and document a simulation conceptual model so that the simulation fidelity and validity can be most effectively determined. These ideas for conceptual model development apply to all simulation varieties. The paper relates these ideas to uncertainty assessments as they relate to simulation fidelity and validity. The paper also explores implications for simulation management from conceptual model development methods, especially relative to reuse of simulation components.

  13. An Investigation of System Identification Techniques for Simulation Model Abstraction

    DTIC Science & Technology

    2000-02-01

    This report summarizes research into the application of system identification techniques to simulation model abstraction. System identification produces...34Mission Simulation," a simulation of a squadron of aircraft performing battlefield air interdiction. The system identification techniques were...simplified mathematical models that approximate the dynamic behaviors of the underlying stochastic simulations. Four state-space system

  14. Modeling and Simulation. III. Simulation of a Model for Development of Visual Cortical Specificity.

    DTIC Science & Technology

    1986-12-15

    of parameter values. Experiment, model, and simulation 5’ The simulations we consider mimic, in form, classic deprivation experiments. Kittens are...second paper of the series (ref. 8) reviews the results of numerous experiments on the neuronal development of kitten visual cortex. We have...restricted to a very limited range of oriented contours (see citations in ref. 8). Kittens were raised, for example, viewing only horizontal or only vertical

  15. Modeling galactic chemical evolution in cosmological simulations

    NASA Astrophysics Data System (ADS)

    Peruta, Carolyn Cynthia

    The most fundamental challenges to models of galactic chemical evolution (GCE) are uncertainties in the basic inputs, including the properties of the stellar initial mass function (IMF), stellar nucleosynthetic yields, and the rate of return of mass and energy to the interstellar and intergalactic medium by Type Ia and II supernovae and stellar winds. In this dissertation, we provide a critical examination of widely available stellar nucleosynthetic yield data, with an eye toward modeling GCE in the broad scope of cosmological hydrodynamical simulations. We examine the implications of uncertain inputs for the Galactic stellar IMF, and nucleosynthetic yields from stellar-evolution calculations, on our ability to ask detailed questions regarding the observed Galactic chemical-abundance patterns. We find a marked need for stellar feedback data from stars of initial mass 8 to 12 Msun and above 40 M sun, and for initial stellar metallicities above and below solar, Z sun=0.02. We find the largest discrepancies amongst nucleosynthetic yield calculations are due to various groups' treatment of hot bottom burning, formation of the 13C pocket in asymptotic giant-branch (AGB) stars, and details of mass loss, rotation, and convection in all stars. Our model of GCE is used to post-process simulations to explore in greater detail the nucleosynthetic evolution of the stellar populations and interstellar/intergalactic medium, and to compare directly to the chemical abundances of the Milky Way stellar halo and dwarf spheroidal galaxy stellar populations.

  16. Simulation Model of Mobile Detection Systems

    SciTech Connect

    Edmunds, T; Faissol, D; Yao, Y

    2009-01-27

    In this paper, we consider a mobile source that we attempt to detect with man-portable, vehicle-mounted or boat-mounted radiation detectors. The source is assumed to transit an area populated with these mobile detectors, and the objective is to detect the source before it reaches a perimeter. We describe a simulation model developed to estimate the probability that one of the mobile detectors will come in to close proximity of the moving source and detect it. We illustrate with a maritime simulation example. Our simulation takes place in a 10 km by 5 km rectangular bay patrolled by boats equipped with 2-inch x 4-inch x 16-inch NaI detectors. Boats to be inspected enter the bay and randomly proceed to one of seven harbors on the shore. A source-bearing boat enters the mouth of the bay and proceeds to a pier on the opposite side. We wish to determine the probability that the source is detected and its range from target when detected. Patrol boats select the nearest in-bound boat for inspection and initiate an intercept course. Once within an operational range for the detection system, a detection algorithm is started. If the patrol boat confirms the source is not present, it selects the next nearest boat for inspection. Each run of the simulation ends either when a patrol successfully detects a source or when the source reaches its target. Several statistical detection algorithms have been implemented in the simulation model. First, a simple k-sigma algorithm, which alarms with the counts in a time window exceeds the mean background plus k times the standard deviation of background, is available to the user. The time window used is optimized with respect to the signal-to-background ratio for that range and relative speed. Second, a sequential probability ratio test [Wald 1947] is available, and configured in this simulation with a target false positive probability of 0.001 and false negative probability of 0.1. This test is utilized when the mobile detector maintains

  17. Multi-formalism modelling and simulation: application to cardiac modelling

    PubMed Central

    Defontaine, Antoine; Hernández, Alfredo; Carrault, Guy

    2004-01-01

    Cardiovascular modelling has been a major research subject for the last decades. Different cardiac models have been developed at a cellular level as well as at the whole organ level. Most of these models are defined by a comprehensive cellular modelling using continuous formalisms or by a tissue-level modelling often based on discrete formalisms. Nevertheless, both views still suffer from difficulties that reduce their clinical applications: the first approach requires heavy computational resources while the second one is not able to reproduce certain pathologies. This paper presents an original methodology trying to gather advantages from both approaches, by means of an hybrid model mixing discrete and continuous formalisms. This method has been applied to define a hybrid model of cardiac action potential propagation on a 2D grid of endocardial cells, combining cellular automata and a set of cells defined by the Beeler Reuter model. For simulations under physiologic and ischemic conditions, results show that the action potential propagation as well as electrogram reconstructions are consistent with clinical diagnosis. Finally, the interest of the proposed approach is discussed within the frame of cardiac modelling and simulation. PMID:15520534

  18. Coarse-grained models for biological simulations

    NASA Astrophysics Data System (ADS)

    Wu, Zhe; Cui, Qiang; Yethiraj, Arun

    2011-03-01

    The large timescales and length-scales of interest in biophysics preclude atomistic study of many systems and processes. One appealing approach is to use coarse-grained (CG) models where several atoms are grouped into a single CG site. In this work we describe a new CG force field for lipids, surfactants, and amino acids. The topology of CG sites is the same as in the MARTINI force field, but the new model is compatible with a recently developed CG electrostatic water (Big Multiple Water, BMW) model. The model not only gives correct structural, elastic properties and phase behavior for lipid and surfactants, but also reproduces electrostatic properties at water-membrane interface that agree with experiment and atomistic simulations, including the potential of mean force for charged amino acid residuals at membrane. Consequently, the model predicts stable attachment of cationic peptides (i.e., poly-Arg) on lipid bilayer surface, which is not shown in previous models with non-electrostatic water.

  19. Petroleum reservoir data for testing simulation models

    SciTech Connect

    Lloyd, J.M.; Harrison, W.

    1980-09-01

    This report consists of reservoir pressure and production data for 25 petroleum reservoirs. Included are 5 data sets for single-phase (liquid) reservoirs, 1 data set for a single-phase (liquid) reservoir with pressure maintenance, 13 data sets for two-phase (liquid/gas) reservoirs and 6 for two-phase reservoirs with pressure maintenance. Also given are ancillary data for each reservoir that could be of value in the development and validation of simulation models. A bibliography is included that lists the publications from which the data were obtained.

  20. Modeling and simulation technology readiness levels.

    SciTech Connect

    Clay, Robert L.; Shneider, Max S.; Marburger, S. J.; Trucano, Timothy Guy

    2006-01-01

    This report summarizes the results of an effort to establish a framework for assigning and communicating technology readiness levels (TRLs) for the modeling and simulation (ModSim) capabilities at Sandia National Laboratories. This effort was undertaken as a special assignment for the Weapon Simulation and Computing (WSC) program office led by Art Hale, and lasted from January to September 2006. This report summarizes the results, conclusions, and recommendations, and is intended to help guide the program office in their decisions about the future direction of this work. The work was broken out into several distinct phases, starting with establishing the scope and definition of the assignment. These are characterized in a set of key assertions provided in the body of this report. Fundamentally, the assignment involved establishing an intellectual framework for TRL assignments to Sandia's modeling and simulation capabilities, including the development and testing of a process to conduct the assignments. To that end, we proposed a methodology for both assigning and understanding the TRLs, and outlined some of the restrictions that need to be placed on this process and the expected use of the result. One of the first assumptions we overturned was the notion of a ''static'' TRL--rather we concluded that problem context was essential in any TRL assignment, and that leads to dynamic results (i.e., a ModSim tool's readiness level depends on how it is used, and by whom). While we leveraged the classic TRL results from NASA, DoD, and Sandia's NW program, we came up with a substantially revised version of the TRL definitions, maintaining consistency with the classic level definitions and the Predictive Capability Maturity Model (PCMM) approach. In fact, we substantially leveraged the foundation the PCMM team provided, and augmented that as needed. Given the modeling and simulation TRL definitions and our proposed assignment methodology, we conducted four ''field trials'' to

  1. Modelling and simulations of controlled release fertilizer

    NASA Astrophysics Data System (ADS)

    Irfan, Sayed Ameenuddin; Razali, Radzuan; Shaari, Ku Zilati Ku; Mansor, Nurlidia

    2016-11-01

    The recent advancement in controlled release fertilizer has provided an alternative solution to the conventional urea, controlled release fertilizer has a good plant nutrient uptake they are environment friendly. To have an optimum plant intake of nutrients from controlled release fertilizer it is very essential to understand the release characteristics. A mathematical model is developed to predict the release characteristics from polymer coated granule. Numerical simulations are performed by varying the parameters radius of granule, soil water content and soil porosity to study their effect on fertilizer release. Understanding these parameters helps in the better design and improve the efficiency of controlled release fertilizer.

  2. The simulation model of planar electrochemical transducer

    NASA Astrophysics Data System (ADS)

    Zhevnenko, D. A.; Vergeles, S. S.; Krishtop, T. V.; Tereshonok, D. V.; Gornev, E. S.; Krishtop, V. G.

    2016-12-01

    Planar electrochemical systems are very perspective to build modern motion and pressure sensors. Planar microelectronic technology is successfully used for electrochemical transducer of motion parameters. These systems are characterized by an exceptionally high sensitivity towards mechanic exposure due to high rate of conversion of the mechanic signal to electric current. In this work, we have developed a mathematical model of this planar electrochemical system, which detects the mechanical signals. We simulate the processes of mass and charge transfer in planar electrochemical transducer and calculated its transfer function with different geometrical parameters of the system.

  3. Distributed Slip Model for Simulating Virtual Earthquakes

    NASA Astrophysics Data System (ADS)

    Shani-Kadmiel, S.; Tsesarsky, M.; Gvirtzman, Z.

    2014-12-01

    We develop a physics based, generic finite fault source, which we call the Distributed Slip Model (DSM) for simulating large virtual earthquakes. This task is a necessary step towards ground motion prediction in earthquake-prone areas with limited instrumental coverage. A reliable ground motion prediction based on virtual earthquakes must account for site, path, and source effects. Assessment of site effect mainly depends on near-surface material properties which are relatively well constrained, using geotechnical site data and borehole measurements. Assessment of path effect depends on the deeper geological structure, which is also typically known to an acceptable resolution. Contrarily to these two effects, which remain constant for a given area of interest, the earthquake rupture process and geometry varies from one earthquake to the other. In this study we focus on a finite fault source representation which is both generic and physics-based, for simulating large earthquakes where limited knowledge is available. Thirteen geometric and kinematic parameters are used to describe the smooth "pseudo-Gaussian" slip distribution, such that slip decays from a point of peak slip within an elliptical rupture patch to zero at the borders of the patch. Radiation pattern and spectral charectaristics of our DSM are compared to those of commonly used finite fault models, i.e., the classical Haskell's Model (HM) and the modified HM with Radial Rupture Propagation (HM-RRP) and the Point Source Model (PSM). Ground motion prediction based on our DSM benefits from the symmetry of the PSM and the directivity of the HM while overcoming inadequacy for modeling large earthquakes of the former and the non-physical uniform slip of the latter.

  4. Modeling, Simulation, and Forecasting of Subseasonal Variability

    NASA Technical Reports Server (NTRS)

    Waliser, Duane; Schubert, Siegfried; Kumar, Arun; Weickmann, Klaus; Dole, Randall

    2003-01-01

    A planning workshop on "Modeling, Simulation and Forecasting of Subseasonal Variability" was held in June 2003. This workshop was the first of a number of meetings planned to follow the NASA-sponsored workshop entitled "Prospects For Improved Forecasts Of Weather And Short-Term Climate Variability On Sub-Seasonal Time Scales" that was held April 2002. The 2002 workshop highlighted a number of key sources of unrealized predictability on subseasonal time scales including tropical heating, soil wetness, the Madden Julian Oscillation (MJO) [a.k.a Intraseasonal Oscillation (ISO)], the Arctic Oscillation (AO) and the Pacific/North American (PNA) pattern. The overarching objective of the 2003 follow-up workshop was to proceed with a number of recommendations made from the 2002 workshop, as well as to set an agenda and collate efforts in the areas of modeling, simulation and forecasting intraseasonal and short-term climate variability. More specifically, the aims of the 2003 workshop were to: 1) develop a baseline of the "state of the art" in subseasonal prediction capabilities, 2) implement a program to carry out experimental subseasonal forecasts, and 3) develop strategies for tapping the above sources of predictability by focusing research, model development, and the development/acquisition of new observations on the subseasonal problem. The workshop was held over two days and was attended by over 80 scientists, modelers, forecasters and agency personnel. The agenda of the workshop focused on issues related to the MJO and tropicalextratropical interactions as they relate to the subseasonal simulation and prediction problem. This included the development of plans for a coordinated set of GCM hindcast experiments to assess current model subseasonal prediction capabilities and shortcomings, an emphasis on developing a strategy to rectify shortcomings associated with tropical intraseasonal variability, namely diabatic processes, and continuing the implementation of an

  5. Orion Landing Simulation Eight Soil Model Comparison

    NASA Technical Reports Server (NTRS)

    Mark, Stephen D.

    2009-01-01

    LS-DYNA finite element simulations of a rigid Orion Crew Module (CM) were used to investigate the CM impact behavior on eight different soil models. Ten different landing conditions, characterized by the combination of CM vertical and horizontal velocity, hang angle, and roll angle were simulated on the eight different soils. The CM center of gravity accelerations, pitch angle, kinetic energy, and soil contact forces were the outputs of interest. The simulation results are presented, with comparisons of the CM behavior on the different soils. The soils analyzed in this study can be roughly categorized as soft, medium, or hard, according to the CM accelerations that occur when landing on them. The soft group is comprised of the Carson Sink Wet soil and the Kennedy Space Center (KSC) Low Density Dry Sand. The medium group includes Carson Sink Dry, the KSC High Density In-Situ Moisture Sand and High Density Flooded Sand, and Cuddeback B. The hard soils are Cuddeback A and the Gantry Unwashed Sand. The softer soils were found to produce lower peak accelerations, have more stable pitch behavior, and to be less sensitive to the landing conditions. This investigation found that the Cuddeback A soil produced the highest peak accelerations and worst stability conditions, and that the best landing performance was achieved on the KSC Low Density Dry Sand.

  6. Simulation model for port shunting yards

    NASA Astrophysics Data System (ADS)

    Rusca, A.; Popa, M.; Rosca, E.; Rosca, M.; Dragu, V.; Rusca, F.

    2016-08-01

    Sea ports are important nodes in the supply chain, joining two high capacity transport modes: rail and maritime transport. The huge cargo flows transiting port requires high capacity construction and installation such as berths, large capacity cranes, respectively shunting yards. However, the port shunting yards specificity raises several problems such as: limited access since these are terminus stations for rail network, the in-output of large transit flows of cargo relatively to the scarcity of the departure/arrival of a ship, as well as limited land availability for implementing solutions to serve these flows. It is necessary to identify technological solutions that lead to an answer to these problems. The paper proposed a simulation model developed with ARENA computer simulation software suitable for shunting yards which serve sea ports with access to the rail network. Are investigates the principal aspects of shunting yards and adequate measures to increase their transit capacity. The operation capacity for shunting yards sub-system is assessed taking in consideration the required operating standards and the measure of performance (e.g. waiting time for freight wagons, number of railway line in station, storage area, etc.) of the railway station are computed. The conclusion and results, drawn from simulation, help transports and logistics specialists to test the proposals for improving the port management.

  7. Beyond modeling: all-atom olfactory receptor model simulations.

    PubMed

    Lai, Peter C; Crasto, Chiquito J

    2012-01-01

    Olfactory receptors (ORs) are a type of GTP-binding protein-coupled receptor (GPCR). These receptors are responsible for mediating the sense of smell through their interaction with odor ligands. OR-odorant interactions marks the first step in the process that leads to olfaction. Computational studies on model OR structures can generate focused and novel hypotheses for further bench investigation by providing a view of these interactions at the molecular level beyond inferences that are drawn merely from static docking. Here we have shown the specific advantages of simulating the dynamic environment associated with OR-odorant interactions. We present a rigorous protocol which ranges from the creation of a computationally derived model of an olfactory receptor to simulating the interactions between an OR and an odorant molecule. Given the ubiquitous occurrence of GPCRs in the membranes of cells, we anticipate that our OR-developed methodology will serve as a model for the computational structural biology of all GPCRs.

  8. VISION: Verifiable Fuel Cycle Simulation Model

    SciTech Connect

    Jacob J. Jacobson; Abdellatif M. Yacout; Gretchen E. Matthern; Steven J. Piet; David E. Shropshire

    2009-04-01

    The nuclear fuel cycle is a very complex system that includes considerable dynamic complexity as well as detail complexity. In the nuclear power realm, there are experts and considerable research and development in nuclear fuel development, separations technology, reactor physics and waste management. What is lacking is an overall understanding of the entire nuclear fuel cycle and how the deployment of new fuel cycle technologies affects the overall performance of the fuel cycle. The Advanced Fuel Cycle Initiative’s systems analysis group is developing a dynamic simulation model, VISION, to capture the relationships, timing and delays in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works and can transition as technologies are changed. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model and some examples of how to use VISION.

  9. VISION: Verifiable Fuel Cycle Simulation Model

    SciTech Connect

    Jacob Jacobson; A. M. Yacout; Gretchen Matthern; Steven Piet; David Shropshire; Tyler Schweitzer

    2010-11-01

    The nuclear fuel cycle consists of a set of complex components that work together in unison. In order to support the nuclear renaissance, it is necessary to understand the impacts of changes and timing of events in any part of the fuel cycle system. The Advanced Fuel Cycle Initiative’s systems analysis group is developing a dynamic simulation model, VISION, to capture the relationships, timing, and changes in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model components and some examples of how to use VISION.

  10. At the Biological Modeling and Simulation Frontier

    PubMed Central

    Ropella, Glen E. P.; Lam, Tai Ning; Tang, Jonathan; Kim, Sean H. J.; Engelberg, Jesse A.; Sheikh-Bahaei, Shahab

    2009-01-01

    We provide a rationale for and describe examples of synthetic modeling and simulation (M&S) of biological systems. We explain how synthetic methods are distinct from familiar inductive methods. Synthetic M&S is a means to better understand the mechanisms that generate normal and disease-related phenomena observed in research, and how compounds of interest interact with them to alter phenomena. An objective is to build better, working hypotheses of plausible mechanisms. A synthetic model is an extant hypothesis: execution produces an observable mechanism and phenomena. Mobile objects representing compounds carry information enabling components to distinguish between them and react accordingly when different compounds are studied simultaneously. We argue that the familiar inductive approaches contribute to the general inefficiencies being experienced by pharmaceutical R&D, and that use of synthetic approaches accelerates and improves R&D decision-making and thus the drug development process. A reason is that synthetic models encourage and facilitate abductive scientific reasoning, a primary means of knowledge creation and creative cognition. When synthetic models are executed, we observe different aspects of knowledge in action from different perspectives. These models can be tuned to reflect differences in experimental conditions and individuals, making translational research more concrete while moving us closer to personalized medicine. Electronic supplementary material The online version of this article (doi:10.1007/s11095-009-9958-3) contains supplementary material, which is available to authorized users. PMID:19756975

  11. Detailed simulation of morphodynamics: 1. Hydrodynamic model

    NASA Astrophysics Data System (ADS)

    Nabi, M.; de Vriend, H. J.; Mosselman, E.; Sloff, C. J.; Shimizu, Y.

    2012-12-01

    We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The grid can be locally refined and adapted to the bed geometry, managing the Cartesian grid cells and faces using a hierarchical tree data approach. A ghost-cell immersed-boundary technique is applied to cells intersecting the bed topography. The governing equations have been discretized using a finite-volume method on a staggered grid, conserving second-order accuracy in time and space. The solution advances in time using the fractional step approach. Large-eddy simulation is used as turbulence closure. We validate the model against several experiments and other results from literature. Model results for Stokes flow around a cylinder in the vicinity of a moving wall agree well with Wannier's analytical solution. At higher Reynolds numbers, computed trailing bubble length, separation angle, and drag coefficient compare favorably with experimental and previous computational results. Results for the flow over two- and three-dimensional dunes agree well with published data, including a fair reproduction of recirculation zones, horse-shoe structures, and boiling effects. This shows that the model is suitable for being used as a hydrodynamic submodel in the high-resolution modeling of sediment transport and formation and evolution of subaqueous ripples and dunes.

  12. Braiding DNA: experiments, simulations, and models.

    PubMed

    Charvin, G; Vologodskii, A; Bensimon, D; Croquette, V

    2005-06-01

    DNA encounters topological problems in vivo because of its extended double-helical structure. As a consequence, the semiconservative mechanism of DNA replication leads to the formation of DNA braids or catenanes, which have to be removed for the completion of cell division. To get a better understanding of these structures, we have studied the elastic behavior of two braided nicked DNA molecules using a magnetic trap apparatus. The experimental data let us identify and characterize three regimes of braiding: a slightly twisted regime before the formation of the first crossing, followed by genuine braids which, at large braiding number, buckle to form plectonemes. Two different approaches support and quantify this characterization of the data. First, Monte Carlo (MC) simulations of braided DNAs yield a full description of the molecules' behavior and their buckling transition. Second, modeling the braids as a twisted swing provides a good approximation of the elastic response of the molecules as they are intertwined. Comparisons of the experiments and the MC simulations with this analytical model allow for a measurement of the diameter of the braids and its dependence upon entropic and electrostatic repulsive interactions. The MC simulations allow for an estimate of the effective torsional constant of the braids (at a stretching force F = 2 pN): C(b) approximately 48 nm (as compared with C approximately 100 nm for a single unnicked DNA). Finally, at low salt concentrations and for sufficiently large number of braids, the diameter of the braided molecules is observed to collapse to that of double-stranded DNA. We suggest that this collapse is due to the partial melting and fraying of the two nicked molecules and the subsequent right- or left-handed intertwining of the stretched single strands.

  13. Dimensions of Credibility in Models and Simulations

    NASA Technical Reports Server (NTRS)

    Steele, Martin J.

    2008-01-01

    Based on the National Aeronautics and Space Administration's (NASA's) work in developing a standard for models and simulations (M&S), the subject of credibility in M&S became a distinct focus. This is an indirect result from the Space Shuttle Columbia Accident Investigation Board (CAIB), which eventually resulted in an action, among others, to improve the rigor in NASA's M&S practices. The focus of this action came to mean a standardized method for assessing and reporting results from any type of M&S. As is typical in the standards development process, this necessarily developed into defming a common terminology base, common documentation requirements (especially for M&S used in critical decision making), and a method for assessing the credibility of M&S results. What surfaced in the development of the NASA Standard was the various dimensions credibility to consider when accepting the results from any model or simulation analysis. The eight generally relevant factors of credibility chosen in the NASA Standard proved only one aspect in the dimensionality of M&S credibility. At the next level of detail, the full comprehension of some of the factors requires an understanding along a couple of dimensions as well. Included in this discussion are the prerequisites for the appropriate use of a given M&S, the choice of factors in credibility assessment with their inherent dimensionality, and minimum requirements for fully reporting M&S results.

  14. Modeling lift operations with SASmacr Simulation Studio

    NASA Astrophysics Data System (ADS)

    Kar, Leow Soo

    2016-10-01

    Lifts or elevators are an essential part of multistorey buildings which provide vertical transportation for its occupants. In large and high-rise apartment buildings, its occupants are permanent, while in buildings, like hospitals or office blocks, the occupants are temporary or users of the buildings. They come in to work or to visit, and thus, the population of such buildings are much higher than those in residential apartments. It is common these days that large office blocks or hospitals have at least 8 to 10 lifts serving its population. In order to optimize the level of service performance, different transportation schemes are devised to control the lift operations. For example, one lift may be assigned to solely service the even floors and another solely for the odd floors, etc. In this paper, a basic lift system is modelled using SAS Simulation Studio to study the effect of factors such as the number of floors, capacity of the lift car, arrival rate and exit rate of passengers at each floor, peak and off peak periods on the system performance. The simulation is applied to a real lift operation in Sunway College's North Building to validate the model.

  15. Simulation Modelling: Educational Development Roles for Learning Technologists.

    ERIC Educational Resources Information Center

    Riley, David

    2002-01-01

    Discusses computer assisted learning and simulation modeling from a United Kingdom perspective. Highlights include modeling with the DMS (Dynamic Modelling System); modeling with STELLA; learning and teaching simulation modeling; educational development roles for learning technologists; and a list of relevant Web sites. (Contains 52 references.)…

  16. Modeling and simulation of cascading contingencies

    NASA Astrophysics Data System (ADS)

    Zhang, Jianfeng

    This dissertation proposes a new approach to model and study cascading contingencies in large power systems. The most important contribution of the work involves the development and validation of a heuristic analytic model to assess the likelihood of cascading contingencies, and the development and validation of a uniform search strategy. We model the probability of cascading contingencies as a function of power flow and power flow changes. Utilizing logistic regression, the proposed model is calibrated using real industry data. This dissertation analyzes random search strategies for Monte Carlo simulations and proposes a new uniform search strategy based on the Metropolis-Hastings Algorithm. The proposed search strategy is capable of selecting the most significant cascading contingencies, and it is capable of constructing an unbiased estimator to provide a measure of system security. This dissertation makes it possible to reasonably quantify system security and justify security operations when economic concerns conflict with reliability concerns in the new competitive power market environment. It can also provide guidance to system operators about actions that may be taken to reduce the risk of major system blackouts. Various applications can be developed to take advantage of the quantitative security measures provided in this dissertation.

  17. Cognitive Modeling for Agent-Based Simulation of Child Maltreatment

    NASA Astrophysics Data System (ADS)

    Hu, Xiaolin; Puddy, Richard

    This paper extends previous work to develop cognitive modeling for agent-based simulation of child maltreatment (CM). The developed model is inspired from parental efficacy, parenting stress, and the theory of planned behavior. It provides an explanatory, process-oriented model of CM and incorporates causality relationship and feedback loops from different factors in the social ecology in order for simulating the dynamics of CM. We describe the model and present simulation results to demonstrate the features of this model.

  18. Modeling human response errors in synthetic flight simulator domain

    NASA Technical Reports Server (NTRS)

    Ntuen, Celestine A.

    1992-01-01

    This paper presents a control theoretic approach to modeling human response errors (HRE) in the flight simulation domain. The human pilot is modeled as a supervisor of a highly automated system. The synthesis uses the theory of optimal control pilot modeling for integrating the pilot's observation error and the error due to the simulation model (experimental error). Methods for solving the HRE problem are suggested. Experimental verification of the models will be tested in a flight quality handling simulation.

  19. Modeling, Simulation and Visualization of Aerocapture

    NASA Astrophysics Data System (ADS)

    leszcynski, Zigmond V.

    1998-12-01

    A vehicle travelling from Earth to another planet on a ballistic trajectory approaches that planet at hyperbolic velocity. Upon arrival, the vehicle must significantly reduce its speed for orbit insertion. Traditionally, this deceleration has been achieved by propulsive capture, which consumes a large amount of propellant. Aerocapture offers a more fuel-efficient alternative by exploiting vehicular drag in the planet's atmosphere. However, this technique generates extreme heat, necessitating a special thermal protection shield (TPS). Performing a trade study between the propellant mass required for propulsive capture and the TPS mass required for aerocapture can help determine which method is more desirable for a particular mission. The research objective of this thesis was to analyze aerocapture dynamics for the advancement of this trade study process. The result was an aerocapture simulation tool (ACAPS) developed in MATLAB with SIMULINK, emphasizing code validation, upgradeability, user-friendliness and trajectory visualization. The current version, ACAPS 1.1, is a three- degrees-of-freedom point mass simulation model that incorporates a look-up table for the Mars atmosphere. ACAPS is expected to supplement the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) Project Design Center (PDC) toolkit as preliminary design software for the Mars 2005 Sample Return (MSR) Mission, Mars 2007 Mission, Mars Micromissions, Neptune/Triton Mission, and Human Mars Mission.

  20. LADEE Satellite Modeling and Simulation Development

    NASA Technical Reports Server (NTRS)

    Adams, Michael; Cannon, Howard; Frost, Chad

    2011-01-01

    As human activity on and around the Moon increases, so does the likelihood that our actions will have an impact on its atmosphere. The Lunar Atmosphere and Dust Environment Explorer (LADEE), a NASA satellite scheduled to launch in 2013, will orbit the Moon collecting composition, density, and time variability data to characterize the current state of the lunar atmosphere. LADEE will also test the concept of the "Modular Common Bus" spacecraft architecture, an effort to reduce both development time and cost by designing reusable, modular components for use in multiple missions with similar requirements. An important aspect of this design strategy is to both simulate the spacecraft and develop the flight code in Simulink, a block diagram-style programming language that allows easy algorithm visualization and performance testing. Before flight code can be tested, however, a realistic simulation of the satellite and its dynamics must be generated and validated. This includes all of the satellite control system components such as actuators used for force and torque generation and sensors used for inertial orientation reference. My primary responsibilities have included designing, integrating, and testing models for the LADEE thrusters, reaction wheels, star trackers, and rate gyroscopes.

  1. Modeling and simulation of a biofilter

    SciTech Connect

    Amanullah, M.; Farooq, S.; Viswanathan, S.

    1999-07-01

    Treatment of air streams contaminated with volatile organic compounds in a biofilter under transient and steady-state conditions of operation is described with a mathematical model. The model incorporates convection and dispersion in the gas phase, partial coverage of the solid support, interphase mass transfer between the gas and the aqueous biofilm with an equilibrium partition at the interface followed by diffusion, direct adsorption to the exposed uncovered solid adsorbent media, transfer between the biofilm and the solid support, and biological reactions in both the biofilm and the adsorbent. The model equations were solved numerically by the method of orthogonal collocation using a MATLAB computer code. The effects of pollutant dispersion in the gas phase, specific surface area available for mass transfer, thickness of the biofilm, and adsorptive capacity of the solid support on the biofilter performance were investigated in detail. The steady-state removal efficiency appears to be nearly independent of gas-phase dispersion of the pollutant in the normal industrial range of operations. Results also indicate that the biofilter performance is a strong function of specific surface area for mass transfer and biofilm thickness. Simulation results further suggest that higher adsorptive support media are capable of handling load fluctuations irrespective of the rate of reaction in the adsorbed phase.

  2. Large-eddy simulations with wall models

    NASA Technical Reports Server (NTRS)

    Cabot, W.

    1995-01-01

    The near-wall viscous and buffer regions of wall-bounded flows generally require a large expenditure of computational resources to be resolved adequately, even in large-eddy simulation (LES). Often as much as 50% of the grid points in a computational domain are devoted to these regions. The dense grids that this implies also generally require small time steps for numerical stability and/or accuracy. It is commonly assumed that the inner wall layers are near equilibrium, so that the standard logarithmic law can be applied as the boundary condition for the wall stress well away from the wall, for example, in the logarithmic region, obviating the need to expend large amounts of grid points and computational time in this region. This approach is commonly employed in LES of planetary boundary layers, and it has also been used for some simple engineering flows. In order to calculate accurately a wall-bounded flow with coarse wall resolution, one requires the wall stress as a boundary condition. The goal of this work is to determine the extent to which equilibrium and boundary layer assumptions are valid in the near-wall regions, to develop models for the inner layer based on such assumptions, and to test these modeling ideas in some relatively simple flows with different pressure gradients, such as channel flow and flow over a backward-facing step. Ultimately, models that perform adequately in these situations will be applied to more complex flow configurations, such as an airfoil.

  3. Modelling and Simulation of Search Engine

    NASA Astrophysics Data System (ADS)

    Nasution, Mahyuddin K. M.

    2017-01-01

    The best tool currently used to access information is a search engine. Meanwhile, the information space has its own behaviour. Systematically, an information space needs to be familiarized with mathematics so easily we identify the characteristics associated with it. This paper reveal some characteristics of search engine based on a model of document collection, which are then estimated the impact on the feasibility of information. We reveal some of characteristics of search engine on the lemma and theorem about singleton and doubleton, then computes statistically characteristic as simulating the possibility of using search engine. In this case, Google and Yahoo. There are differences in the behaviour of both search engines, although in theory based on the concept of documents collection.

  4. Biodiversity on island chains: Neutral model simulations

    NASA Astrophysics Data System (ADS)

    Warren, Patrick B.

    2010-11-01

    A neutral ecology model is simulated on an island chain, in which neighboring islands can exchange individuals but only the first island is able to receive immigrants from a metacommunity. It is found by several measures that α -diversity decreases along the chain. Subtle changes in taxon abundance distributions can be detected when islands in the chain are compared to diversity-matched single islands. The island chain is found to have unexpectedly rich dynamics. Significant β -diversity correlations are found between islands in the chain, which are absent between diversity-matched single islands. The results potentially apply to human microbial biodiversity and biogeography and suggest that measurements of interindividual and intraindividual β -diversity may give insights into microbial community assembly mechanisms.

  5. Model Simulations of Waves in Hurricane Juan

    NASA Astrophysics Data System (ADS)

    Perrie, W.; Toulany, B.; Padilla-Hernandez, R.; Hu, Y.; Smith, P.; Zhang, W.; Zou, Q.; Ren, X.

    2004-05-01

    Hurricane Juan made landfall at 0300 UTC near Halifax Nova Scotia. This was a category 2 hurricane with winds of 44 m/s, the largest storm to pass over these coastal areas in several decades. Associated high ocean waves were experienced in coastal waters, from Peggy's Cove to Sheet Harbour, growing to epic proportions on the Scotian Shelf, and exceeding the 100-year return wave based on the present climatology. As part of the GoMOOS program (Gulf of Maine Ocean Observing System, www.gomoos.org), winds from the USA Navy COAMPS (Coupled Ocean Atmosphere Model Prediction System) were used to evaluate and compare three widely-used third generation numerical wave models, SWAN, WAM and WaveWatch-III (hereafter WW3) for accuracy, with in situ measurements. Model comparisons consist of a set of composite model systems, respectively nesting WAM, WW3 and SWAN in WAM and WW3. We report results from the intermediate-resolution grid for Hurricane Juan. Wave measurements were made using four operational deep-water buoys (C44258, C44142, C44137, 44005), by a conventional directional wave rider (DWR) moored offshore from Lunenburg Bay, and also by two acoustic Doppler current profiler (ADCP) located (1) near an oil rig on Sable Island Bank, in relatively shallow water, and (2) near the outer boundary of Lunenburg Bay. We discuss the reliability of DWR wave data compared to ADCP wave data. We show that all models provide reliable hindcasts for significant wave height (Hs) and for peak period (Tp) for Juan, although a clear under-estimation of Hs at the peak of the storm is evident, compared to observations. A feature in the COAMPS storm simulation is that the storm track appears to be slightly to the east of that of Quikscat scatterometer data. Comparisons between models and 2-dimensional wave spectra are presented. Preliminary results suggest that the recently released upgrade to the WW3 model shows slightly enhanced skill compared to the other models.

  6. Modeling active memory: Experiment, theory and simulation

    NASA Astrophysics Data System (ADS)

    Amit, Daniel J.

    2001-06-01

    Neuro-physiological experiments on cognitively performing primates are described to argue that strong evidence exists for localized, non-ergodic (stimulus specific) attractor dynamics in the cortex. The specific phenomena are delay activity distributions-enhanced spike-rate distributions resulting from training, which we associate with working memory. The anatomy of the relevant cortex region and the physiological characteristics of the participating elements (neural cells) are reviewed to provide a substrate for modeling the observed phenomena. Modeling is based on the properties of the integrate-and-fire neural element in presence of an input current of Gaussian distribution. Theory of stochastic processes provides an expression for the spike emission rate as a function of the mean and the variance of the current distribution. Mean-field theory is then based on the assumption that spike emission processes in different neurons in the network are independent, and hence the input current to a neuron is Gaussian. Consequently, the dynamics of the interacting network is reduced to the computation of the mean and the variance of the current received by a cell of a given population in terms of the constitutive parameters of the network and the emission rates of the neurons in the different populations. Within this logic we analyze the stationary states of an unstructured network, corresponding to spontaneous activity, and show that it can be stable only if locally the net input current of a neuron is inhibitory. This is then tested against simulations and it is found that agreement is excellent down to great detail. A confirmation of the independence hypothesis. On top of stable spontaneous activity, keeping all parameters fixed, training is described by (Hebbian) modification of synapses between neurons responsive to a stimulus and other neurons in the module-synapses are potentiated between two excited neurons and depressed between an excited and a quiescent neuron

  7. Model-free simulations of turbulent reactive flows

    NASA Technical Reports Server (NTRS)

    Givi, Peyman

    1989-01-01

    The current computational methods for solving transport equations of turbulent reacting single-phase flows are critically reviewed, with primary attention given to those methods that lead to model-free simulations. In particular, consideration is given to direct numerical simulations using spectral (Galerkin) and pseudospectral (collocation) methods, spectral element methods, and Lagrangian methods. The discussion also covers large eddy simulations and turbulence modeling.

  8. Using Computational Simulations to Confront Students' Mental Models

    ERIC Educational Resources Information Center

    Rodrigues, R.; Carvalho, P. Simeão

    2014-01-01

    In this paper we show an example of how to use a computational simulation to obtain visual feedback for students' mental models, and compare their predictions with the simulated system's behaviour. Additionally, we use the computational simulation to incrementally modify the students' mental models in order to accommodate new data,…

  9. A Geostationary Earth Orbit Satellite Model Using Easy Java Simulation

    ERIC Educational Resources Information Center

    Wee, Loo Kang; Goh, Giam Hwee

    2013-01-01

    We develop an Easy Java Simulation (EJS) model for students to visualize geostationary orbits near Earth, modelled using a Java 3D implementation of the EJS 3D library. The simplified physics model is described and simulated using a simple constant angular velocity equation. We discuss four computer model design ideas: (1) a simple and realistic…

  10. The modeling of miniature UAV flight visualization simulation platform

    NASA Astrophysics Data System (ADS)

    Li, Dong-hui; Li, Xin; Yang, Le-le; Li, Xiong

    2015-12-01

    This paper combines virtual technology with visualization visual simulation theory, construct the framework of visual simulation platform, apply open source software FlightGear simulator combined with GoogleEarth design a small UAV flight visual simulation platform. Using software AC3D to build 3D models of aircraft and complete the model loading based on XML configuration, the design and simulation of visualization modeling visual platform is presented. By using model-driven and data transforming in FlightGear , the design of data transmission module is realized based on Visual Studio 2010 development platform. Finally combined with GoogleEarth it can achieve the tracking and display.

  11. Modeling and Simulation at Tidewater Community College

    NASA Technical Reports Server (NTRS)

    Summers, Michael

    2008-01-01

    Investment of $1.5 million in medical simulation technology. Integration of medical simulation activities into the curriculum. Support from TCC leadership. Individual and team activities. Skill development and critical thinking/problem solving skills.

  12. Modelling toolkit for simulation of maglev devices

    NASA Astrophysics Data System (ADS)

    Peña-Roche, J.; Badía-Majós, A.

    2017-01-01

    A stand-alone App1 has been developed, focused on obtaining information about relevant engineering properties of magnetic levitation systems. Our modelling toolkit provides real time simulations of 2D magneto-mechanical quantities for superconductor (SC)/permanent magnet structures. The source code is open and may be customised for a variety of configurations. Ultimately, it relies on the variational statement of the critical state model for the superconducting component and has been verified against experimental data for YBaCuO/NdFeB assemblies. On a quantitative basis, the values of the arising forces, induced superconducting currents, as well as a plot of the magnetic field lines are displayed upon selection of an arbitrary trajectory of the magnet in the vicinity of the SC. The stability issues related to the cooling process, as well as the maximum attainable forces for a given material and geometry are immediately observed. Due to the complexity of the problem, a strategy based on cluster computing, database compression, and real-time post-processing on the device has been implemented.

  13. Stratospheric Temperature Changes: Observations and Model Simulations

    NASA Technical Reports Server (NTRS)

    Ramaswamy, V.; Chanin, M.-L.; Angell, J.; Barnett, J.; Gaffen, D.; Gelman, M.; Keckhut, P.; Koshelkov, Y.; Labitzke, K.; Lin, J.-J. R.

    1999-01-01

    This paper reviews observations of stratospheric temperatures that have been made over a period of several decades. Those observed temperatures have been used to assess variations and trends in stratospheric temperatures. A wide range of observation datasets have been used, comprising measurements by radiosonde (1940s to the present), satellite (1979 - present), lidar (1979 - present) and rocketsonde (periods varying with location, but most terminating by about the mid-1990s). In addition, trends have also been assessed from meteorological analyses, based on radiosonde and/or satellite data, and products based on assimilating observations into a general circulation model. Radiosonde and satellite data indicate a cooling trend of the annual-mean lower stratosphere since about 1980. Over the period 1979-1994, the trend is 0.6K/decade. For the period prior to 1980, the radiosonde data exhibit a substantially weaker long-term cooling trend. In the northern hemisphere, the cooling trend is about 0.75K/decade in the lower stratosphere, with a reduction in the cooling in mid-stratosphere (near 35 km), and increased cooling in the upper stratosphere (approximately 2 K per decade at 50 km). Model simulations indicate that the depletion of lower stratospheric ozone is the dominant factor in the observed lower stratospheric cooling. In the middle and upper stratosphere both the well-mixed greenhouse gases (such as CO) and ozone changes contribute in an important manner to the cooling.

  14. Reusable Component Model Development Approach for Parallel and Distributed Simulation

    PubMed Central

    Zhu, Feng; Yao, Yiping; Chen, Huilong; Yao, Feng

    2014-01-01

    Model reuse is a key issue to be resolved in parallel and distributed simulation at present. However, component models built by different domain experts usually have diversiform interfaces, couple tightly, and bind with simulation platforms closely. As a result, they are difficult to be reused across different simulation platforms and applications. To address the problem, this paper first proposed a reusable component model framework. Based on this framework, then our reusable model development approach is elaborated, which contains two phases: (1) domain experts create simulation computational modules observing three principles to achieve their independence; (2) model developer encapsulates these simulation computational modules with six standard service interfaces to improve their reusability. The case study of a radar model indicates that the model developed using our approach has good reusability and it is easy to be used in different simulation platforms and applications. PMID:24729751

  15. Mathematical Modeling and Simulation of Seated Stability

    PubMed Central

    Tanaka, Martin L.; Ross, Shane D.; Nussbaum, Maury A.

    2009-01-01

    Various methods have been used to quantify the kinematic variability or stability of the human spine. However, each of these methods evaluates dynamic behavior within the stable region of state space. In contrast, our goal was to determine the extent of the stable region. A 2D mathematical model was developed for a human sitting on an unstable seat apparatus (i.e., the “wobble chair”). Forward dynamic simulations were used to compute trajectories based on the initial state. From these trajectories, a scalar field of trajectory divergence was calculated, specifically a finite time Lyapunov exponent (FTLE) field. Theoretically, ridges of local maxima within this field are expected to partition the state space into regions of qualitatively different behavior. We found that ridges formed at the boundary between regions of stability and failure (i.e., falling). The location of the basin of stability found using the FTLE field matched well with the basin of stability determined by an alternative method. In addition, an equilibrium manifold was found, which describes a set of equilibrium configurations that act as a low dimensional attractor in the controlled system. These simulations are a first step in developing a method to locate state space boundaries for torso stability. Identifying these boundaries may provide a framework for assessing factors that contribute to health risks associated with spinal injury and poor balance recovery (e.g., age, fatigue, load/weight and distribution). Furthermore, an approach is presented that can be adapted to find state space boundaries in other biomechanical applications. PMID:20018288

  16. Developments in Atmosphere Revitalization Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Kittredge, Kenneth; Xoker, Robert F.; Cummings, Ramona; Gomez, Carlos F.

    2012-01-01

    "NASA's Advanced Exploration Systems (AES) program is pioneering new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit" (NASA 2012). These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must not only blast out of earth's gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by evaluating structured sorbents, seeking more robust pelletized sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach, which is then implemented in a full-scale integrated atmosphere revitalization test. This paper describes the development of atmosphere revitalization models and simulations. A companion paper discusses the hardware design and sorbent screening and characterization effort in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project within the AES program.

  17. Predictive Capability Maturity Model for computational modeling and simulation.

    SciTech Connect

    Oberkampf, William Louis; Trucano, Timothy Guy; Pilch, Martin M.

    2007-10-01

    The Predictive Capability Maturity Model (PCMM) is a new model that can be used to assess the level of maturity of computational modeling and simulation (M&S) efforts. The development of the model is based on both the authors experience and their analysis of similar investigations in the past. The perspective taken in this report is one of judging the usefulness of a predictive capability that relies on the numerical solution to partial differential equations to better inform and improve decision making. The review of past investigations, such as the Software Engineering Institute's Capability Maturity Model Integration and the National Aeronautics and Space Administration and Department of Defense Technology Readiness Levels, indicates that a more restricted, more interpretable method is needed to assess the maturity of an M&S effort. The PCMM addresses six contributing elements to M&S: (1) representation and geometric fidelity, (2) physics and material model fidelity, (3) code verification, (4) solution verification, (5) model validation, and (6) uncertainty quantification and sensitivity analysis. For each of these elements, attributes are identified that characterize four increasing levels of maturity. Importantly, the PCMM is a structured method for assessing the maturity of an M&S effort that is directed toward an engineering application of interest. The PCMM does not assess whether the M&S effort, the accuracy of the predictions, or the performance of the engineering system satisfies or does not satisfy specified application requirements.

  18. Aircraft vulnerability analysis by modeling and simulation

    NASA Astrophysics Data System (ADS)

    Willers, Cornelius J.; Willers, Maria S.; de Waal, Alta

    2014-10-01

    guidance acceleration and seeker sensitivity. For the purpose of this investigation the aircraft is equipped with conventional pyrotechnic decoy flares and the missile has no counter-countermeasure means (security restrictions on open publication). This complete simulation is used to calculate the missile miss distance, when the missile is launched from different locations around the aircraft. The miss distance data is then graphically presented showing miss distance (aircraft vulnerability) as a function of launch direction and range. The aircraft vulnerability graph accounts for aircraft and missile characteristics, but does not account for missile deployment doctrine. A Bayesian network is constructed to fuse the doctrinal rules with the aircraft vulnerability data. The Bayesian network now provides the capability to evaluate the combined risk of missile launch and aircraft vulnerability. It is shown in this paper that it is indeed possible to predict the aircraft vulnerability to missile attack in a comprehensive modelling and a holistic process. By using the appropriate real-world models, this approach is used to evaluate the effectiveness of specific countermeasure techniques against specific missile threats. The use of a Bayesian network provides the means to fuse simulated performance data with more abstract doctrinal rules to provide a realistic assessment of the aircraft vulnerability.

  19. An electrical circuit model for simulation of indoor radon concentration.

    PubMed

    Musavi Nasab, S M; Negarestani, A

    2013-01-01

    In this study, a new model based on electric circuit theory was introduced to simulate the behaviour of indoor radon concentration. In this model, a voltage source simulates radon generation in walls, conductivity simulates migration through walls and voltage across a capacitor simulates radon concentration in a room. This simulation considers migration of radon through walls by diffusion mechanism in one-dimensional geometry. Data reported in a typical Greek house were employed to examine the application of this technique of simulation to the behaviour of radon.

  20. Georeferenced model simulations efficiently support targeted monitoring

    NASA Astrophysics Data System (ADS)

    Berlekamp, Jürgen; Klasmeier, Jörg

    2010-05-01

    The European Water Framework Directive (WFD) demands the good ecological and chemical status of surface waters. To meet the definition of good chemical status of the WFD surface water concentrations of priority pollutants must not exceed established environmental quality standards (EQS). Surveillance of the concentrations of numerous chemical pollutants in whole river basins by monitoring is laborious and time-consuming. Moreover, measured data do often not allow for immediate source apportionment which is a prerequisite for defining promising reduction strategies to be implemented within the programme of measures. In this context, spatially explicit model approaches are highly advantageous because they provide a direct link between local point emissions (e.g. treated wastewater) or diffuse non-point emissions (e.g. agricultural runoff) and resulting surface water concentrations. Scenario analyses with such models allow for a priori investigation of potential positive effects of reduction measures such as optimization of wastewater treatment. The geo-referenced model GREAT-ER (Geography-referenced Regional Exposure Assessment Tool for European Rivers) has been designed to calculate spatially resolved averaged concentrations for different flow conditions (e.g. mean or low flow) based on emission estimations for local point source emissions such as treated effluents from wastewater treatment plants. The methodology was applied to selected pharmaceuticals (diclofenac, sotalol, metoprolol, carbamazepin) in the Main river basin in Germany (approx. 27,290 km²). Average concentrations of the compounds were calculated for each river reach in the whole catchment. Simulation results were evaluated by comparison with available data from orienting monitoring and used to develop an optimal monitoring strategy for the assessment of water quality regarding micropollutants at the catchment scale.

  1. Beyond Modeling: All-Atom Olfactory Receptor Model Simulations

    PubMed Central

    Lai, Peter C.; Crasto, Chiquito J.

    2012-01-01

    Olfactory receptors (ORs) are a type of GTP-binding protein-coupled receptor (GPCR). These receptors are responsible for mediating the sense of smell through their interaction with odor ligands. OR-odorant interactions marks the first step in the process that leads to olfaction. Computational studies on model OR structures can generate focused and novel hypotheses for further bench investigation by providing a view of these interactions at the molecular level beyond inferences that are drawn merely from static docking. Here we have shown the specific advantages of simulating the dynamic environment associated with OR-odorant interactions. We present a rigorous protocol which ranges from the creation of a computationally derived model of an olfactory receptor to simulating the interactions between an OR and an odorant molecule. Given the ubiquitous occurrence of GPCRs in the membranes of cells, we anticipate that our OR-developed methodology will serve as a model for the computational structural biology of all GPCRs. PMID:22563330

  2. Simulation modeling for long duration spacecraft control systems

    NASA Astrophysics Data System (ADS)

    Boyd, Mark A.; Bavuso, Salvatore J.

    1993-12-01

    The use of simulation is described and it is contrasted to analytical solution techniques for evaluation of analytical reliability models. The role importance sampling plays in simulation of models of this type was also discussed. The simulator tool used for our analysis is described. Finally, the use of the simulator tool was demonstrated by applying it to evaluate the reliability of a fault tolerant hypercube multiprocessor intended for spacecraft designed for long duration missions. The reliability analysis was used to highlight the advantages and disadvantages offered by simulation over analytical solution of Markovian and non-Markovian reliability models.

  3. Simulation modeling for long duration spacecraft control systems

    NASA Technical Reports Server (NTRS)

    Boyd, Mark A.; Bavuso, Salvatore J.

    1993-01-01

    The use of simulation is described and it is contrasted to analytical solution techniques for evaluation of analytical reliability models. The role importance sampling plays in simulation of models of this type was also discussed. The simulator tool used for our analysis is described. Finally, the use of the simulator tool was demonstrated by applying it to evaluate the reliability of a fault tolerant hypercube multiprocessor intended for spacecraft designed for long duration missions. The reliability analysis was used to highlight the advantages and disadvantages offered by simulation over analytical solution of Markovian and non-Markovian reliability models.

  4. KU-Band rendezvous radar performance computer simulation model

    NASA Technical Reports Server (NTRS)

    Griffin, J. W.

    1980-01-01

    The preparation of a real time computer simulation model of the KU band rendezvous radar to be integrated into the shuttle mission simulator (SMS), the shuttle engineering simulator (SES), and the shuttle avionics integration laboratory (SAIL) simulator is described. To meet crew training requirements a radar tracking performance model, and a target modeling method were developed. The parent simulation/radar simulation interface requirements, and the method selected to model target scattering properties, including an application of this method to the SPAS spacecraft are described. The radar search and acquisition mode performance model and the radar track mode signal processor model are examined and analyzed. The angle, angle rate, range, and range rate tracking loops are also discussed.

  5. Kinetic plasma modeling with quiet Monte Carlo direct simulation.

    SciTech Connect

    Albright, B. J.; Jones, M. E.; Lemons, D. S.; Winske, D.

    2001-01-01

    The modeling of collisions among particles in space plasma media poses a challenge for computer simulation. Traditional plasma methods are able to model well the extremes of highly collisional plasmas (MHD and Hall-MHD simulations) and collisionless plasmas (particle-in-cell simulations). However, neither is capable of trealing the intermediate, semi-collisional regime. The authors have invented a new approach to particle simulation called Quiet Monte Carlo Direct Simulation (QMCDS) that can, in principle, treat plasmas with arbitrary and arbitrarily varying collisionality. The QMCDS method will be described, and applications of the QMCDS method as 'proof of principle' to diffusion, hydrodynamics, and radiation transport will be presented. Of particular interest to the space plasma simulation community is the application of QMCDS to kinetic plasma modeling. A method for QMCDS simulation of kinetic plasmas will be outlined, and preliminary results of simulations in the limit of weak pitch-angle scattering will be presented.

  6. Simulation Modeling of a Facility Layout in Operations Management Classes

    ERIC Educational Resources Information Center

    Yazici, Hulya Julie

    2006-01-01

    Teaching quantitative courses can be challenging. Similarly, layout modeling and lean production concepts can be difficult to grasp in an introductory OM (operations management) class. This article describes a simulation model developed in PROMODEL to facilitate the learning of layout modeling and lean manufacturing. Simulation allows for the…

  7. Project Shuttle simulation math model coordination catalog, revision 1

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A catalog is presented of subsystem and environment math models used or planned for space shuttle simulations. The purpose is to facilitate sharing of similar math models between shuttle simulations. It provides information on mach model requirements, formulations, schedules, and contact persons for further information.

  8. Maneuver simulation model of an experimental hovercraft for the Antarctic

    NASA Astrophysics Data System (ADS)

    Murao, Rinichi

    Results of an investigation of a hovercraft model designed for Antarctic conditions are presented. The buoyancy characteristics, the propellant control system, and simulation model control are examined. An ACV (air cushion vehicle) model of the hovercraft is used to examine the flexibility and friction of the skirt. Simulation results are presented which show the performance of the hovercraft.

  9. Optical Imaging and Radiometric Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Ha, Kong Q.; Fitzmaurice, Michael W.; Moiser, Gary E.; Howard, Joseph M.; Le, Chi M.

    2010-01-01

    OPTOOL software is a general-purpose optical systems analysis tool that was developed to offer a solution to problems associated with computational programs written for the James Webb Space Telescope optical system. It integrates existing routines into coherent processes, and provides a structure with reusable capabilities that allow additional processes to be quickly developed and integrated. It has an extensive graphical user interface, which makes the tool more intuitive and friendly. OPTOOL is implemented using MATLAB with a Fourier optics-based approach for point spread function (PSF) calculations. It features parametric and Monte Carlo simulation capabilities, and uses a direct integration calculation to permit high spatial sampling of the PSF. Exit pupil optical path difference (OPD) maps can be generated using combinations of Zernike polynomials or shaped power spectral densities. The graphical user interface allows rapid creation of arbitrary pupil geometries, and entry of all other modeling parameters to support basic imaging and radiometric analyses. OPTOOL provides the capability to generate wavefront-error (WFE) maps for arbitrary grid sizes. These maps are 2D arrays containing digital sampled versions of functions ranging from Zernike polynomials to combination of sinusoidal wave functions in 2D, to functions generated from a spatial frequency power spectral distribution (PSD). It also can generate optical transfer functions (OTFs), which are incorporated into the PSF calculation. The user can specify radiometrics for the target and sky background, and key performance parameters for the instrument s focal plane array (FPA). This radiometric and detector model setup is fairly extensive, and includes parameters such as zodiacal background, thermal emission noise, read noise, and dark current. The setup also includes target spectral energy distribution as a function of wavelength for polychromatic sources, detector pixel size, and the FPA s charge

  10. Modeling and Performance Simulation of the Mass Storage Network Environment

    NASA Technical Reports Server (NTRS)

    Kim, Chan M.; Sang, Janche

    2000-01-01

    This paper describes the application of modeling and simulation in evaluating and predicting the performance of the mass storage network environment. Network traffic is generated to mimic the realistic pattern of file transfer, electronic mail, and web browsing. The behavior and performance of the mass storage network and a typical client-server Local Area Network (LAN) are investigated by modeling and simulation. Performance characteristics in throughput and delay demonstrate the important role of modeling and simulation in network engineering and capacity planning.

  11. Hybrid Concurrent Constraint Simulation Models of Several Systems

    NASA Technical Reports Server (NTRS)

    Sweet, Adam

    2003-01-01

    This distribution contains several simulation models created for the hybrid simulation language, Hybrid Concurrent Constraint (HCC). An HCC model contains the information specified in the widely-accepted academic definition of a hybrid system: this includes expressions for the modes of the systems to be simulated and the differential equations that apply in each mode. These expressions are written in the HCC syntax. The models included here were created by either applying basic physical laws or implementing equations listed in previously published papers.

  12. The COD Model: Simulating Workgroup Performance

    NASA Astrophysics Data System (ADS)

    Biggiero, Lucio; Sevi, Enrico

    Though the question of the determinants of workgroup performance is one of the most central in organization science, precise theoretical frameworks and formal demonstrations are still missing. In order to fill in this gap the COD agent-based simulation model is here presented and used to study the effects of task interdependence and bounded rationality on workgroup performance. The first relevant finding is an algorithmic demonstration of the ordering of interdependencies in terms of complexity, showing that the parallel mode is the most simplex, followed by the sequential and then by the reciprocal. This result is far from being new in organization science, but what is remarkable is that now it has the strength of an algorithmic demonstration instead of being based on the authoritativeness of some scholar or on some episodic empirical finding. The second important result is that the progressive introduction of realistic limits to agents' rationality dramatically reduces workgroup performance and addresses to a rather interesting result: when agents' rationality is severely bounded simple norms work better than complex norms. The third main finding is that when the complexity of interdependence is high, then the appropriate coordination mechanism is agents' direct and active collaboration, which means teamwork.

  13. Diversity modelling for electrical power system simulation

    NASA Astrophysics Data System (ADS)

    Sharip, R. M.; Abu Zarim, M. A. U. A.

    2013-12-01

    This paper considers diversity of generation and demand profiles against the different future energy scenarios and evaluates these on a technical basis. Compared to previous studies, this research applied a forecasting concept based on possible growth rates from publically electrical distribution scenarios concerning the UK. These scenarios were created by different bodies considering aspects such as environment, policy, regulation, economic and technical. In line with these scenarios, forecasting is on a long term timescale (up to every ten years from 2020 until 2050) in order to create a possible output of generation mix and demand profiles to be used as an appropriate boundary condition for the network simulation. The network considered is a segment of rural LV populated with a mixture of different housing types. The profiles for the 'future' energy and demand have been successfully modelled by applying a forecasting method. The network results under these profiles shows for the cases studied that even though the value of the power produced from each Micro-generation is often in line with the demand requirements of an individual dwelling there will be no problems arising from high penetration of Micro-generation and demand side management for each dwellings considered. The results obtained highlight the technical issues/changes for energy delivery and management to rural customers under the future energy scenarios.

  14. Behavioral model simulation studies of an image compressor. Thesis

    NASA Technical Reports Server (NTRS)

    Madani, Navid; Whitaker, Sterling

    1993-01-01

    The high initial cost of prototype Very Large Scaled Integrated (VLSI) parts requires that sufficient verifications be made to eliminate design errors before actually producing the prototypes. Logic simulation is the means by which the VLSI engineer can ensure that the design will function properly. The computer time required for logic simulation can be reduced through the use of behavioral models. Behavioral models, however, require time to write and verify and they do not always produce a dramatic speed up in logic simulation time. This paper presents a study of behavioral modeling aimed at discovering which circuit types benefit most from the use of behavioral models for logic simulation.

  15. Simulating wheat crop residue reflectance with the SAIL model.

    SciTech Connect

    Su, H.; Ransom, M. D.; Kanemasu, E. T.; Environmental Assessment; Kansas State Univ.; Univ. of Georgia

    1997-01-01

    Estimating crop residue is important for soil conservation and tillage management. Remote sensing could provide the potential of estimating amount of crop residue using reflectance measurement and model simulation procedures. The purpose of this study was (1) to use the SAIL (Scattering by Arbitrarily Inclined Leaves) model to simulate crop residue reflectance from wheat, Triticum aestivum (L.), at visible and near-infrared wavelengths; and (2) to compare the simulated reflectance with field-measured reflectance for evaluating the simulation model. Simulated reflectance in visible and near-infrared wavebands was overestimated about 1 to 5 per cent, compared with measured reflectance in the field. However, overestimation was within the experimental errors. Results suggest that the SAIL model can be used to simulate crop residue reflectance in different wheat crop residue covers and that wheat crop residue cover could be estimated by inverting the model.

  16. Model-Building Tools for Simulation-Based Training.

    ERIC Educational Resources Information Center

    Towne, Douglas M.; And Others

    1990-01-01

    Explains the Intelligent Maintenance Training System that allows a nonprogramming subject matter expert to produce an interactive graphical model of a complex device for computer simulation. Previous simulation-based training systems are reviewed; simulation algorithms are described; and the student interface is discussed. (Contains 24…

  17. Modeling Nanocomposites for Molecular Dynamics (MD) Simulations

    DTIC Science & Technology

    2015-01-01

    Maximum 200 Words) The minimum energy configuration for Molecular Dynamics (MD) simulations is found for a carbon nanotube (CNT)/polymer...Carbon Nanotubes (CNTs), Molecular Dynamics Simulations 15. NUMBER OF PAGES 18 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT...fiber composites have shown success in improving mechanical properties. Carbon nanotube (CNT)-based nanocomposites have been studied for

  18. Simulation Tools Model Icing for Aircraft Design

    NASA Technical Reports Server (NTRS)

    2012-01-01

    the years from strictly a research tool to one used routinely by industry and other government agencies. Glenn contractor William Wright has been the architect of this development, supported by a team of researchers investigating icing physics, creating validation data, and ensuring development according to standard software engineering practices. The program provides a virtual simulation environment for determining where water droplets strike an airfoil in flight, what kind of ice would result, and what shape that ice would take. Users can enter geometries for specific, two-dimensional cross sections of an airfoil or other airframe surface and then apply a range of inputs - different droplet sizes, temperatures, airspeeds, and more - to model how ice would build up on the surface in various conditions. The program s versatility, ease of use, and speed - LEWICE can run through complex icing simulations in only a few minutes - have contributed to it becoming a popular resource in the aviation industry.

  19. Theory, modeling and simulation of superconducting qubits

    SciTech Connect

    Berman, Gennady P; Kamenev, Dmitry I; Chumak, Alexander; Kinion, Carin; Tsifrinovich, Vladimir

    2011-01-13

    We analyze the dynamics of a qubit-resonator system coupled with a thermal bath and external electromagnetic fields. Using the evolution equations for the set of Heisenberg operators that describe the whole system, we derive an expression for the resonator field, that includes the resonator-drive, the resonator-bath, and resonator-qubit interactions. The renormalization of the resonator frequency, caused by the qubit-resonator interaction, is accounted for. Using the solutions for the resonator field, we derive the equation that describes the qubit dynamics. The dependence of the qubit evolution during the measurement time on the fidelity of a single-shot measurement is studied. The relation between the fidelity and measurement time is shown explicitly. We proposed a novel adiabatic method for the phase qubit measurement. The method utilizes a low-frequency, quasi-classical resonator inductively coupled to the qubit. The resonator modulates the qubit energy, and the back reaction of the qubit causes a shift in the phase of the resonator. The resonator phase shift can be used to determine the qubit state. We have simulated this measurement taking into the account the energy levels outside the phase qubit manifold. We have shown that, for qubit frequencies in the range of 8-12GHZ, a resonator frequency of 500 MHz and a measurement time of 100 ns, the phase difference between the two qubit states is greater than 0.2 rad. This phase difference exceeds the measurement uncertainty, and can be detected using a classical phase-meter. A fidelity of 0.9999 can be achieved for a relaxation time of 0.5 ms. We also model and simulate a microstrip-SQUID amplifier of frequency about 500 MHz, which could be used to amplify the resonator oscillations in the phase qubit adiabatic measurement. The voltage gain and the amplifier noise temperature are calculated. We simulate the preparation of a generalized Bell state and compute the relaxation times required for achieving high

  20. Theory of compressive modeling and simulation

    NASA Astrophysics Data System (ADS)

    Szu, Harold; Cha, Jae; Espinola, Richard L.; Krapels, Keith

    2013-05-01

    Modeling and Simulation (M&S) has been evolving along two general directions: (i) data-rich approach suffering the curse of dimensionality and (ii) equation-rich approach suffering computing power and turnaround time. We suggest a third approach. We call it (iii) compressive M&S (CM&S); because the basic Minimum Free-Helmholtz Energy (MFE) facilitating CM&S can reproduce and generalize Candes, Romberg, Tao & Donoho (CRT&D) Compressive Sensing (CS) paradigm as a linear Lagrange Constraint Neural network (LCNN) algorithm. CM&S based MFE can generalize LCNN to 2nd order as Nonlinear augmented LCNN. For example, during the sunset, we can avoid a reddish bias of sunlight illumination due to a long-range Rayleigh scattering over the horizon. With CM&S we can take instead of day camera, a night vision camera. We decomposed long wave infrared (LWIR) band with filter into 2 vector components (8~10μm and 10~12μm) and used LCNN to find pixel by pixel the map of Emissive-Equivalent Planck Radiation Sources (EPRS). Then, we up-shifted consistently, according to de-mixed sources map, to the sub-micron RGB color image. Moreover, the night vision imaging can also be down-shifted at Passive Millimeter Wave (PMMW) imaging, suffering less blur owing to dusty smokes scattering and enjoying apparent smoothness of surface reflectivity of man-made objects under the Rayleigh resolution. One loses three orders of magnitudes in the spatial Rayleigh resolution; but gains two orders of magnitude in the reflectivity, and gains another two orders in the propagation without obscuring smog . Since CM&S can generate missing data and hard to get dynamic transients, CM&S can reduce unnecessary measurements and their associated cost and computing in the sense of super-saving CS: measuring one & getting one's neighborhood free .

  1. On-line simulations of models for backward masking.

    PubMed

    Francis, Gregory

    2003-11-01

    Five simulations of quantitative models of visual backward masking are available on the Internet at http://www.psych.purdue.edu/-gfrancis/Publications/BackwardMasking/. The simulations can be run in a Web browser that supports the Java programming language. This article describes the motivation for making the simulations available and gives a brief introduction as to how the simulations are used. The source code is available on the Web page, and this article describes how the code is organized.

  2. Towards Automatic Processing of Virtual City Models for Simulations

    NASA Astrophysics Data System (ADS)

    Piepereit, R.; Schilling, A.; Alam, N.; Wewetzer, M.; Pries, M.; Coors, V.

    2016-10-01

    Especially in the field of numerical simulations, such as flow and acoustic simulations, the interest in using virtual 3D models to optimize urban systems is increasing. The few instances in which simulations were already carried out in practice have been associated with an extremely high manual and therefore uneconomical effort for the processing of models. Using different ways of capturing models in Geographic Information System (GIS) and Computer Aided Engineering (CAE), increases the already very high complexity of the processing. To obtain virtual 3D models suitable for simulation, we developed a tool for automatic processing with the goal to establish ties between the world of GIS and CAE. In this paper we introduce a way to use Coons surfaces for the automatic processing of building models in LoD2, and investigate ways to simplify LoD3 models in order to reduce unnecessary information for a numerical simulation.

  3. Probabilistic Based Modeling and Simulation Assessment

    DTIC Science & Technology

    2010-06-01

    with an unbelted Hybrid III model The Hybrid III dummy model was then restrained using a finite element seatbelt model. The dummy model has the...artifacts of the modeling process and not representative of the true physics of the impact, and can thus be qualified as unwanted noise in the model

  4. Integrated Modeling, Mapping, and Simulation (IMMS) framework for planning exercises.

    SciTech Connect

    Friedman-Hill, Ernest J.; Plantenga, Todd D.

    2010-06-01

    The Integrated Modeling, Mapping, and Simulation (IMMS) program is designing and prototyping a simulation and collaboration environment for linking together existing and future modeling and simulation tools to enable analysts, emergency planners, and incident managers to more effectively, economically, and rapidly prepare, analyze, train, and respond to real or potential incidents. When complete, the IMMS program will demonstrate an integrated modeling and simulation capability that supports emergency managers and responders with (1) conducting 'what-if' analyses and exercises to address preparedness, analysis, training, operations, and lessons learned, and (2) effectively, economically, and rapidly verifying response tactics, plans and procedures.

  5. Modeling and simulation of cement hydration kinetics and microstructure development

    SciTech Connect

    Thomas, Jeffrey J.; Biernacki, Joseph J.; Bullard, Jeffrey W.; Bishnoi, Shashank; Dolado, Jorge S.; Scherer, George W.; Luttge, Andreas

    2011-12-15

    Efforts to model and simulate the highly complex cement hydration process over the past 40 years are reviewed, covering different modeling approaches such as single particle models, mathematical nucleation and growth models, and vector and lattice-based approaches to simulating microstructure development. Particular attention is given to promising developments that have taken place in the past few years. Recent applications of molecular-scale simulation methods to understanding the structure and formation of calcium-silicate-hydrate phases, and to understanding the process of dissolution of cement minerals in water are also discussed, as these topics are highly relevant to the future development of more complete and fundamental hydration models.

  6. A Simulation Model Articulation of the REA Ontology

    NASA Astrophysics Data System (ADS)

    Laurier, Wim; Poels, Geert

    This paper demonstrates how the REA enterprise ontology can be used to construct simulation models for business processes, value chains and collaboration spaces in supply chains. These models support various high-level and operational management simulation applications, e.g. the analysis of enterprise sustainability and day-to-day planning. First, the basic constructs of the REA ontology and the ExSpect modelling language for simulation are introduced. Second, collaboration space, value chain and business process models and their conceptual dependencies are shown, using the ExSpect language. Third, an exhibit demonstrates the use of value chain models in predicting the financial performance of an enterprise.

  7. Automatic mathematical modeling for real time simulation program (AI application)

    NASA Technical Reports Server (NTRS)

    Wang, Caroline; Purinton, Steve

    1989-01-01

    A methodology is described for automatic mathematical modeling and generating simulation models. The major objective was to create a user friendly environment for engineers to design, maintain, and verify their models; to automatically convert the mathematical models into conventional code for computation; and finally, to document the model automatically.

  8. Logistics of Trainsets Creation with the Use of Simulation Models

    NASA Astrophysics Data System (ADS)

    Sedláček, Michal; Pavelka, Hynek

    2016-12-01

    This paper focuses on rail transport in following the train formation operational processes problem using computer simulations. The problem has been solved using SIMUL8 and applied to specific train formation station in the Czech Republic. The paper describes a proposal simulation model of the train formation work. Experimental modeling with an assessment of achievements and design solution for optimizing of the train formation operational process is also presented.

  9. Modeling and Simulation for Design of Suspended MEMS

    DTIC Science & Technology

    2003-05-21

    simulating systems with complicated electronics is limited. Exporting reduced-order models to aHDLs enables co-simulation with transistor-level...circuit-level behavioral simulation, the models are implemented in analog hardware description languages ( aHDLs ) or directly in element matrices, both...end of module The physical equations could be implemented in the aHDLs in multiple alternative ways. It has been noticed that the language

  10. Modeling and Simulation of Ceramic Arrays to Improve Ballistic Performance

    DTIC Science & Technology

    2014-01-17

    30cal AP M2 Projectile, 762x39 PS Projectile, SPH, Aluminum 5083, SiC, DoP Expeminets, AutoDyn Simulations, Tile Gap 16. SECURITY CLASSIFICATION...configurations. 1. Establish a baseline of materials properties and projectile characteristics for modeling. a. Models are developed in AUTODYN and...model. Modeling and simulation of ceramic composite systems will be performed using explicit dynamic hydrocode LS-DYNA and AUTODYN . Computational

  11. Software Requirements Specification Verifiable Fuel Cycle Simulation (VISION) Model

    SciTech Connect

    D. E. Shropshire; W. H. West

    2005-11-01

    The purpose of this Software Requirements Specification (SRS) is to define the top-level requirements for a Verifiable Fuel Cycle Simulation Model (VISION) of the Advanced Fuel Cycle (AFC). This simulation model is intended to serve a broad systems analysis and study tool applicable to work conducted as part of the AFCI (including costs estimates) and Generation IV reactor development studies.

  12. The Use of Simulation Models in Teaching Geomorphology and Hydrology.

    ERIC Educational Resources Information Center

    Kirkby, Mike; Naden, Pam

    1988-01-01

    Learning about the physical environment from computer simulation models is discussed in terms of three stages: exploration, experimentation, and calibration. Discusses the effective use of models and presents two computer simulations written in BBC BASIC, STORFLO (for catchment hydrology) and SLOPEK (for hillslope evolution). (Author/GEA)

  13. Learning-Testing Process in Classroom: An Empirical Simulation Model

    ERIC Educational Resources Information Center

    Buda, Rodolphe

    2009-01-01

    This paper presents an empirical micro-simulation model of the teaching and the testing process in the classroom (Programs and sample data are available--the actual names of pupils have been hidden). It is a non-econometric micro-simulation model describing informational behaviors of the pupils, based on the observation of the pupils'…

  14. Modeling and simulation of graphene devices

    NASA Astrophysics Data System (ADS)

    Chauhan, Jyotsna

    Graphene has been explored as one of the promising materials to sustain Moore's law especially with silicon approaching its limits. The extraordinary electronic properties of graphene like high mobility, high saturation velocity etc. have created a gold rush for graphene based electronics. The numerical study in this dissertation provides valuable insights into device physics and characteristics of graphene Field Effect Transistors (FETs). First part of dissertation studies the effect of inelastic phonon scattering in graphene FETs using semi classical approach. A kink behavior due to ambipolar transport is observed. Even the low field mobility is affected by inelastic phonon scattering in recent graphene FET experiments reporting high mobilities. Physical mechanisms for good linearity are explained. The high frequency performance limits of graphene FETs are studied by running quantum simulations. Although Klein band-to-band tunneling is significant for sub-100nm graphene FETs, it is possible to achieve a good transconductance and ballistic on-off ratio larger than 3 even at a channel length of 20nm. At a channel length of 20nm, the intrinsic cut-off frequency remains at a couple of THz for various gate insulator thickness values, but a thin gate insulator is necessary for a good transconductance and smaller degradation of cut-off frequency in the presence of parasitic capacitance. With a thin high-kappa gate insulator, the intrinsic ballistic fT is above 5THz for gate length of 10nm. The source and drain resistance severely degrade RF parameters, fMAX and f T. It is found that the intrinsic fT is close to the LC characteristic frequency set by graphene kinetic inductance and quantum capacitance. Graphene on silicon contacts are modeled. Graphene on silicon forms Schottky contact with a flexibility to tune the Schottky barrier height (SBH) by silicon doping and gate voltage. Multiple layers of graphene at the interface as well as donor type interface states reduce

  15. A Simulation and Modeling Framework for Space Situational Awareness

    SciTech Connect

    Olivier, S S

    2008-09-15

    This paper describes the development and initial demonstration of a new, integrated modeling and simulation framework, encompassing the space situational awareness enterprise, for quantitatively assessing the benefit of specific sensor systems, technologies and data analysis techniques. The framework is based on a flexible, scalable architecture to enable efficient, physics-based simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel computer systems available, for example, at Lawrence Livermore National Laboratory. The details of the modeling and simulation framework are described, including hydrodynamic models of satellite intercept and debris generation, orbital propagation algorithms, radar cross section calculations, optical brightness calculations, generic radar system models, generic optical system models, specific Space Surveillance Network models, object detection algorithms, orbit determination algorithms, and visualization tools. The use of this integrated simulation and modeling framework on a specific scenario involving space debris is demonstrated.

  16. MOVES (MOTOR VEHICLE EMISSION SIMULATOR) MODEL ...

    EPA Pesticide Factsheets

    A computer model, intended to eventually replace the MOBILE model and to incorporate the NONROAD model, that will provide the ability to estimate criteria and toxic air pollutant emission factors and emission inventories that are specific to the areas and time periods of interest, at scales ranging from local to national. Development of a new emission factor and inventory model for mobile source emissions. The model will be used by air pollution modelers within EPA, and at the State and local levels.

  17. A novel FEA simulation model for RFID SAW tag.

    PubMed

    Peng, Dasong; Yu, Fengqi

    2009-08-01

    Based on finite element analysis, we propose a simulation model for radio frequency identification (RFID) SAW tag devices. Electric properties of metal electrode on substrate greatly affect the characteristics of the device and are discussed in the paper. Then the right and left boundary conditions for the device are applied to remove large unwanted waves generated by wave propagation near the boundaries. To save computation time, a 2-D model is proposed, where some mesh skills are applied. The tag device is simulated in 2 steps. First, we use modal analysis to get the device phase velocity and harmonic frequency. Second, a tag with multireflectors is simulated. Based on the simulations, we have designed and fabricated a SAW tag. A comparison is made between simulation and experimental results and shows our simulation model agrees with the experiment very well.

  18. Aerosol kinetic code "AERFORM": Model, validation and simulation results

    NASA Astrophysics Data System (ADS)

    Gainullin, K. G.; Golubev, A. I.; Petrov, A. M.; Piskunov, V. N.

    2016-06-01

    The aerosol kinetic code "AERFORM" is modified to simulate droplet and ice particle formation in mixed clouds. The splitting method is used to calculate condensation and coagulation simultaneously. The method is calibrated with analytic solutions of kinetic equations. Condensation kinetic model is based on cloud particle growth equation, mass and heat balance equations. The coagulation kinetic model includes Brownian, turbulent and precipitation effects. The real values are used for condensation and coagulation growth of water droplets and ice particles. The model and the simulation results for two full-scale cloud experiments are presented. The simulation model and code may be used autonomously or as an element of another code.

  19. Approaches to ionospheric modelling, simulation and prediction

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Sojka, J. J.

    1992-08-01

    The ionosphere is a complex, multispecies, anisotropic medium that exhibits a significant variation with time, space, season, solar cycle, and geomagnetic activity. In recent years, a wide range of models have been developed in an effort to describe ionospheric behavior. The modeling efforts include: (1) empirical models based on extensive worldwide data sets; (2) simple analytical models for a restricted number of ionospheric parameters; (3) comprehensive, 3D, time-dependent models that require supercomputers; (4) spherical harmonic models based on fits to output obtained from comprehensive numerical models; and (5) ionospheric models driven by real-time magnetospheric inputs. In an effort to achieve simplicity, some of the models have been restricted to certain altitude or latitude domains, while others have been restricted to certain ionospheric parameters, such as the F-region peak density, the auroral conductivity, and the plasma temperatures. The current status of the modeling efforts is reviewed.

  20. ESA Simulation Language (ESL) battery model upgrade

    NASA Astrophysics Data System (ADS)

    Hay, J. L.; Owen, J. R.

    1988-03-01

    An ESL nickel-cadmium battery model was extended to match the battery manufacturer's steady state cycling characteristics, and to increase the temperature range over which the model is valid. The model was validated by comparisons with test results in the ambient temperature range 0 to 20 C. Less confidence must be attached to results produced by the model outside the 0 to 20 C range, there being no battery cycling data outside this range with which to judge model performance.

  1. Open Source Cable Models for EMI Simulations

    NASA Astrophysics Data System (ADS)

    Greedy, S.; Smartt, C.; Thomas, D. W. P.

    2016-05-01

    This paper describes the progress of work towards an Open Source software toolset suitable for developing Spice based multi-conductor cable models. The issues related to creating a transmission line model for implementation in Spice which include the frequency dependent properties of real cables are presented and the viability of spice cable models is demonstrated through application to a three conductor crosstalk model. Development of the techniques to include models of shielded cables and incident field excitation has been demonstrated.

  2. Reducing Outpatient Waiting Time: A Simulation Modeling Approach

    PubMed Central

    Aeenparast, Afsoon; Tabibi, Seyed Jamaleddin; Shahanaghi, Kamran; Aryanejhad, Mir Bahador

    2013-01-01

    Objectives The objective of this study was to provide a model for reducing outpatient waiting time by using simulation. Materials and Methods A simulation model was constructed by using the data of arrival time, service time and flow of 357 patients referred to orthopedic clinic of a general teaching hospital in Tehran. The simulation model was validated before constructing different scenarios. Results In this study 10 scenarios were presented for reducing outpatient waiting time. Patients waiting time was divided into three levels regarding their physicians. These waiting times for all scenarios were computed by simulation model. According to the final scores the 9th scenario was selected as the best way for reducing outpatient's waiting time. Conclusions Using the simulation as a decision making tool helps us to decide how we can reduce outpatient's waiting time. Comparison of outputs of this scenario and the based- case scenario in simulation model shows that combining physician's work time changing with patient's admission time changing (scenario 9) would reduce patient waiting time about 73.09%. Due to dynamic and complex nature of healthcare systems, the application of simulation for the planning, modeling and analysis of these systems has lagged behind traditional manufacturing practices. Rapid growth in health care system expenditures, technology and competition has increased the complexity of health care systems. Simulation is a useful tool for decision making in complex and probable systems. PMID:24616801

  3. Mars Exploration Rover Terminal Descent Mission Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Raiszadeh, Behzad; Queen, Eric M.

    2004-01-01

    Because of NASA's added reliance on simulation for successful interplanetary missions, the MER mission has developed a detailed EDL trajectory modeling and simulation. This paper summarizes how the MER EDL sequence of events are modeled, verification of the methods used, and the inputs. This simulation is built upon a multibody parachute trajectory simulation tool that has been developed in POST I1 that accurately simulates the trajectory of multiple vehicles in flight with interacting forces. In this model the parachute and the suspended bodies are treated as 6 Degree-of-Freedom (6 DOF) bodies. The terminal descent phase of the mission consists of several Entry, Descent, Landing (EDL) events, such as parachute deployment, heatshield separation, deployment of the lander from the backshell, deployment of the airbags, RAD firings, TIRS firings, etc. For an accurate, reliable simulation these events need to be modeled seamlessly and robustly so that the simulations will remain numerically stable during Monte-Carlo simulations. This paper also summarizes how the events have been modeled, the numerical issues, and modeling challenges.

  4. A View on Future Building System Modeling and Simulation

    SciTech Connect

    Wetter, Michael

    2011-04-01

    This chapter presents what a future environment for building system modeling and simulation may look like. As buildings continue to require increased performance and better comfort, their energy and control systems are becoming more integrated and complex. We therefore focus in this chapter on the modeling, simulation and analysis of building energy and control systems. Such systems can be classified as heterogeneous systems because they involve multiple domains, such as thermodynamics, fluid dynamics, heat and mass transfer, electrical systems, control systems and communication systems. Also, they typically involve multiple temporal and spatial scales, and their evolution can be described by coupled differential equations, discrete equations and events. Modeling and simulating such systems requires a higher level of abstraction and modularisation to manage the increased complexity compared to what is used in today's building simulation programs. Therefore, the trend towards more integrated building systems is likely to be a driving force for changing the status quo of today's building simulation programs. Thischapter discusses evolving modeling requirements and outlines a path toward a future environment for modeling and simulation of heterogeneous building systems.A range of topics that would require many additional pages of discussion has been omitted. Examples include computational fluid dynamics for air and particle flow in and around buildings, people movement, daylight simulation, uncertainty propagation and optimisation methods for building design and controls. For different discussions and perspectives on the future of building modeling and simulation, we refer to Sahlin (2000), Augenbroe (2001) and Malkawi and Augenbroe (2004).

  5. Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

    DTIC Science & Technology

    2013-07-01

    will be used in different FEA simulations. Quarter-symmetric model is used in AutoDyn to simulate DoP experiments on aluminum targets and ceramic...reference - ARL-TR-2219, 2000. 15. SUBJECT TERMS .30cal AP M2 Projectile, 762x39 PS Projectile, SPH, Aluminum 5083, SiC, DoP Expeminets, AutoDyn ...projectiles in HyperMesh which will be used in different FEA simulations. D Quarter-symmetric model is used in AutoDyn to simulate DoP experiments on

  6. Application of Hidden Markov Models in Biomolecular Simulations.

    PubMed

    Shukla, Saurabh; Shamsi, Zahra; Moffett, Alexander S; Selvam, Balaji; Shukla, Diwakar

    2017-01-01

    Hidden Markov models (HMMs) provide a framework to analyze large trajectories of biomolecular simulation datasets. HMMs decompose the conformational space of a biological molecule into finite number of states that interconvert among each other with certain rates. HMMs simplify long timescale trajectories for human comprehension, and allow comparison of simulations with experimental data. In this chapter, we provide an overview of building HMMs for analyzing bimolecular simulation datasets. We demonstrate the procedure for building a Hidden Markov model for Met-enkephalin peptide simulation dataset and compare the timescales of the process.

  7. Dynamics modeling and simulation of autonomous underwater vehicles with appendages

    NASA Astrophysics Data System (ADS)

    Su, Yumin; Zhao, Jinxin; Cao, Jian; Zhang, Guocheng

    2013-03-01

    To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle's (AUV) motion controller, a six-degree of freedom (6-DOF) dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV's motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.

  8. Modelling atmospheric turbulence for a motion-based simulator

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.; Joshi, D.

    1975-01-01

    The background information in establishing several proposed atmospheric turbulence models for use on motion based aircraft simulators was documented. A specific model was proposed which, in addition to varying turbulence intensity (rms velocity), varies the atmospheric turbulence scale length to achieve compatibility with real atmospheric turbulence. With a suitable combination of scale length and intensity distribution, the model will simulate various atmospheric conditions characterized by altitude, stability, and terrain. The model is mechanized to be included in a flight simulator experiment in order to determine to what extent the pilots are sensitive to changes in atmospheric conditions and the realism of the model. The following topics were covered: literature survey, presently used techniques, proposed model, and simulation details.

  9. Methodology of modeling and measuring computer architectures for plasma simulations

    NASA Technical Reports Server (NTRS)

    Wang, L. P. T.

    1977-01-01

    A brief introduction to plasma simulation using computers and the difficulties on currently available computers is given. Through the use of an analyzing and measuring methodology - SARA, the control flow and data flow of a particle simulation model REM2-1/2D are exemplified. After recursive refinements the total execution time may be greatly shortened and a fully parallel data flow can be obtained. From this data flow, a matched computer architecture or organization could be configured to achieve the computation bound of an application problem. A sequential type simulation model, an array/pipeline type simulation model, and a fully parallel simulation model of a code REM2-1/2D are proposed and analyzed. This methodology can be applied to other application problems which have implicitly parallel nature.

  10. Spiral Growth in Plants: Models and Simulations

    ERIC Educational Resources Information Center

    Allen, Bradford D.

    2004-01-01

    The analysis and simulation of spiral growth in plants integrates algebra and trigonometry in a botanical setting. When the ideas presented here are used in a mathematics classroom/computer lab, students can better understand how basic assumptions about plant growth lead to the golden ratio and how the use of circular functions leads to accurate…

  11. Principles for modeling and functional simulation of biological microstructures

    NASA Astrophysics Data System (ADS)

    Kriete, Andres

    1997-04-01

    This paper discusses some aspects of computer based modeling of biological microstructures. The workflow tom model and simulate a biological structure is described as a feedback- loop. Beside the system definition by structural and dynamical properties, the simulation is discussed as a mathematical representation coupled with a computer visualization. As an example, the investigation of the functional behavior of lung structures is described with special emphasis to the modeling of respiratory units.

  12. Knowledge Based Simulation: An Artificial Intelligence Approach to System Modeling and Automating the Simulation Life Cycle.

    DTIC Science & Technology

    1988-04-13

    Simulation: An Artificial Intelligence Approach to System Modeling and Automating the Simulation Life Cycle Mark S. Fox, Nizwer Husain, Malcolm...years of research in the application of Artificial Intelligence to Simulation. Our focus has been in two areas: the use of Al knowledge representation...this problem by using Artificial Intelligence (Al) knowledge representation techniques, such as frames, to represent the objects and their

  13. Methodology for characterizing modeling and discretization uncertainties in computational simulation

    SciTech Connect

    ALVIN,KENNETH F.; OBERKAMPF,WILLIAM L.; RUTHERFORD,BRIAN M.; DIEGERT,KATHLEEN V.

    2000-03-01

    This research effort focuses on methodology for quantifying the effects of model uncertainty and discretization error on computational modeling and simulation. The work is directed towards developing methodologies which treat model form assumptions within an overall framework for uncertainty quantification, for the purpose of developing estimates of total prediction uncertainty. The present effort consists of work in three areas: framework development for sources of uncertainty and error in the modeling and simulation process which impact model structure; model uncertainty assessment and propagation through Bayesian inference methods; and discretization error estimation within the context of non-deterministic analysis.

  14. Use case driven approach to develop simulation model for PCS of APR1400 simulator

    SciTech Connect

    Dong Wook, Kim; Hong Soo, Kim; Hyeon Tae, Kang; Byung Hwan, Bae

    2006-07-01

    The full-scope simulator is being developed to evaluate specific design feature and to support the iterative design and validation in the Man-Machine Interface System (MMIS) design of Advanced Power Reactor (APR) 1400. The simulator consists of process model, control logic model, and MMI for the APR1400 as well as the Power Control System (PCS). In this paper, a use case driven approach is proposed to develop a simulation model for PCS. In this approach, a system is considered from the point of view of its users. User's view of the system is based on interactions with the system and the resultant responses. In use case driven approach, we initially consider the system as a black box and look at its interactions with the users. From these interactions, use cases of the system are identified. Then the system is modeled using these use cases as functions. Lower levels expand the functionalities of each of these use cases. Hence, starting from the topmost level view of the system, we proceeded down to the lowest level (the internal view of the system). The model of the system thus developed is use case driven. This paper will introduce the functionality of the PCS simulation model, including a requirement analysis based on use case and the validation result of development of PCS model. The PCS simulation model using use case will be first used during the full-scope simulator development for nuclear power plant and will be supplied to Shin-Kori 3 and 4 plant. The use case based simulation model development can be useful for the design and implementation of simulation models. (authors)

  15. Wall-Modeled Large Eddy Simulation

    NASA Video Gallery

    This animation shows a computer modeling tool that is being used to try to make an accurate prediction of the flow around high-lift aircraft wing configurations. Being able to accurately model airf...

  16. Development of the Transport Class Model (TCM) Aircraft Simulation From a Sub-Scale Generic Transport Model (GTM) Simulation

    NASA Technical Reports Server (NTRS)

    Hueschen, Richard M.

    2011-01-01

    A six degree-of-freedom, flat-earth dynamics, non-linear, and non-proprietary aircraft simulation was developed that is representative of a generic mid-sized twin-jet transport aircraft. The simulation was developed from a non-proprietary, publicly available, subscale twin-jet transport aircraft simulation using scaling relationships and a modified aerodynamic database. The simulation has an extended aerodynamics database with aero data outside the normal transport-operating envelope (large angle-of-attack and sideslip values). The simulation has representative transport aircraft surface actuator models with variable rate-limits and generally fixed position limits. The simulation contains a generic 40,000 lb sea level thrust engine model. The engine model is a first order dynamic model with a variable time constant that changes according to simulation conditions. The simulation provides a means for interfacing a flight control system to use the simulation sensor variables and to command the surface actuators and throttle position of the engine model.

  17. Modeling Physics with Easy Java Simulations

    ERIC Educational Resources Information Center

    Christian, Wolfgang; Esquembre, Francisco

    2007-01-01

    Modeling has been shown to correct weaknesses of traditional instruction by engaging students in the design of physical models to describe, explain, and predict phenomena. Although the modeling method can be used without computers, the use of computers allows students to study problems that are difficult and time consuming, to visualize their…

  18. Optimization of Operations Resources via Discrete Event Simulation Modeling

    NASA Technical Reports Server (NTRS)

    Joshi, B.; Morris, D.; White, N.; Unal, R.

    1996-01-01

    The resource levels required for operation and support of reusable launch vehicles are typically defined through discrete event simulation modeling. Minimizing these resources constitutes an optimization problem involving discrete variables and simulation. Conventional approaches to solve such optimization problems involving integer valued decision variables are the pattern search and statistical methods. However, in a simulation environment that is characterized by search spaces of unknown topology and stochastic measures, these optimization approaches often prove inadequate. In this paper, we have explored the applicability of genetic algorithms to the simulation domain. Genetic algorithms provide a robust search strategy that does not require continuity and differentiability of the problem domain. The genetic algorithm successfully minimized the operation and support activities for a space vehicle, through a discrete event simulation model. The practical issues associated with simulation optimization, such as stochastic variables and constraints, were also taken into consideration.

  19. Evaluation of regional climate simulations for air quality modelling purposes

    NASA Astrophysics Data System (ADS)

    Menut, Laurent; Tripathi, Om P.; Colette, Augustin; Vautard, Robert; Flaounas, Emmanouil; Bessagnet, Bertrand

    2013-05-01

    In order to evaluate the future potential benefits of emission regulation on regional air quality, while taking into account the effects of climate change, off-line air quality projection simulations are driven using weather forcing taken from regional climate models. These regional models are themselves driven by simulations carried out using global climate models (GCM) and economical scenarios. Uncertainties and biases in climate models introduce an additional "climate modeling" source of uncertainty that is to be added to all other types of uncertainties in air quality modeling for policy evaluation. In this article we evaluate the changes in air quality-related weather variables induced by replacing reanalyses-forced by GCM-forced regional climate simulations. As an example we use GCM simulations carried out in the framework of the ERA-interim programme and of the CMIP5 project using the Institut Pierre-Simon Laplace climate model (IPSLcm), driving regional simulations performed in the framework of the EURO-CORDEX programme. In summer, we found compensating deficiencies acting on photochemistry: an overestimation by GCM-driven weather due to a positive bias in short-wave radiation, a negative bias in wind speed, too many stagnant episodes, and a negative temperature bias. In winter, air quality is mostly driven by dispersion, and we could not identify significant differences in either wind or planetary boundary layer height statistics between GCM-driven and reanalyses-driven regional simulations. However, precipitation appears largely overestimated in GCM-driven simulations, which could significantly affect the simulation of aerosol concentrations. The identification of these biases will help interpreting results of future air quality simulations using these data. Despite these, we conclude that the identified differences should not lead to major difficulties in using GCM-driven regional climate simulations for air quality projections.

  20. Impact of reactive settler models on simulated WWTP performance.

    PubMed

    Gernaey, K V; Jeppsson, U; Batstone, D J; Ingildsen, P

    2006-01-01

    Including a reactive settler model in a wastewater treatment plant model allows representation of the biological reactions taking place in the sludge blanket in the settler, something that is neglected in many simulation studies. The idea of including a reactive settler model is investigated for an ASM1 case study. Simulations with a whole plant model including the non-reactive Takács settler model are used as a reference, and are compared to simulation results considering two reactive settler models. The first is a return sludge model block removing oxygen and a user-defined fraction of nitrate, combined with a non-reactive Takács settler. The second is a fully reactive ASM1 Takács settler model. Simulations with the ASM1 reactive settler model predicted a 15.3% and 7.4% improvement of the simulated N removal performance, for constant (steady-state) and dynamic influent conditions respectively. The oxygen/nitrate return sludge model block predicts a 10% improvement of N removal performance under dynamic conditions, and might be the better modelling option for ASM1 plants: it is computationally more efficient and it will not overrate the importance of decay processes in the settler.

  1. An Appraisal of Coupled Climate Model Simulations

    SciTech Connect

    Sperber, K; Gleckler, P; Covey, C; Taylor, K; Bader, D; Phillips, T; Fiorino, M; Achutarao, K

    2004-02-24

    In 2002, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) proposed the concept for a state-of-the-science appraisal of climate models to be performed approximately every two years. Motivation for this idea arose from the perceived needs of the international modeling groups and the broader climate research community to document progress more frequently than provided by the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. A committee of external reviewers, which included senior researchers from four leading international modeling centers, supported the concept by stating in its review: ''The panel enthusiastically endorses the suggestion that PCMDI develop an independent appraisal of coupled model performance every 2-3 years. This would provide a useful 'mid-course' evaluation of modeling progress in the context of larger IPCC and national assessment activities, and should include both coupled and single-component model evaluations.''

  2. Predictions of Cockpit Simulator Experimental Outcome Using System Models

    NASA Technical Reports Server (NTRS)

    Sorensen, J. A.; Goka, T.

    1984-01-01

    This study involved predicting the outcome of a cockpit simulator experiment where pilots used cockpit displays of traffic information (CDTI) to establish and maintain in-trail spacing behind a lead aircraft during approach. The experiments were run on the NASA Ames Research Center multicab cockpit simulator facility. Prior to the experiments, a mathematical model of the pilot/aircraft/CDTI flight system was developed which included relative in-trail and vertical dynamics between aircraft in the approach string. This model was used to construct a digital simulation of the string dynamics including response to initial position errors. The model was then used to predict the outcome of the in-trail following cockpit simulator experiments. Outcome included performance and sensitivity to different separation criteria. The experimental results were then used to evaluate the model and its prediction accuracy. Lessons learned in this modeling and prediction study are noted.

  3. Modeling and Real-Time Simulation of UPFC

    NASA Astrophysics Data System (ADS)

    Kimura, Misao; Takahashi, Choei; Kishibe, Hideto; Miyazaki, Yasuyuki; Noro, Yasuhiro; Iio, Naotaka

    We have developed a digital real time simulator of Power Electronics Controllers, so called FACTS (Flexible AC Transmission Systems) Controllers and/or Custom Power by using MATLABTM/SIMULINKTM and dSPACETM System. This paper describes the modeling and the calculation accuracy of a UPFC (Unified Power Flow Controller) model. Hence the developed simulator operates at a large time step, in order to improve simulation accuracy, a correction processing of the switching delay is implemented into the UPFC model. Calculation accuracy of the real time UPFC model is the same level as EMTDCTM results. We confirm stable operation of the developed UPFC model with connecting a commercial real time digital simulator (RTDSTM).

  4. A Standard Kinematic Model for Flight Simulation at NASA Ames

    NASA Technical Reports Server (NTRS)

    Mcfarland, R. E.

    1975-01-01

    A standard kinematic model for aircraft simulation exists at NASA-Ames on a variety of computer systems, one of which is used to control the flight simulator for advanced aircraft (FSAA). The derivation of the kinematic model is given and various mathematical relationships are presented as a guide. These include descriptions of standardized simulation subsystems such as the atmospheric turbulence model and the generalized six-degrees-of-freedom trim routine, as well as an introduction to the emulative batch-processing system which enables this facility to optimize its real-time environment.

  5. An Open Simulation System Model for Scientific Applications

    NASA Technical Reports Server (NTRS)

    Williams, Anthony D.

    1995-01-01

    A model for a generic and open environment for running multi-code or multi-application simulations - called the open Simulation System Model (OSSM) - is proposed and defined. This model attempts to meet the requirements of complex systems like the Numerical Propulsion Simulator System (NPSS). OSSM places no restrictions on the types of applications that can be integrated at any state of its evolution. This includes applications of different disciplines, fidelities, etc. An implementation strategy is proposed that starts with a basic prototype, and evolves over time to accommodate an increasing number of applications. Potential (standard) software is also identified which may aid in the design and implementation of the system.

  6. Simulation of combined rapid gravity filtration and backwash models.

    PubMed

    Han, S J; Fitzpatrick, C S B; Wetherill, A

    2009-01-01

    Combined rapid gravity filtration and backwash models are applied to simulate filtration and backwash cycles. The simulated results from the backwash model suggest that air flow rate can be optimised to maximise particle removal efficiency in the backwash for a particular system. The simulation of combined rapid gravity filtration and backwash models suggests that efficient backwash operation is essential for maintaining the life time of a filter. However, the filter is not advised to be completely cleaned up in the backwash and the particles retained on filter grains after the backwash can be beneficial for subsequent filtration runs.

  7. Simulation on combined rapid gravity filtration and backwash models.

    PubMed

    Han, S J; Fitzpatrick, C S B; Wetherill, A

    2009-01-01

    Combined rapid gravity filtration and backwash models have been applied to simulate filtration and backwash cycles. The simulated results from the backwash model suggest that an optimum air flow rate exists to maximise particle removal efficiency in the backwash operation for a certain backwash system. The simulation of combined rapid gravity filtration and backwash models suggests that the filter should not be completely cleaned up in the backwash and a certain amount of particles retained on filter grains after backwash can be beneficial for subsequent filtration runs. This is consistent with the experimental results in the literature.

  8. Simulation modeling of outcomes and cost effectiveness.

    PubMed

    Ramsey, S D; McIntosh, M; Etzioni, R; Urban, N

    2000-08-01

    Modeling will continue to be used to address important issues in clinical practice and health policy issues that have not been adequately studied with high-quality clinical trials. The apparent ad hoc nature of models belies the methodologic rigor that is applied to create the best models in cancer prevention and care. Models have progressed from simple decision trees to extremely complex microsimulation analyses, yet all are built using a logical process based on objective evaluation of the path between intervention and outcome. The best modelers take great care to justify both the structure and content of the model and then test their assumptions using a comprehensive process of sensitivity analysis and model validation. Like clinical trials, models sometimes produce results that are later found to be invalid as other data become available. When weighing the value of models in health care decision making, it is reasonable to consider the alternatives. In the absence of data, clinical policy decisions are often based on the recommendations of expert opinion panels or on poorly defined notions of the standard of care or medical necessity. Because such decision making rarely entails the rigorous process of data collection, synthesis, and testing that is the core of well-conducted modeling, it is usually not possible for external audiences to examine the assumptions and data that were used to derive the decisions. One of the modeler's most challenging tasks is to make the structure and content of the model transparent to the intended audience. The purpose of this article is to clarify the process of modeling, so that readers of models are more knowledgeable about their uses, strengths, and limitations.

  9. Streamflow Simulations for the Mississippi River Basin Based on Ensemble Regional Climate Model Simulations

    NASA Astrophysics Data System (ADS)

    Arritt, R. W.; Jha, M.; Takle, E. S.; Gu, R.

    2004-12-01

    Ensemble simulations provide a useful tool for studying uncertainties in climate projections and for deriving probabilistic information from deterministic forecasts. Although a number of studies have examined variability within climate models, fewer have quantified the extent to which variability and uncertainty in climate simulations then propagates through impacts models. Here we evaluate the variability in simulated streamflow that result from taking the streamflow model's inputs from different members of an ensemble of simulations by a decadal-scale nested regional climate model. The regional climate model, RegCM3, simulated a domain covering the continental U.S. and most of Mexico for the period 1986-2003 using initial and lateral boundary conditions from the NCEP-DOE Reanalysis 2. Three RegCM3 realizations were created, each initialized one month apart but otherwise identical in configuration so that their collective behavior provides a measure of internal variability of the climate model. RegCM3 output for daily precipitation, temperature, and radiation were then used as input to the Soil and Water Assessment Tool (SWAT) over the upper Mississippi River basin. Seasonal and interannual variability of SWAT-predicted streamflow indicate that the internal variability of the RegCM3 climate model carries through to produce spread in simulated streamflow from SWAT.

  10. Tools for Modeling & Simulation of Molecular and Nanoelectronics Devices

    DTIC Science & Technology

    2012-06-14

    1) Tools for Modeling & Simulation of Molecular and Nanoelectronics Devices 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...parallel algorithms to allow for simulations of realistic device structures. In Phase II, these methods will be developed and will be integrated into...the integration of other simulation engines into the ATK package. This allows these codes, which are all of academic origin to date, to be driven from

  11. Evaluation of articulation simulation system using artificial maxillectomy models.

    PubMed

    Elbashti, M E; Hattori, M; Sumita, Y I; Taniguchi, H

    2015-09-01

    Acoustic evaluation is valuable for guiding the treatment of maxillofacial defects and determining the effectiveness of rehabilitation with an obturator prosthesis. Model simulations are important in terms of pre-surgical planning and pre- and post-operative speech function. This study aimed to evaluate the acoustic characteristics of voice generated by an articulation simulation system using a vocal tract model with or without artificial maxillectomy defects. More specifically, we aimed to establish a speech simulation system for maxillectomy defect models that both surgeons and maxillofacial prosthodontists can use in guiding treatment planning. Artificially simulated maxillectomy defects were prepared according to Aramany's classification (Classes I-VI) in a three-dimensional vocal tract plaster model of a subject uttering the vowel /a/. Formant and nasalance acoustic data were analysed using Computerized Speech Lab and the Nasometer, respectively. Formants and nasalance of simulated /a/ sounds were successfully detected and analysed. Values of Formants 1 and 2 for the non-defect model were 675.43 and 976.64 Hz, respectively. Median values of Formants 1 and 2 for the defect models were 634.36 and 1026.84 Hz, respectively. Nasalance was 11% in the non-defect model, whereas median nasalance was 28% in the defect models. The results suggest that an articulation simulation system can be used to help surgeons and maxillofacial prosthodontists to plan post-surgical defects that will be facilitate maxillofacial rehabilitation.

  12. COMPARISON OF RF CAVITY TRANSPORT MODELS FOR BBU SIMULATIONS

    SciTech Connect

    Ilkyoung Shin,Byung Yunn,Todd Satogata,Shahid Ahmed

    2011-03-01

    The transverse focusing effect in RF cavities plays a considerable role in beam dynamics for low-energy beamline sections and can contribute to beam breakup (BBU) instability. The purpose of this analysis is to examine RF cavity models in simulation codes which will be used for BBU experiments at Jefferson Lab and improve BBU simulation results. We review two RF cavity models in the simulation codes elegant and TDBBU (a BBU simulation code developed at Jefferson Lab). elegant can include the Rosenzweig-Serafini (R-S) model for the RF focusing effect. Whereas TDBBU uses a model from the code TRANSPORT which considers the adiabatic damping effect, but not the RF focusing effect. Quantitative comparisons are discussed for the CEBAF beamline. We also compare the R-S model with the results from numerical simulations for a CEBAF-type 5-cell superconducting cavity to validate the use of the R-S model as an improved low-energy RF cavity transport model in TDBBU. We have implemented the R-S model in TDBBU. It will improve BBU simulation results to be more matched with analytic calculations and experimental results.

  13. Analysis of a DNA simulation model through hairpin melting experiments

    PubMed Central

    Linak, Margaret C.; Dorfman, Kevin D.

    2010-01-01

    We compare the predictions of a two-bead Brownian dynamics simulation model to melting experiments of DNA hairpins with complementary AT or GC stems and noninteracting loops in buffer A. This system emphasizes the role of stacking and hydrogen bonding energies, which are characteristics of DNA, rather than backbone bending, stiffness, and excluded volume interactions, which are generic characteristics of semiflexible polymers. By comparing high throughput data on the open-close transition of various DNA hairpins to the corresponding simulation data, we (1) establish a suitable metric to compare the simulations to experiments, (2) find a conversion between the simulation and experimental temperatures, and (3) point out several limitations of the model, including the lack of G-quartets and cross stacking effects. Our approach and experimental data can be used to validate similar coarse-grained simulation models. PMID:20886965

  14. A perspective on modeling and simulation of complex dynamical systems

    NASA Astrophysics Data System (ADS)

    Åström, K. J.

    2011-09-01

    There has been an amazing development of modeling and simulation from its beginning in the 1920s, when the technology was available only at a handful of University groups who had access to a mechanical differential analyzer. Today, tools for modeling and simulation are available for every student and engineer. This paper gives a perspective on the development with particular emphasis on technology and paradigm shifts. Modeling is increasingly important for design and operation of complex natural and man-made systems. Because of the increased use of model based control such as Kalman filters and model predictive control, models are also appearing as components of feedback systems. Modeling and simulation are multidisciplinary, it is used in a wide variety of fields and their development have been strongly influenced by mathematics, numerics, computer science and computer technology.

  15. Ground Contact Model for Mars Science Laboratory Mission Simulations

    NASA Technical Reports Server (NTRS)

    Raiszadeh, Behzad; Way, David

    2012-01-01

    The Program to Optimize Simulated Trajectories II (POST 2) has been successful in simulating the flight of launch vehicles and entry bodies on earth and other planets. POST 2 has been the primary simulation tool for the Entry Descent, and Landing (EDL) phase of numerous Mars lander missions such as Mars Pathfinder in 1997, the twin Mars Exploration Rovers (MER-A and MER-B) in 2004, Mars Phoenix lander in 2007, and it is now the main trajectory simulation tool for Mars Science Laboratory (MSL) in 2012. In all previous missions, the POST 2 simulation ended before ground impact, and a tool other than POST 2 simulated landing dynamics. It would be ideal for one tool to simulate the entire EDL sequence, thus avoiding errors that could be introduced by handing off position, velocity, or other fight parameters from one simulation to the other. The desire to have one continuous end-to-end simulation was the motivation for developing the ground interaction model in POST 2. Rover landing, including the detection of the postlanding state, is a very critical part of the MSL mission, as the EDL landing sequence continues for a few seconds after landing. The method explained in this paper illustrates how a simple ground force interaction model has been added to POST 2, which allows simulation of the entire EDL from atmospheric entry through touchdown.

  16. Simulation Model of A Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen; Russell, Larry W. (Technical Monitor)

    2002-01-01

    An electronic simulation model has been developed of a ferroelectric field effect transistor (FFET). This model can be used in standard electrical circuit simulation programs to simulate the main characteristics of the FFET. The model uses a previously developed algorithm that incorporates partial polarization as a basis for the design. The model has the main characteristics of the FFET, which are the current hysterisis with different gate voltages and decay of the drain current when the gate voltage is off. The drain current has values matching actual FFET's, which were measured experimentally. The input and output resistance in the model is similar to that of the FFET. The model is valid for all frequencies below RF levels. A variety of different ferroelectric material characteristics can be modeled. The model can be used to design circuits using FFET'S with standard electrical simulation packages. The circuit can be used in designing non-volatile memory circuits and logic circuits and is compatible with all SPICE based circuit analysis programs. The model is a drop in library that integrates seamlessly into a SPICE simulation. A comparison is made between the model and experimental data measured from an actual FFET.

  17. Material Modeling for Terminal Ballistic Simulation

    DTIC Science & Technology

    1992-09-01

    and constitutive model (describing the thermo-viszo- lastic response) of the material that it contains. From the stress state, the equa ion of motion... materials . The Zerilli-Armstrong model is based on the observation that each material structure type (fcc, bcc, hcp) will have its own constitutive ...shearing rate, as would be indicated by granular ,flow theory. Each of the brittle material models which are beginning to surface in the com- putational

  18. Modeling and Simulation. I. Introduction and Guidelines.

    DTIC Science & Technology

    1986-06-30

    workstations for computer -aided-engineering are listed, and the application fsuch workstations to neural modeling is pointed out. This paper is the...done in analogous situations. While this may seem mundane advice, and even frustrat- ing, considering how fragmented the neural modeling literature is...Another limitation for neural modellers is that migrating crest cells have not formed a synaptic information network, and the understandings from dealing

  19. A simulation of water pollution model parameter estimation

    NASA Technical Reports Server (NTRS)

    Kibler, J. F.

    1976-01-01

    A parameter estimation procedure for a water pollution transport model is elaborated. A two-dimensional instantaneous-release shear-diffusion model serves as representative of a simple transport process. Pollution concentration levels are arrived at via modeling of a remote-sensing system. The remote-sensed data are simulated by adding Gaussian noise to the concentration level values generated via the transport model. Model parameters are estimated from the simulated data using a least-squares batch processor. Resolution, sensor array size, and number and location of sensor readings can be found from the accuracies of the parameter estimates.

  20. Preliminary Modeling and Simulation Study on Olfactory Cell Sensation

    SciTech Connect

    Zhou Jun; Chen Peihua; Liu Qingjun; Wang Ping; Yang Wei

    2009-05-23

    This paper introduced olfactory sensory neuron's whole-cell model with a concrete voltage-gated ionic channels and simulation. Though there are many models in olfactory sensory neuron and olfactory bulb, it remains uncertain how they express the logic of olfactory information processing. In this article, the olfactory neural network model is also introduced. This model specifies the connections among neural ensembles of the olfactory system. The simulation results of the neural network model are consistent with the observed olfactory biological characteristics such as 1/f-type power spectrum and oscillations.

  1. Modified Numerical Simulation Model of Blood Flow in Bend

    PubMed Central

    Liu, X; Zhou, X; Hao, X; Sang, X

    2015-01-01

    ABSTRACT The numerical simulation model of blood flow in bend is studied in this paper. The curvature modification is conducted for the blood flow model in bend to obtain the modified blood flow model in bend. The modified model is verified by U tube. By comparing the simulation results with the experimental results obtained by measuring the flow data in U tube, it was found that the modified blood flow model in bend can effectively improve the prediction accuracy of blood flow data affected by the curvature effect. PMID:27398727

  2. Differentiating a Finite Element Biodegradation Simulation Model for Optimal Control

    NASA Astrophysics Data System (ADS)

    Minsker, Barbara S.; Shoemaker, Christine A.

    1996-01-01

    An optimal control model for improving the design of in situ bioremediation of groundwater has been developed. The model uses a finite element biodegradation simulation model called Bio2D to find optimal pumping strategies. Analytical derivatives of the bioremediation finite element model are derived; these derivatives must be computed for the optimal control algorithm. The derivatives are complex and nonlinear; the bulk of the computational effort in solving the optimal control problem is required to calculate the derivatives. An overview of the optimal control and simulation model formulations is also given.

  3. Simulation Model Development for Icing Effects Flight Training

    NASA Technical Reports Server (NTRS)

    Barnhart, Billy P.; Dickes, Edward G.; Gingras, David R.; Ratvasky, Thomas P.

    2003-01-01

    A high-fidelity simulation model for icing effects flight training was developed from wind tunnel data for the DeHavilland DHC-6 Twin Otter aircraft. First, a flight model of the un-iced airplane was developed and then modifications were generated to model the icing conditions. The models were validated against data records from the NASA Twin Otter Icing Research flight test program with only minimal refinements being required. The goals of this program were to demonstrate the effectiveness of such a simulator for training pilots to recognize and recover from icing situations and to establish a process for modeling icing effects to be used for future training devices.

  4. Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

    DTIC Science & Technology

    2013-09-01

    SUPPLEMENTARY NOTES 14. ABSTRACT -Half-symmetric model is used in AutoDyn to simulate Depth of Penetration (DoP) experiments on aluminum targets with...tiles. 15. SUBJECT TERMS 30cal AP M2 Projectile, 762x39 PS Projectile, SPH, Aluminum 5083, SiC, DoP Expeminets, AutoDyn Simulations 16. SECURITY

  5. Design Model for Learner-Centered, Computer-Based Simulations.

    ERIC Educational Resources Information Center

    Hawley, Chandra L.; Duffy, Thomas M.

    This paper presents a model for designing computer-based simulation environments within a constructivist framework for the K-12 school setting. The following primary criteria for the development of simulations are proposed: (1) the problem needs to be authentic; (2) the cognitive demand in learning should be authentic; (3) scaffolding supports a…

  6. Computer Simulation (Microcultures): An Effective Model for Multicultural Education.

    ERIC Educational Resources Information Center

    Nelson, Jorge O.

    This paper presents a rationale for using high-fidelity computer simulation in planning for and implementing effective multicultural education strategies. Using computer simulation, educators can begin to understand and plan for the concept of cultural sensitivity in delivering instruction. The model promises to emphasize teachers' understanding…

  7. Teaching Behavioral Modeling and Simulation Techniques for Power Electronics Courses

    ERIC Educational Resources Information Center

    Abramovitz, A.

    2011-01-01

    This paper suggests a pedagogical approach to teaching the subject of behavioral modeling of switch-mode power electronics systems through simulation by general-purpose electronic circuit simulators. The methodology is oriented toward electrical engineering (EE) students at the undergraduate level, enrolled in courses such as "Power…

  8. A Social Diffusion Model with an Application on Election Simulation

    PubMed Central

    Wang, Fu-Min; Hung, San-Chuan; Kung, Perng-Hwa; Lin, Shou-De

    2014-01-01

    Issues about opinion diffusion have been studied for decades. It has so far no empirical approach to model the interflow and formation of crowd's opinion in elections due to two reasons. First, unlike the spread of information or flu, individuals have their intrinsic attitudes to election candidates in advance. Second, opinions are generally simply assumed as single values in most diffusion models. However, in this case, an opinion should represent preference toward multiple candidates. Previously done models thus may not intuitively interpret such scenario. This work is to design a diffusion model which is capable of managing the aforementioned scenario. To demonstrate the usefulness of our model, we simulate the diffusion on the network built based on a publicly available bibliography dataset. We compare the proposed model with other well-known models such as independent cascade. It turns out that our model consistently outperforms other models. We additionally investigate electoral issues with our model simulator. PMID:24995351

  9. A social diffusion model with an application on election simulation.

    PubMed

    Lou, Jing-Kai; Wang, Fu-Min; Tsai, Chin-Hua; Hung, San-Chuan; Kung, Perng-Hwa; Lin, Shou-De; Chen, Kuan-Ta; Lei, Chin-Laung

    2014-01-01

    Issues about opinion diffusion have been studied for decades. It has so far no empirical approach to model the interflow and formation of crowd's opinion in elections due to two reasons. First, unlike the spread of information or flu, individuals have their intrinsic attitudes to election candidates in advance. Second, opinions are generally simply assumed as single values in most diffusion models. However, in this case, an opinion should represent preference toward multiple candidates. Previously done models thus may not intuitively interpret such scenario. This work is to design a diffusion model which is capable of managing the aforementioned scenario. To demonstrate the usefulness of our model, we simulate the diffusion on the network built based on a publicly available bibliography dataset. We compare the proposed model with other well-known models such as independent cascade. It turns out that our model consistently outperforms other models. We additionally investigate electoral issues with our model simulator.

  10. Simulations of Accretion Disk Wind Models

    NASA Astrophysics Data System (ADS)

    Brooks, Craig L.; Yong, Suk Yee; O'Dowd, Matthew; Webster, Rachel L.; Bate, Nicholas

    2016-01-01

    The kinematics of the broad emission line region (BELR) in quasars is largely unknown, however there is strong evidence that outflows may be a key component. For example, in approximately 15% of quasars we observe broad, blue-shifted absorption features which may be ubiquitous based on line-of-sight arguments. We use a new mathematical description of an outflowing disk-wind with an initial rotational component to predict surface brightness distributions of this wind at different orientations. These surface brightness distributions will allow us to simulate gravitational microlensing of BELR light, with a view to mapping the structure and better understanding the kinematics of these flows.

  11. Graduate Level Modeling and Simulation Overview Course

    DTIC Science & Technology

    2006-03-24

    related issues 3.6 Design of experiments 3.6.1 Input data analysis 3.6.2 Length and number of runs 3.6.3 Warm up period 3.7 Output analysis 3.7.1...minutes. 4. Tactical to Practical: Segment 13. Produced by the History Channel, portion of Simulators; 15 minutes. 5. The Making of Jurassic Park...animatronics to digital effects. The History Channel videos may be ordered from http://store.aetv.com/html/home/index.jhtml and The Making of Jurassic

  12. Status of the AIAA Modeling and Simulation Format Standard

    NASA Technical Reports Server (NTRS)

    Jackson, E. Bruce; Hildreth, Bruce L.

    2008-01-01

    The current draft AIAA Standard for flight simulation models represents an on-going effort to improve the productivity of practitioners of the art of digital flight simulation (one of the original digital computer applications). This initial release provides the capability for the efficient representation and exchange of an aerodynamic model in full fidelity; the DAVE-ML format can be easily imported (with development of site-specific import tools) in an unambiguous way with automatic verification. An attractive feature of the standard is the ability to coexist with existing legacy software or tools. The draft Standard is currently limited in scope to static elements of dynamic flight simulations; however, these static elements represent the bulk of typical flight simulation mathematical models. It is already seeing application within U.S. and Australian government agencies in an effort to improve productivity and reduce model rehosting overhead. An existing tool allows import of DAVE-ML models into a popular simulation modeling and analysis tool, and other community-contributed tools and libraries can simplify the use of DAVE-ML compliant models at compile- or run-time of high-fidelity flight simulation.

  13. Proposed best practice for projects that involve modelling and simulation.

    PubMed

    M, O'Kelly; V, Anisimov; C, Campbell; S, Hamilton

    2016-11-03

    Modelling and simulation has been used in many ways when developing new treatments. To be useful and credible, it is generally agreed that modelling and simulation should be undertaken according to some kind of best practice. A number of authors have suggested elements required for best practice in modelling and simulation. Elements that have been suggested include the pre-specification of goals, assumptions, methods, and outputs. However, a project that involves modelling and simulation could be simple or complex and could be of relatively low or high importance to the project. It has been argued that the level of detail and the strictness of pre-specification should be allowed to vary, depending on the complexity and importance of the project. This best practice document does not prescribe how to develop a statistical model. Rather, it describes the elements required for the specification of a project and requires that the practitioner justify in the specification the omission of any of the elements and, in addition, justify the level of detail provided about each element. This document is an initiative of the Special Interest Group for modelling and simulation. The Special Interest Group for modelling and simulation is a body open to members of Statisticians in the Pharmaceutical Industry and the European Federation of Statisticians in the Pharmaceutical Industry. Examples of a very detailed specification and a less detailed specification are included as appendices.

  14. An Improved Modeling of Friction for Extrusion Simulations

    SciTech Connect

    Karadogan, Celalettin; Tong, Longchang; Hora, Pavel

    2007-04-07

    Realistic representation of friction is important in extrusion simulations. Purposefully designed multi-hole die aluminum extrusion experiments showed that the conventional friction models, like the Coulomb and the shear friction models, are deficient to represent the boundary phenomena that occur during aluminum extrusion. Based on the observations, phenomenological and implementational improvements are made in the friction modeling.

  15. Shock Particle Interaction - Fully Resolved Simulations and Modeling

    NASA Astrophysics Data System (ADS)

    Mehta, Yash; Neal, Chris; Jackson, Thomas L.; Balachandar, S. "Bala"; Thakur, Siddharth

    2016-11-01

    Currently there is a substantial lack of fully resolved data for shock interacting with multiple particles. In this talk we will fill this gap by presenting results of shock interaction with 1-D array and 3-D structured arrays of particles. Objectives of performing fully resolved simulations of shock propagation through packs of multiple particles are twofold, 1) To understand the complicated physical phenomena occurring during shock particle interaction, and 2) To translate the knowledge from microscale simulations in building next generation point-particle models for macroscale simulations that can better predict the motion (forces) and heat transfer for particles. We compare results from multiple particle simulations against the single particle simulations and make relevant observations. The drag history and flow field for multiple particle simulations are markedly different from those of single particle simluations, highlighting the effect of neighboring particles. We propose new models which capture this effect of neighboring particles. These models are called Pair-wise Interaction Extended Point Particle models (PIEP). Effect of multiple neighboring particles is broken down into pair-wise interactions, and these pair-wise interactions are superimposed to get the final model U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

  16. Surrogate modeling of ultrasonic simulations using data-driven methods

    NASA Astrophysics Data System (ADS)

    Du, Xiaosong; Grandin, Robert; Leifsson, Leifur

    2017-02-01

    Ultrasonic testing (UT) is used to detect internal flaws in materials and to characterize material properties. In many applications, computational simulations are an important part of the inspection-design and analysis processes. Having fast surrogate models for UT simulations is key for enabling efficient inverse analysis and model-assisted probability of detection (MAPOD). In many cases, it is impractical to perform the aforementioned tasks in a timely manner using current simulation models directly. Fast surrogate models can make these processes computationally tractable. This paper presents investigations of using surrogate modeling techniques to create fast approximate models of UT simulator responses. In particular, we propose to integrate data-driven methods (here, kriging interpolation with variable-fidelity models to construct an accurate and fast surrogate model. These techniques are investigated using test cases involving UT simulations of solid components immersed in a water bath during the inspection process. We will apply the full ultrasonic solver and the surrogate model to the detection and characterization of the flaw. The methods will be compared in terms of quality of the responses.

  17. Teaching a Model-based Climatology Using Energy Balance Simulation.

    ERIC Educational Resources Information Center

    Unwin, David

    1981-01-01

    After outlining the difficulties of teaching climatology within an undergraduate geography curriculum, the author describes and evaluates the use of a computer assisted simulation to model surface energy balance and the effects of land use changes on local climate. (AM)

  18. Using automatic programming for simulating reliability network models

    NASA Technical Reports Server (NTRS)

    Tseng, Fan T.; Schroer, Bernard J.; Zhang, S. X.; Wolfsberger, John W.

    1988-01-01

    This paper presents the development of an automatic programming system for assisting modelers of reliability networks to define problems and then automatically generate the corresponding code in the target simulation language GPSS/PC.

  19. Simulation of optical diagnostics for crystal growth: models and results

    NASA Astrophysics Data System (ADS)

    Banish, Michele R.; Clark, Rodney L.; Kathman, Alan D.; Lawson, Shelah M.

    1991-12-01

    A computer simulation of a two-color holographic interferometric (TCHI) optical system was performed using a physical (wave) optics model. This model accurately simulates propagation through time-varying, 2-D or 3-D concentration and temperature fields as a wave phenomenon. The model calculates wavefront deformations that can be used to generate fringe patterns. This simulation modeled a proposed TriGlycine sulphate TGS flight experiment by propagating through the simplified onion-like refractive index distribution of the growing crystal and calculating the recorded wavefront deformation. The phase of this wavefront was used to generate sample interferograms that map index of refraction variation. Two such fringe patterns, generated at different wavelengths, were used to extract the original temperature and concentration field characteristics within the growth chamber. This proves feasibility for this TCHI crystal growth diagnostic technique. This simulation provides feedback to the experimental design process.

  20. Modeling open boundaries in dissipative MHD simulation

    NASA Astrophysics Data System (ADS)

    Meier, E. T.; Glasser, A. H.; Lukin, V. S.; Shumlak, U.

    2012-04-01

    The truncation of large physical domains to concentrate computational resources is necessary or desirable in simulating many natural and man-made plasma phenomena. Three open boundary condition (BC) methods for such domain truncation of dissipative magnetohydrodynamics (MHD) problems are described and compared here. A novel technique, lacuna-based open boundary conditions (LOBC), is presented for applying open BC to dissipative MHD and other hyperbolic and mixed hyperbolic-parabolic systems of partial differential equations. LOBC, based on manipulating Calderon-type near-boundary sources, essentially damp hyperbolic effects in an exterior region attached to the simulation domain and apply BC appropriate for the remaining parabolic effects (if present) at the exterior region boundary. Another technique, approximate Riemann BC (ARBC), is adapted from finite volume and discontinuous Galerkin methods. In ARBC, the value of incoming flux is specified using a local, characteristic-based method. A third commonly-used open BC, zero-normal derivative BC (ZND BC), is presented for comparison. These open BC are tested in several gas dynamics and dissipative MHD problems. LOBC are found to give stable, low-reflection solutions even in the presence of strong parabolic behavior, while ARBC are stable only when hyperbolic behavior is dominant. Pros and cons of the techniques are discussed and put into context within the body of open BC research to date.

  1. Modeling and Simulation of Marine Hydrokinetic Devices

    NASA Astrophysics Data System (ADS)

    Shoele, K.; Previsic, M.

    2012-12-01

    To accurately design a wave energy conversion system, the time domain numerical model is necessary. This is due to nonlinearities in the system from different sources such as hydrodynamic forces, device dynamics, control mechanisms, and mooring lines. Combining model accuracy with efficient and fast calculation of hydrodynamic forces in time domain is challenging and time-consuming. This article describes an easy to use and unified computational framework that handles those challenges efficiently for different types of wave energy converters. The framework has been generated as a Matlab toolbox that contains the key components of a wave to wire model. It can be used for initial performance evaluation of wave energy converters as well as detailed nonlinear analysis in the time domain. The preprocessing, post-processing, and standard modeling procedure are among the unique capabilities of the toolbox that enable users to check different device concepts and optimize device performance without dealing with modeling troubles. The hydrodynamic parameters are initially computed using the three-dimensional panel method and transformed to time domain by systematic identification techniques to accelerate computation of the hydrodynamic radiation forces. The dynamics of the whole system including nonlinear viscous forces, multi-body dynamics, mooring lines, and power takeoff units is then modeled in Matlab Simulink interface. Validation of the model with experimental studies is described and the responses of different wave energy conversion systems, especially their converted power, are presented.

  2. CHARMM-GUI 10 years for biomolecular modeling and simulation.

    PubMed

    Jo, Sunhwan; Cheng, Xi; Lee, Jumin; Kim, Seonghoon; Park, Sang-Jun; Patel, Dhilon S; Beaven, Andrew H; Lee, Kyu Il; Rui, Huan; Park, Soohyung; Lee, Hui Sun; Roux, Benoît; MacKerell, Alexander D; Klauda, Jeffrey B; Qi, Yifei; Im, Wonpil

    2016-11-14

    CHARMM-GUI, http://www.charmm-gui.org, is a web-based graphical user interface that prepares complex biomolecular systems for molecular simulations. CHARMM-GUI creates input files for a number of programs including CHARMM, NAMD, GROMACS, AMBER, GENESIS, LAMMPS, Desmond, OpenMM, and CHARMM/OpenMM. Since its original development in 2006, CHARMM-GUI has been widely adopted for various purposes and now contains a number of different modules designed to set up a broad range of simulations: (1) PDB Reader & Manipulator, Glycan Reader, and Ligand Reader & Modeler for reading and modifying molecules; (2) Quick MD Simulator, Membrane Builder, Nanodisc Builder, HMMM Builder, Monolayer Builder, Micelle Builder, and Hex Phase Builder for building all-atom simulation systems in various environments; (3) PACE CG Builder and Martini Maker for building coarse-grained simulation systems; (4) DEER Facilitator and MDFF/xMDFF Utilizer for experimentally guided simulations; (5) Implicit Solvent Modeler, PBEQ-Solver, and GCMC/BD Ion Simulator for implicit solvent related calculations; (6) Ligand Binder for ligand solvation and binding free energy simulations; and (7) Drude Prepper for preparation of simulations with the CHARMM Drude polarizable force field. Recently, new modules have been integrated into CHARMM-GUI, such as Glycolipid Modeler for generation of various glycolipid structures, and LPS Modeler for generation of lipopolysaccharide structures from various Gram-negative bacteria. These new features together with existing modules are expected to facilitate advanced molecular modeling and simulation thereby leading to an improved understanding of the structure and dynamics of complex biomolecular systems. Here, we briefly review these capabilities and discuss potential future directions in the CHARMM-GUI development project. © 2016 Wiley Periodicals, Inc.

  3. Simulation of financial market via nonlinear Ising model

    NASA Astrophysics Data System (ADS)

    Ko, Bonggyun; Song, Jae Wook; Chang, Woojin

    2016-09-01

    In this research, we propose a practical method for simulating the financial return series whose distribution has a specific heaviness. We employ the Ising model for generating financial return series to be analogous to those of the real series. The similarity between real financial return series and simulated one is statistically verified based on their stylized facts including the power law behavior of tail distribution. We also suggest the scheme for setting the parameters in order to simulate the financial return series with specific tail behavior. The simulation method introduced in this paper is expected to be applied to the other financial products whose price return distribution is fat-tailed.

  4. Icing simulation: A survey of computer models and experimental facilities

    NASA Technical Reports Server (NTRS)

    Potapczuk, M. G.; Reinmann, J. J.

    1991-01-01

    A survey of the current methods for simulation of the response of an aircraft or aircraft subsystem to an icing encounter is presented. The topics discussed include a computer code modeling of aircraft icing and performance degradation, an evaluation of experimental facility simulation capabilities, and ice protection system evaluation tests in simulated icing conditions. Current research focussed on upgrading simulation fidelity of both experimental and computational methods is discussed. The need for increased understanding of the physical processes governing ice accretion, ice shedding, and iced airfoil aerodynamics is examined.

  5. Dynamics Simulation Model for Space Tethers

    NASA Technical Reports Server (NTRS)

    Levin, E. M.; Pearson, J.; Oldson, J. C.

    2006-01-01

    This document describes the development of an accurate model for the dynamics of the Momentum Exchange Electrodynamic Reboost (MXER) system. The MXER is a rotating tether about 100-km long in elliptical Earth orbit designed to catch payloads in low Earth orbit and throw them to geosynchronous orbit or to Earth escape. To ensure successful rendezvous between the MXER tip catcher and a payload, a high-fidelity model of the system dynamics is required. The model developed here quantifies the major environmental perturbations, and can predict the MXER tip position to within meters over one orbit.

  6. Statistical inference for stochastic simulation models--theory and application.

    PubMed

    Hartig, Florian; Calabrese, Justin M; Reineking, Björn; Wiegand, Thorsten; Huth, Andreas

    2011-08-01

    Statistical models are the traditional choice to test scientific theories when observations, processes or boundary conditions are subject to stochasticity. Many important systems in ecology and biology, however, are difficult to capture with statistical models. Stochastic simulation models offer an alternative, but they were hitherto associated with a major disadvantage: their likelihood functions can usually not be calculated explicitly, and thus it is difficult to couple them to well-established statistical theory such as maximum likelihood and Bayesian statistics. A number of new methods, among them Approximate Bayesian Computing and Pattern-Oriented Modelling, bypass this limitation. These methods share three main principles: aggregation of simulated and observed data via summary statistics, likelihood approximation based on the summary statistics, and efficient sampling. We discuss principles as well as advantages and caveats of these methods, and demonstrate their potential for integrating stochastic simulation models into a unified framework for statistical modelling.

  7. Software life cycle dynamic simulation model: The organizational performance submodel

    NASA Technical Reports Server (NTRS)

    Tausworthe, Robert C.

    1985-01-01

    The submodel structure of a software life cycle dynamic simulation model is described. The software process is divided into seven phases, each with product, staff, and funding flows. The model is subdivided into an organizational response submodel, a management submodel, a management influence interface, and a model analyst interface. The concentration here is on the organizational response model, which simulates the performance characteristics of a software development subject to external and internal influences. These influences emanate from two sources: the model analyst interface, which configures the model to simulate the response of an implementing organization subject to its own internal influences, and the management submodel that exerts external dynamic control over the production process. A complete characterization is given of the organizational response submodel in the form of parameterized differential equations governing product, staffing, and funding levels. The parameter values and functions are allocated to the two interfaces.

  8. Higherorder neural network group models for financial simulation.

    PubMed

    Zhang, M; Zhang, J C; Fulcher, J

    2000-04-01

    Real world financial data is often discontinuous and non-smooth. If we attempt to use neural networks to simulate such functions, then accuracy will be a problem. Neural network group models perform this function much better. Both Polynomial Higher Order Neural network Group (PHONG) and Trigonometric polynomial Higher Order Neural network Group (THONG) models are developed. These HONG models are open box, convergent models capable of approximating any kind of piecewise continuous function, to any degree of accuracy. Moreover they are capable of handling higher frequency, higher order non-linear and discontinuous data. Results obtained using a Higher Order Neural network Group financial simulator are presented, which confirm that HONG group models converge without difficulty, and are considerably more accurate than neural network models (more specifically, around twice as good for prediction, and a factor of four improvement in the case of simulation).

  9. Improved Collision Modeling for Direct Simulation Monte Carlo Methods

    DTIC Science & Technology

    2011-03-01

    number is a measure of the rarefaction of a gas , and will be explained more thoroughly in the following chap- ter. Continuum solvers that use Navier...Limits on Mathematical Models [4] Kn=0.1, and the flow can be considered rarefied above that value. Direct Simulation Monte Carlo (DSMC) is a stochastic...method which utilizes the Monte Carlo statistical model to simulate gas behavior, which is very useful for these rarefied atmosphere hypersonic

  10. Federated Modelling and Simulation for Critical Infrastructure Protection

    NASA Astrophysics Data System (ADS)

    Rome, Erich; Langeslag, Peter; Usov, Andrij

    Modelling and simulation is an important tool for Critical Infrastructure (CI) dependency analysis, for testing methods for risk reduction, and as well for the evaluation of past failures. Moreover, interaction of such simulations with external threat models, e.g., a river flood model, or economic models enable consequence analysis and thus may assist in what-if decision-making processes. The simulation of complex scenarios involving several different CI sectors requires the usage of heterogeneous federated simulations of CIs. However, common standards for modelling and interoperability of such federated CI simulations are missing. Also, creating the required abstract models from CIs and other data, setting up the individual federate simulators and integrating all subsystems is a time-consuming and complicated task that requires substantial know-how and resources. In this chapter, we outline applications and benefit of federated modelling, simulation and analysis (MS&A) for Critical Infrastructure Protection (CIP). We review the state of the art in federated MS&A for CIP and categorise common approaches and interoperability concepts like central and lateral coupling of simulators. As examples for the latter two concepts, we will present in more detail an interoperability standard from the military domain, HLA, and an approach developed in the DIESIS project. Special emphasis will also be put on describing the problem of synchronising systems with different time models. Also, we will briefly assess the state of transferring MS&A for CIP research results to practical application by comparing the situations in the USA and in Europe.

  11. Fundamentals of chemistry modeling applicable to a vectorized particle simulation

    NASA Technical Reports Server (NTRS)

    Haas, Brian L.

    1990-01-01

    This paper describes the fundamentals of extending the vectorized particle simulation method derived by Baganoff and McDonald (1990), McDonald and Baganoff (1988), and McDonald (1989) for modeling chemically reacting flows. Details of reaction mechanics per reaction are presented, with particular attention given to the quantum nature of the vibrational mode. The models of reactive flows developed here were verified through a simulation of a superheated diatomic gas relaxing thermochemically to equilibrium in a reservoir.

  12. Visual performance modeling in the human operator simulator

    NASA Technical Reports Server (NTRS)

    Strieb, M. I.

    1979-01-01

    A brief description of the history of the development of the human operator simulator (HOS) model is presented. Features of the HOS micromodels that impact on the obtainment of visual performance data are discussed along with preliminary details on a HOS pilot model designed to predict the results of visual performance workload data obtained through oculometer studies on pilots in real and simulated approaches and landings.

  13. NASA Standard for Models and Simulations: Philosophy and Requirements Overview

    NASA Technical Reports Server (NTRS)

    Blattnig, St3eve R.; Luckring, James M.; Morrison, Joseph H.; Sylvester, Andre J.; Tripathi, Ram K.; Zang, Thomas A.

    2009-01-01

    Following the Columbia Accident Investigation Board report, the NASA Administrator chartered an executive team (known as the Diaz Team) to identify those CAIB report elements with NASA-wide applicability and to develop corrective measures to address each element. One such measure was the development of a standard for the development, documentation, and operation of models and simulations. This report describes the philosophy and requirements overview of the resulting NASA Standard for Models and Simulations.

  14. NASA Standard for Models and Simulations: Philosophy and Requirements Overview

    NASA Technical Reports Server (NTRS)

    Blattnig, Steve R.; Luckring, James M.; Morrison, Joseph H.; Sylvester, Andre J.; Tripathi, Ram K.; Zang, Thomas A.

    2013-01-01

    Following the Columbia Accident Investigation Board report, the NASA Administrator chartered an executive team (known as the Diaz Team) to identify those CAIB report elements with NASA-wide applicability and to develop corrective measures to address each element. One such measure was the development of a standard for the development, documentation, and operation of models and simulations. This report describes the philosophy and requirements overview of the resulting NASA Standard for Models and Simulations.

  15. [Research advances in soil nitrogen cycling models and their simulation].

    PubMed

    Tang, Guoyong; Huang, Daoyou; Tong, Chengli; Zhang, Wenju; Wu, Jinshui

    2005-11-01

    Nitrogen is one of the necessary nutrients for plant, and also a primary element leading to environmental pollution. Many researches have been concerned about the contribution of agricultural activities to environmental pollution by nitrogenous compounds, and the focus is how to simulate soil nitrogen cycling processes correctly. In this paper, the primary soil nitrogen cycling processes were reviewed in brief, with 13 cycling models and 6 simulated cycling processes introduced, and the parameterization of models discussed.

  16. Towards a Credibility Assessment of Models and Simulations

    NASA Technical Reports Server (NTRS)

    Blattnig, Steve R.; Green, Lawrence L.; Luckring, James M.; Morrison, Joseph H.; Tripathi, Ram K.; Zang, Thomas A.

    2008-01-01

    A scale is presented to evaluate the rigor of modeling and simulation (M&S) practices for the purpose of supporting a credibility assessment of the M&S results. The scale distinguishes required and achieved levels of rigor for a set of M&S elements that contribute to credibility including both technical and process measures. The work has its origins in an interest within NASA to include a Credibility Assessment Scale in development of a NASA standard for models and simulations.

  17. Modeling and Simulation for Safeguards and Nonproliferation Workshop

    SciTech Connect

    Gilligan, Kimberly V.; Kirk, Bernadette Lugue

    2015-01-01

    The Modeling and Simulation for Safeguards and Nonproliferation Workshop was held December 15–18, 2014, at Oak Ridge National Laboratory. This workshop was made possible by the Next Generation Safeguards Initiative Human Capital Development (NGSI HCD) Program. The idea of the workshop was to move beyond the tried-and-true boot camp training of nonproliferation concepts to spend several days on the unique perspective of applying modeling and simulation (M&S) solutions to safeguards challenges.

  18. Assessing Model Data Fit of Unidimensional Item Response Theory Models in Simulated Data

    ERIC Educational Resources Information Center

    Kose, Ibrahim Alper

    2014-01-01

    The purpose of this paper is to give an example of how to assess the model-data fit of unidimensional IRT models in simulated data. Also, the present research aims to explain the importance of fit and the consequences of misfit by using simulated data sets. Responses of 1000 examinees to a dichotomously scoring 20 item test were simulated with 25…

  19. Network Modeling and Simulation Environment (NEMSE)

    DTIC Science & Technology

    2012-07-01

    Loop Using OPNET Modeler Demo ................................................ 3 3.2.3 COPE Demo...11 B 4.3 OPNET ...13 Figure 15: Antenna Pattern in OpNet ............................................................................... 13 Figure 16: NEMSE Box

  20. Adaptive Modeling and Real-Time Simulation

    DTIC Science & Technology

    1984-01-01

    34 Artificial Inteligence , Vol. 13, pp. 27-39 (1980). Describes circumscription which is just the assumption that everything that is known to have a particular... Artificial Intelligence Truth Maintenance Planning Resolution Modeling Wcrld Models ~ .. ~2.. ASSTR AT (Coninue n evrse sieIf necesaran Identfy by...represents a marriage of (1) the procedural-network st, planning technology developed in artificial intelligence with (2) the PERT/CPM technology developed in

  1. Development and application of an atmospheric turbulence model for use in flight simulators in flight simulators

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.; Joshi, D. S.

    1976-01-01

    The influence of simulated turbulence on aircraft handling qualities was investigated. Pilot opinion of the handling qualities of a light general aviation aircraft were evaluated in a motion-base simulator using a simulated turbulence environment. A realistic representation of turbulence disturbances is described in terms of rms intensity and scale length and their random variations with time. The time histories generated by the proposed turbulence models showed characteristics which appear to be more similar to real turbulence than the frequently-used Gaussian turbulence model. In addition, the proposed turbulence models can flexibly accommodate changes in atmospheric conditions and be easily implemented in flight simulator studies. Six turbulence time histories, including the conventional Gaussian model, were used in an IFR-tracking task. The realism of each of the turbulence models and the handling qualities of the simulated airplane were evaluated. Analysis of pilot opinions shows that at approximately the same rms intensities of turbulence, the handling quality ratings transit from the satisfactory level, for the simple Gaussian model, to an unacceptable level for more realistic and compositely structured turbulence models.

  2. DSD - A Particle Simulation Code for Modeling Dusty Plasmas

    NASA Astrophysics Data System (ADS)

    Joyce, Glenn; Lampe, Martin; Ganguli, Gurudas

    1999-11-01

    The NRL Dynamically Shielded Dust code (DSD) is a particle simulation code developed to study the behavior of strongly coupled, dusty plasmas. The model includes the electrostatic wake effects of plasma ions flowing through plasma electrons, collisions of dust and plasma particles with each other and with neutrals. The simulation model contains the short-range strong forces of a shielded Coulomb system, and the long-range forces that are caused by the wake. It also includes other effects of a flowing plasma such as drag forces. In order to model strongly coupled dust in plasmas, we make use of the techniques of molecular dynamics simulation, PIC simulation, and the "particle-particle/particle-mesh" (P3M) technique of Hockney and Eastwood. We also make use of the dressed test particle representation of Rostoker and Rosenbluth. Many of the techniques we use in the model are common to all PIC plasma simulation codes. The unique properties of the code follow from the accurate representation of both the short-range aspects of the interaction between dust grains, and long-range forces mediated by the complete plasma dielectric response. If the streaming velocity is zero, the potential used in the model reduces to the Debye-Huckel potential, and the simulation is identical to molecular dynamics models of the Yukawa potential. The plasma appears only implicitly through the plasma dispersion function, so it is not necessary in the code to resolve the fast plasma time scales.

  3. Computer model to simulate testing at the National Transonic Facility

    NASA Technical Reports Server (NTRS)

    Mineck, Raymond E.; Owens, Lewis R., Jr.; Wahls, Richard A.; Hannon, Judith A.

    1995-01-01

    A computer model has been developed to simulate the processes involved in the operation of the National Transonic Facility (NTF), a large cryogenic wind tunnel at the Langley Research Center. The simulation was verified by comparing the simulated results with previously acquired data from three experimental wind tunnel test programs in the NTF. The comparisons suggest that the computer model simulates reasonably well the processes that determine the liquid nitrogen (LN2) consumption, electrical consumption, fan-on time, and the test time required to complete a test plan at the NTF. From these limited comparisons, it appears that the results from the simulation model are generally within about 10 percent of the actual NTF test results. The use of actual data acquisition times in the simulation produced better estimates of the LN2 usage, as expected. Additional comparisons are needed to refine the model constants. The model will typically produce optimistic results since the times and rates included in the model are typically the optimum values. Any deviation from the optimum values will lead to longer times or increased LN2 and electrical consumption for the proposed test plan. Computer code operating instructions and listings of sample input and output files have been included.

  4. Abdominal surgery process modeling framework for simulation using spreadsheets.

    PubMed

    Boshkoska, Biljana Mileva; Damij, Talib; Jelenc, Franc; Damij, Nadja

    2015-08-01

    We provide a continuation of the existing Activity Table Modeling methodology with a modular spreadsheets simulation. The simulation model developed is comprised of 28 modeling elements for the abdominal surgery cycle process. The simulation of a two-week patient flow in an abdominal clinic with 75 beds demonstrates the applicability of the methodology. The simulation does not include macros, thus programming experience is not essential for replication or upgrading the model. Unlike the existing methods, the proposed solution employs a modular approach for modeling the activities that ensures better readability, the possibility of easily upgrading the model with other activities, and its easy extension and connectives with other similar models. We propose a first-in-first-served approach for simulation of servicing multiple patients. The uncertain time duration of the activities is modeled using the function "rand()". The patients movements from one activity to the next one is tracked with nested "if()" functions, thus allowing easy re-creation of the process without the need of complex programming.

  5. Regional climate simulations over Vietnam using the WRF model

    NASA Astrophysics Data System (ADS)

    Raghavan, S. V.; Vu, M. T.; Liong, S. Y.

    2016-10-01

    We present an analysis of the present-day (1961-1990) regional climate simulations over Vietnam. The regional climate model Weather Research and Forecasting (WRF) was driven by the global reanalysis ERA40. The performance of the regional climate model in simulating the observed climate is evaluated with a main focus on precipitation and temperature. The regional climate model was able to reproduce the observed spatial patterns of the climate, although with some biases. The model also performed better in reproducing the extreme precipitation and the interannual variability. Overall, the WRF model was able to simulate the main regional signatures of climate variables, seasonal cycles, and frequency distributions. This study is an evaluation of the present-day climate simulations of a regional climate model at a resolution of 25 km. Given that dynamical downscaling has become common for studying climate change and its impacts, the study highlights that much more improvements in modeling might be necessary to yield realistic simulations of climate at high resolutions before they can be used for impact studies at a local scale. The need for a dense network of observations is also realized as observations at high resolutions are needed when it comes to evaluations and validations of models at sub-regional and local scales.

  6. Numerical Simulation of SNCR Technology with Simplified Chemical Kinetics Model

    NASA Astrophysics Data System (ADS)

    Blejchař, T.; Dolníčková, D.

    2013-04-01

    The paper deals with numerical simulation of SNCR method. For numerical modelling was used CFD code Ansys/CFX. SNCR method was described by dominant chemical reaction, which were look up NIST Chemical database. The reactions including reduction of NOx and concentration change of pollutants, like N2O and CO in flue gas too. Proposed chemical kinetics and CFD model was applied to two boilers. Both simulations were compared with experimental measurements. First simulation was used to validation of chemical mechanism. Second simulation was based on first simulation and it was used to verification of compiled SNCR chemical mechanism. Next the new variant of the reagent penetration lance was proposed and compared with the original variants.

  7. Numerical Modeling Studies of Wake Vortices: Real Case Simulations

    NASA Technical Reports Server (NTRS)

    Shen, Shao-Hua; Ding, Feng; Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Proctor, Fred H.

    1999-01-01

    A three-dimensional large-eddy simulation model, TASS, is used to simulate the behavior of aircraft wake vortices in a real atmosphere. The purpose for this study is to validate the use of TASS for simulating the decay and transport of wake vortices. Three simulations are performed and the results are compared with the observed data from the 1994-1995 Memphis field experiments. The selected cases have an atmospheric environment of weak turbulence and stable stratification. The model simulations are initialized with appropriate meteorological conditions and a post roll-up vortex system. The behavior of wake vortices as they descend within the atmospheric boundary layer and interact with the ground is discussed.

  8. Tools and Equipment Modeling for Automobile Interactive Assembling Operating Simulation

    SciTech Connect

    Wu Dianliang; Zhu Hongmin

    2010-05-21

    Tools and equipment play an important role in the simulation of virtual assembly, especially in the assembly process simulation and plan. Because of variety in function and complexity in structure and manipulation, the simulation of tools and equipments remains to be a challenge for interactive assembly operation. Based on analysis of details and characteristics of interactive operations for automobile assembly, the functional requirement for tools and equipments of automobile assembly is given. Then, a unified modeling method for information expression and function realization of general tools and equipments is represented, and the handling methods of manual, semi-automatic, automatic tools and equipments are discussed. Finally, the application in assembly simulation of rear suspension and front suspension of Roewe 750 automobile is given. The result shows that the modeling and handling methods are applicable in the interactive simulation of various tools and equipments, and can also be used for supporting assembly process planning in virtual environment.

  9. Modeling and simulation for space medicine operations: preliminary requirements considered

    NASA Technical Reports Server (NTRS)

    Dawson, D. L.; Billica, R. D.; McDonald, P. V.

    2001-01-01

    The NASA Space Medicine program is now developing plans for more extensive use of high-fidelity medical simulation systems. The use of simulation is seen as means to more effectively use the limited time available for astronaut medical training. Training systems should be adaptable for use in a variety of training environments, including classrooms or laboratories, space vehicle mockups, analog environments, and in microgravity. Modeling and simulation can also provide the space medicine development program a mechanism for evaluation of other medical technologies under operationally realistic conditions. Systems and procedures need preflight verification with ground-based testing. Traditionally, component testing has been accomplished, but practical means for "human in the loop" verification of patient care systems have been lacking. Medical modeling and simulation technology offer potential means to accomplish such validation work. Initial considerations in the development of functional requirements and design standards for simulation systems for space medicine are discussed.

  10. Rapid Automated Aircraft Simulation Model Updating from Flight Data

    NASA Technical Reports Server (NTRS)

    Brian, Geoff; Morelli, Eugene A.

    2011-01-01

    Techniques to identify aircraft aerodynamic characteristics from flight measurements and compute corrections to an existing simulation model of a research aircraft were investigated. The purpose of the research was to develop a process enabling rapid automated updating of aircraft simulation models using flight data and apply this capability to all flight regimes, including flight envelope extremes. The process presented has the potential to improve the efficiency of envelope expansion flight testing, revision of control system properties, and the development of high-fidelity simulators for pilot training.

  11. Kriging-approximation simulated annealing algorithm for groundwater modeling

    NASA Astrophysics Data System (ADS)

    Shen, C. H.

    2015-12-01

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

  12. Simulation model for a seven-phase BLDCM drive system

    NASA Astrophysics Data System (ADS)

    Park, Sang-Hoon; Lee, Won-Cheol; Lee, Jung-Hyo; Yu, Jae-Sung; Kim, Gyu-Sik; Won, Chung-Yuen

    2007-12-01

    BLDC motors have many advantages over brushed DC motors and induction motors. So, BLDC motors extend their application to many industrial fields. In this paper, the digital simulation and modeling of a 7-phase brushless DC motor have been presented. The 14-switch inverter and a 7-phase brushless DC motor drive system are simulated using hysteresis current controller and logic of switching pattern with the Boolean¡s function. Through some simulations, we found that our modeling and analysis of a 7-phase BLDCM with PWM inverter would be helpful for the further studies of the multi-phase BLDCM drive systems.

  13. Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

    DTIC Science & Technology

    2013-09-09

    SUPPLEMENTARY NOTES 14. ABSTRACT -Quarter-symmetric model is used in AutoDyn to simulate DoP experiments on aluminum targets and ceramic-faced aluminum... AutoDyn Simulations 16. SECURITY CLASSIFICATION OF: UU a. REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 27 19a...University of Delaware MONTHLY REPORT FOR AUGUST 2013 □ Quarter-symmetric model is used in AutoDyn to simulate DoP experiments on aluminum targets

  14. Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

    DTIC Science & Technology

    2013-11-01

    Unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Half-symmetric model is used in AutoDyn to simulate Depth of Penetration (DoP) experiments on SiC...AP M2 Projectile, 762x39 PS Projectile, SPH, Aluminum 5083, SiC, DoP Expeminets, AutoDyn Simulations, Tile Gap 16. SECURITY CLASSIFICATION OF: UU...PERFORMANCE 2013 © University of Delaware MONTHLY REPORT FOR OCTOBER 2013 □ Half-symmetric model is used in AutoDyn to simulate Depth of

  15. Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

    DTIC Science & Technology

    2013-10-01

    Unlimited. \\ \\ 13. SUPPLEMENTARY NOTES 14. ABSTRACT Half-symmetric model is used in AutoDyn to simulate Depth of Penetration (DoP) experiments on...TERMS ,30cal AP M2 Projectile, 762x39 PS Projectile, SPH, Aluminum 5083, SiC, DoP Expeminets, AutoDyn Simulations, Tile Gap 16. SECURITY...PERFORMANCE 2013 © University of Delaware MONTHLY REPORT FOR OCTOBER 2013 □ Half-symmetric model is used in AutoDyn to simulate Depth of

  16. Construction of Simulation Model for OTEC Plant Using Uehara Cycle

    NASA Astrophysics Data System (ADS)

    Goto, Satoru; Motoshima, Yoshiki; Sugi, Takenao; Yasunaga, Takeshi; Ikegami, Yasuyuki; Nakamura, Masatoshi

    Ocean Thermal Energy Conversion (OTEC) converts heat energy into electricity using 20-27[°C] temperature difference between warm seawater at surface and cold seawater in depth. In this paper, a simulation model for an OTEC plant, which uses the Uehara cycle with an ammonia-water mixture as working fluid, is constructed based on the mass balance and the heat balance. Moreover, a method of the initial value determination for numerical simulation is developed. Accuracy of the simulation model was evaluated by comparing with the experimental results of a pilot OTEC plant.

  17. Surrogate population models for large-scale neural simulations.

    PubMed

    Tripp, Bryan P

    2015-06-01

    Because different parts of the brain have rich interconnections, it is not possible to model small parts realistically in isolation. However, it is also impractical to simulate large neural systems in detail. This article outlines a new approach to multiscale modeling of neural systems that involves constructing efficient surrogate models of populations. Given a population of neuron models with correlated activity and with specific, nonrandom connections, a surrogate model is constructed in order to approximate the aggregate outputs of the population. The surrogate model requires less computation than the neural model, but it has a clear and specific relationship with the neural model. For example, approximate spike rasters for specific neurons can be derived from a simulation of the surrogate model. This article deals specifically with neural engineering framework (NEF) circuits of leaky-integrate-and-fire point neurons. Weighted sums of spikes are modeled by interpolating over latent variables in the population activity, and linear filters operate on gaussian random variables to approximate spike-related fluctuations. It is found that the surrogate models can often closely approximate network behavior with orders-of-magnitude reduction in computational demands, although there are certain systematic differences between the spiking and surrogate models. Since individual spikes are not modeled, some simulations can be performed with much longer steps sizes (e.g., 20 ms). Possible extensions to non-NEF networks and to more complex neuron models are discussed.

  18. SpaceNet: Modeling and Simulating Space Logistics

    NASA Technical Reports Server (NTRS)

    Lee, Gene; Jordan, Elizabeth; Shishko, Robert; de Weck, Olivier; Armar, Nii; Siddiqi, Afreen

    2008-01-01

    This paper summarizes the current state of the art in interplanetary supply chain modeling and discusses SpaceNet as one particular method and tool to address space logistics modeling and simulation challenges. Fundamental upgrades to the interplanetary supply chain framework such as process groups, nested elements, and cargo sharing, enabled SpaceNet to model an integrated set of missions as a campaign. The capabilities and uses of SpaceNet are demonstrated by a step-by-step modeling and simulation of a lunar campaign.

  19. Evolutionary Development of the Simulation by Logical Modeling System (SIBYL)

    NASA Technical Reports Server (NTRS)

    Wu, Helen

    1995-01-01

    Through the evolutionary development of the Simulation by Logical Modeling System (SIBYL) we have re-engineered the expensive and complex IBM mainframe based Long-term Hardware Projection Model (LHPM) to a robust cost-effective computer based mode that is easy to use. We achieved significant cost reductions and improved productivity in preparing long-term forecasts of Space Shuttle Main Engine (SSME) hardware. The LHPM for the SSME is a stochastic simulation model that projects the hardware requirements over 10 years. SIBYL is now the primary modeling tool for developing SSME logistics proposals and Program Operating Plan (POP) for NASA and divisional marketing studies.

  20. Model consistency in large eddy simulation of turbulent channel flows

    NASA Technical Reports Server (NTRS)

    Piomelli, Ugo; Ferziger, Joel H.; Moin, Parviz

    1988-01-01

    Combinations of filters and subgrid scale stress models for large eddy simulation of the Navier-Stokes equations are examined by a priori tests and numerical simulations. The structure of the subgrid scales is found to depend strongly on the type of filter used, and consistency between model and filter is essential to ensure accurate results. The implementation of consistent combinations of filter and model gives more accurate turbulence statistics than those obtained in previous investigations in which the models were chosen independently from the filter. Results and limitations of the a priori test are discussed. The effect of grid refinement is also examined.

  1. Managing health care decisions and improvement through simulation modeling.

    PubMed

    Forsberg, Helena Hvitfeldt; Aronsson, Håkan; Keller, Christina; Lindblad, Staffan

    2011-01-01

    Simulation modeling is a way to test changes in a computerized environment to give ideas for improvements before implementation. This article reviews research literature on simulation modeling as support for health care decision making. The aim is to investigate the experience and potential value of such decision support and quality of articles retrieved. A literature search was conducted, and the selection criteria yielded 59 articles derived from diverse applications and methods. Most met the stated research-quality criteria. This review identified how simulation can facilitate decision making and that it may induce learning. Furthermore, simulation offers immediate feedback about proposed changes, allows analysis of scenarios, and promotes communication on building a shared system view and understanding of how a complex system works. However, only 14 of the 59 articles reported on implementation experiences, including how decision making was supported. On the basis of these articles, we proposed steps essential for the success of simulation projects, not just in the computer, but also in clinical reality. We also presented a novel concept combining simulation modeling with the established plan-do-study-act cycle for improvement. Future scientific inquiries concerning implementation, impact, and the value for health care management are needed to realize the full potential of simulation modeling.

  2. Modeling and simulation of HTS cables for scattering parameter analysis

    NASA Astrophysics Data System (ADS)

    Bang, Su Sik; Lee, Geon Seok; Kwon, Gu-Young; Lee, Yeong Ho; Chang, Seung Jin; Lee, Chun-Kwon; Sohn, Songho; Park, Kijun; Shin, Yong-June

    2016-11-01

    Most of modeling and simulation of high temperature superconducting (HTS) cables are inadequate for high frequency analysis since focus of the simulation's frequency is fundamental frequency of the power grid, which does not reflect transient characteristic. However, high frequency analysis is essential process to research the HTS cables transient for protection and diagnosis of the HTS cables. Thus, this paper proposes a new approach for modeling and simulation of HTS cables to derive the scattering parameter (S-parameter), an effective high frequency analysis, for transient wave propagation characteristics in high frequency range. The parameters sweeping method is used to validate the simulation results to the measured data given by a network analyzer (NA). This paper also presents the effects of the cable-to-NA connector in order to minimize the error between the simulated and the measured data under ambient and superconductive conditions. Based on the proposed modeling and simulation technique, S-parameters of long-distance HTS cables can be accurately derived in wide range of frequency. The results of proposed modeling and simulation can yield the characteristics of the HTS cables and will contribute to analyze the HTS cables.

  3. Comprehensive Mathematical Model for Simulating Electroslag Remelting

    NASA Astrophysics Data System (ADS)

    Dong, Yan-Wu; Jiang, Zhou-Hua; Fan, Jin-Xi; Cao, Yu-Long; Hou, Dong; Cao, Hai-Bo

    2016-04-01

    Droplet formation and departure from an electrode tip affect the temperature distribution in liquid slag and a molten steel pool, as well as the removal of nonmetallic inclusions in the electroslag remelting process. In this article, magneto-hydrodynamics modules coupled with a volume of fluid (VOF) model (as described in VOF model theory) for tracking phase distribution have been employed to develop the electrode fusion model and to investigate formation and departure of a droplet from the electrode tip. Subsequently, the remelting rate and molten steel pool have been achieved based on the electrode fusion model. Results indicate that a droplet can increase the flow rate of liquid slag, especially the region of droplet fall through the slag pool; yet it has little impact on the flow distribution. Asymmetric flow can take place in a slag pool due to the action of the droplet. The depth of the molten steel pool increases in the presence of droplets, but the width of the mushy zone decreases. In addition, the shape of the electrode tip is not constant but changes with its fusion. The remelting rate is calculated instead of being imposed in this work. The development of the model supports further understanding of the process and the ability to set the appropriate operating parameters, especially for expensive and easy segregation materials.

  4. Assessment of simulation-based calibration of rectangular pulse models

    NASA Astrophysics Data System (ADS)

    Vanhaute, Willem Jan; Vandenberghe, Sander; Willems, Patrick; Verhoest, Niko E. C.

    2013-04-01

    The use of stochastic rainfall models has become widespread in many hydrologic applications, especially when historical rainfall records lack in length or quality to be used for practical purposes. Among a variety of models, rectangular pulse models such as the Neyman-scott and Bartlett-Lewis type models are known for their parsimonious nature and relative ease in simulating long rainfall time series. The aforementioned models are often calibrated using the generalized method of moments which fits modeled to observed moments. To ease the computational burden, the expected values of the modeled moments are usually expressed in function of the model parameters through analytical expressions. The derivation of such analytical expressions is considered to be an important bottleneck in the development of these rectangular pulse models. Any adjustment to the model structure must be accompanied by an adjustment of the analytical moments in order to be able to calibrate the adjusted model. To avoid the use of analytical moments during calibration, a simulation-based calibration is needed. The latter would enable the modeler to make and validate adjustments in a more organic matter. However, such simulation-based calibration must be able to account for the randomness of the simulation. As such, ensemble runs must be made for every objective function evaluation, resulting in considerable computational requirements. The presented research investigates how to exploit today's available computational resources in order to enable simulation-based calibration. Once such type of calibration is feasible, it will open doors to implementing adjustments to the model structure (such as the introduction of dependencies between model variables by using copulas) without the need to rely on analytical expressions of the different moments.

  5. Off-gas Adsorption Model and Simulation - OSPREY

    SciTech Connect

    Veronica J Rutledge

    2013-10-01

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes is expected to provide substantial cost savings and many technical benefits. To support this capability, a modeling effort focused on the off-gas treatment system of a used nuclear fuel recycling facility is in progress. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and REcoverY (OSPREY) models the adsorption of offgas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas composition, sorbent and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data can be obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. In addition to concentration data, the model predicts temperature along the column length as a function of time and pressure drop along the column length. A description of the OSPREY model, results from krypton adsorption modeling and plans for modeling the behavior of iodine, xenon, and tritium will be discussed.

  6. Cooperative global security programs modeling & simulation.

    SciTech Connect

    Briand, Daniel

    2010-05-01

    The national laboratories global security programs implement sustainable technical solutions for cooperative nonproliferation, arms control, and physical security systems worldwide. To help in the development and execution of these programs, a wide range of analytical tools are used to model, for example, synthetic tactical environments for assessing infrastructure protection initiatives and tactics, systematic approaches for prioritizing nuclear and biological threat reduction opportunities worldwide, and nuclear fuel cycle enrichment and spent fuel management for nuclear power countries. This presentation will describe how these models are used in analyses to support the Obama Administration's agenda and bilateral/multinational treaties, and ultimately, to reduce weapons of mass destruction and terrorism threats through international technical cooperation.

  7. Comparison of simulator fidelity model predictions with in-simulator evaluation data

    NASA Technical Reports Server (NTRS)

    Parrish, R. V.; Mckissick, B. T.; Ashworth, B. R.

    1983-01-01

    A full factorial in simulator experiment of a single axis, multiloop, compensatory pitch tracking task is described. The experiment was conducted to provide data to validate extensions to an analytic, closed loop model of a real time digital simulation facility. The results of the experiment encompassing various simulation fidelity factors, such as visual delay, digital integration algorithms, computer iteration rates, control loading bandwidths and proprioceptive cues, and g-seat kinesthetic cues, are compared with predictions obtained from the analytic model incorporating an optimal control model of the human pilot. The in-simulator results demonstrate more sensitivity to the g-seat and to the control loader conditions than were predicted by the model. However, the model predictions are generally upheld, although the predicted magnitudes of the states and of the error terms are sometimes off considerably. Of particular concern is the large sensitivity difference for one control loader condition, as well as the model/in-simulator mismatch in the magnitude of the plant states when the other states match.

  8. Tutorial: Parallel Computing of Simulation Models for Risk Analysis.

    PubMed

    Reilly, Allison C; Staid, Andrea; Gao, Michael; Guikema, Seth D

    2016-10-01

    Simulation models are widely used in risk analysis to study the effects of uncertainties on outcomes of interest in complex problems. Often, these models are computationally complex and time consuming to run. This latter point may be at odds with time-sensitive evaluations or may limit the number of parameters that are considered. In this article, we give an introductory tutorial focused on parallelizing simulation code to better leverage modern computing hardware, enabling risk analysts to better utilize simulation-based methods for quantifying uncertainty in practice. This article is aimed primarily at risk analysts who use simulation methods but do not yet utilize parallelization to decrease the computational burden of these models. The discussion is focused on conceptual aspects of embarrassingly parallel computer code and software considerations. Two complementary examples are shown using the languages MATLAB and R. A brief discussion of hardware considerations is located in the Appendix.

  9. Propulsion simulation for magnetically suspended wind tunnel models

    NASA Technical Reports Server (NTRS)

    Joshi, Prakash B.; Beerman, Henry P.; Chen, James; Krech, Robert H.; Lintz, Andrew L.; Rosen, David I.

    1990-01-01

    The feasibility of simulating propulsion-induced aerodynamic effects on scaled aircraft models in wind tunnels employing Magnetic Suspension and Balance Systems. The investigation concerned itself with techniques of generating exhaust jets of appropriate characteristics. The objectives were to: (1) define thrust and mass flow requirements of jets; (2) evaluate techniques for generating propulsive gas within volume limitations imposed by magnetically-suspended models; (3) conduct simple diagnostic experiments for techniques involving new concepts; and (4) recommend experiments for demonstration of propulsion simulation techniques. Various techniques of generating exhaust jets of appropriate characteristics were evaluated on scaled aircraft models in wind tunnels with MSBS. Four concepts of remotely-operated propulsion simulators were examined. Three conceptual designs involving innovative adaptation of convenient technologies (compressed gas cylinders, liquid, and solid propellants) were developed. The fourth innovative concept, namely, the laser-assisted thruster, which can potentially simulate both inlet and exhaust flows, was found to require very high power levels for small thrust levels.

  10. Modeling and simulation of longwall scraper conveyor considering operational faults

    NASA Astrophysics Data System (ADS)

    Cenacewicz, Krzysztof; Katunin, Andrzej

    2016-06-01

    The paper provides a description of analytical model of a longwall scraper conveyor, including its electrical, mechanical, measurement and control actuating systems, as well as presentation of its implementation in the form of computer simulator in the Matlab®/Simulink® environment. Using this simulator eight scenarios typical of usual operational conditions of an underground scraper conveyor can be generated. Moreover, the simulator provides a possibility of modeling various operational faults and taking into consideration a measurement noise generated by transducers. The analysis of various combinations of scenarios of operation and faults with description is presented. The simulator developed may find potential application in benchmarking of diagnostic systems, testing of algorithms of operational control or can be used for supporting the modeling of real processes occurring in similar systems.

  11. Distributed collaborative environments for 21st century modeling and simulation

    NASA Astrophysics Data System (ADS)

    McQuay, William K.

    2001-09-01

    Distributed collaboration is an emerging technology that will significantly change how modeling and simulation is employed in 21st century organizations. Modeling and simulation (M&S) is already an integral part of how many organizations conduct business and, in the future, will continue to spread throughout government and industry enterprises and across many domains from research and development to logistics to training to operations. This paper reviews research that is focusing on the open standards agent-based framework, product and process modeling, structural architecture, and the integration technologies - the glue to integrate the software components. A distributed collaborative environment is the underlying infrastructure that makes communication between diverse simulations and other assets possible and manages the overall flow of a simulation based experiment. The AFRL Collaborative Environment concept will foster a major cultural change in how the acquisition, training, and operational communities employ M&S.

  12. Multibody model of the human upper extremity for fracture simulation

    PubMed Central

    Milanowicz, Marcin; Kędzior, Krzysztof

    2016-01-01

    About 3.8 million people are injured in accidents at work in Europe every year. The resulting high costs are incurred by the victims themselves, their families, employers and society. We have used a numerical simulation to reconstruct accidents at work for several years. To reconstruct these accidents MADYMO R7.5 with a numerical human model (pedestrian model) is used. However, this model is dedicated to the analysis of car-to-pedestrian accidents and thus cannot be fully used for reconstructing accidents at work. Therefore, we started working on the development of a numerical model of the human body for the purpose of simulating accidents at work. Developing a new numerical model which gives an opportunity to simulate fractures of the upper extremity bones is a stage of that work. PMID:26651896

  13. Analytic Model For Estimation Of Cold Bulk Metal Forming Simulations

    SciTech Connect

    Skunca, Marko; Keran, Zdenka; Math, Miljenko

    2007-05-17

    Numerical simulation of bulk metal forming plays an important role in predicting a key parameters in cold forging. Comparison of numerical and experimental data is of great importance, but there is always a need of more universal analytical tools. Therefore, many papers besides experiment and simulation of a particular bulk metal forming technology, include an analytic model. In this paper an analytical model for evaluation of commercially available simulation program packages is proposed. Based on elementary theory of plasticity, being only geometry dependent, model represents a good analytical reference to estimate given modeling preferences like; element types, solver, remeshing influence and many others. Obtained, geometry dependent, stress fields compared with numerical data give a clear picture of numerical possibilities and limitations of particular modeling program package.

  14. A Network Contention Model for the Extreme-scale Simulator

    SciTech Connect

    Engelmann, Christian; Naughton III, Thomas J

    2015-01-01

    The Extreme-scale Simulator (xSim) is a performance investigation toolkit for high-performance computing (HPC) hardware/software co-design. It permits running a HPC application with millions of concurrent execution threads, while observing its performance in a simulated extreme-scale system. This paper details a newly developed network modeling feature for xSim, eliminating the shortcomings of the existing network modeling capabilities. The approach takes a different path for implementing network contention and bandwidth capacity modeling using a less synchronous and accurate enough model design. With the new network modeling feature, xSim is able to simulate on-chip and on-node networks with reasonable accuracy and overheads.

  15. An improved human display model for occupant crash simulation programs

    NASA Technical Reports Server (NTRS)

    Willmert, K. D.; Potter, T. E.

    1975-01-01

    An improved three-dimensional display model of a human being which can be used to display the results of three-dimensional simulation programs that predict the positions of an occupant during impact of a vehicle was presented. The model allows the user to view the occupant from any orientation in any position during the crash. The display model assumes the usual break up of the body into rigid segments which is normal for occupant crash simulation programs, but the shape of the segments in the display model are not necessarily the same as those used in the crash simulation. The display model is proportioned so as to produce a realistic drawing of the human body in any position. Joints connecting the segments are also drawn to improve realism.

  16. Generation of linear dynamic models from a digital nonlinear simulation

    NASA Technical Reports Server (NTRS)

    Daniele, C. J.; Krosel, S. M.

    1979-01-01

    The results and methodology used to derive linear models from a nonlinear simulation are presented. It is shown that averaged positive and negative perturbations in the state variables can reduce numerical errors in finite difference, partial derivative approximations and, in the control inputs, can better approximate the system response in both directions about the operating point. Both explicit and implicit formulations are addressed. Linear models are derived for the F 100 engine, and comparisons of transients are made with the nonlinear simulation. The problem of startup transients in the nonlinear simulation in making these comparisons is addressed. Also, reduction of the linear models is investigated using the modal and normal techniques. Reduced-order models of the F 100 are derived and compared with the full-state models.

  17. Modeling and Simulation of Shuttle Launch and Range Operations

    NASA Technical Reports Server (NTRS)

    Bardina, Jorge; Thirumalainambi, Rajkumar

    2004-01-01

    The simulation and modeling test bed is based on a mockup of a space flight operations control suitable to experiment physical, procedural, software, hardware and psychological aspects of space flight operations. The test bed consists of a weather expert system to advise on the effect of weather to the launch operations. It also simulates toxic gas dispersion model, impact of human health risk, debris dispersion model in 3D visualization. Since all modeling and simulation is based on the internet, it could reduce the cost of operations of launch and range safety by conducting extensive research before a particular launch. Each model has an independent decision making module to derive the best decision for launch.

  18. Computer simulations for internal dosimetry using voxel models.

    PubMed

    Kinase, Sakae; Mohammadi, Akram; Takahashi, Masa; Saito, Kimiaki; Zankl, Maria; Kramer, Richard

    2011-07-01

    In the Japan Atomic Energy Agency, several studies have been conducted on the use of voxel models for internal dosimetry. Absorbed fractions (AFs) and S values have been evaluated for preclinical assessments of radiopharmaceuticals using human voxel models and a mouse voxel model. Computational calibration of in vivo measurement system has been also made using Japanese and Caucasian voxel models. In addition, for radiation protection of the environment, AFs have been evaluated using a frog voxel model. Each study was performed by using Monte Carlo simulations. Consequently, it was concluded that these data of Monte Carlo simulations and voxel models could adequately reproduce measurement results. Voxel models were found to be a significant tool for internal dosimetry since the models are anatomically realistic. This fact indicates that several studies on correction of the in vivo measurement efficiency for the variability of human subjects and interspecies scaling of organ doses will succeed.

  19. Generic Spacecraft Model for Real-Time Simulation

    NASA Technical Reports Server (NTRS)

    Kenney, Patrick S.; Ragsdale, William; Neuhaus, Jason R.

    2008-01-01

    Generic Spacecraft is the name of an evolving library of software that provides for simulation of a generic spacecraft that can orbit the Earth and land on the Moon (and, eventually, on Mars). This library is incorporated into the Langley Standard Realtime Simulation in C++ (LaSRS++) software framework. The generic-spacecraft simulation serves as a test bed for modeling spacecraft dynamics, propulsion, control systems, guidance, and displays. The Generic Spacecraft library supplements the LaSRS++ framework with an interface that facilitates the connection of new models into the LaSRS++ simulation by eliminating what would otherwise be the necessity of writing additional C++ classes to record data from the models and code to display values on graphical user interfaces (GUIs): The library includes routines for integrating new models into the LaSRS++ framework, identifying model inputs and outputs with full descriptions and units identified, recording data, and automatically generating graphical user interfaces (GUIs). The library is designed to be used in a manner similar to that of LaSRS++ software components for simulating vehicles other than the generic spacecraft. The user specifies (1) a spacecraft and individual models to be constructed and (2) connections between individual model inputs and outputs.

  20. Model for simulating rotational data for wind turbine applications

    SciTech Connect

    Powell, D.C.; Connell, J.R.

    1986-04-01

    This document describes a wind simulation model to be used in relation to wind turbine operations. The model is a computer code written in FORTRAN 77. The model simulates turbulence and mean wind effects as they are experienced at a rotating point on the blade of either a horizontal-axis wind turbine (HAWT) or a vertical-axis wind turbine (VAWT). The model is fast, requiring 15 to 120 seconds of VAX execution time to produce a simulation and related statistics. The model allows the user to set a number of wind parameters so that he may evaluate the uncertainty of model results as well as their typical values. When this capability is combined with short execution time, the user can quickly produce a number of simulations based on reasonable variation of input parameters and can use these simulations to obtain a range of wind turbine responses to the turbulence. This ability is important because some of the wind parameters that cannot be precisely evaluated should be prescribed over a range of values. This document is essentially a user's guide. Its features include theoretical derivations, samples of output, comparisons of measured and modeled results, a listing of the FORTRAN code, a glossary for the code, and the input and output of a sample run.

  1. Computer Model Simulates Air Pollution Over Roads

    ERIC Educational Resources Information Center

    Environmental Science and Technology, 1972

    1972-01-01

    A sophisticated modeling technique which predicts pollutant movement accurately and may aid in the design of new freeways is reported. EXPLOR (Examination of Pollution Levels of Roadways) was developed specifically to predict pollutant concentrations in a milewide corridor traversed by a roadway. (BL)

  2. Modeling and Simulation Terrain Database Management

    DTIC Science & Technology

    2005-07-01

    data for use in combat modeling. The SVDR is still under development by the Science Applications International Corporation (SAIC) in conjunction with...DOD organization for comunication between Unmanned Systems. But they have not worked on how to communicate terrain between systems. Hope this helps

  3. Collisional-Radiative Modeling In Flow Simulations

    DTIC Science & Technology

    2008-09-08

    based on Millikan -White’s formula including Park’s correction (52). For the vibrational-vibrational energy exchange, different formulations have been...modelling radiative transfer in atmospheric air mixture plasmas. Journal of Quantitative Spectroscopy and Radiative Transfer, 73:91–110. [59] Roberts , T. P

  4. Catalog of Wargaming and Military Simulation Models

    DTIC Science & Technology

    1989-09-01

    of the most widely used strategic force analysis models in the defense...and compares mobility capabilities of candidate ground vehicles for operation in selected areas of the world . It evaluates mobility capabilities in ...ellipt4cal distribution. The radial miss distance can be incremented. The program outpuf. in this mode can be used *to plot curves of single-shot

  5. Unit testing, model validation, and biological simulation

    PubMed Central

    Watts, Mark D.; Ghayoomie, S. Vahid; Larson, Stephen D.; Gerkin, Richard C.

    2016-01-01

    The growth of the software industry has gone hand in hand with the development of tools and cultural practices for ensuring the reliability of complex pieces of software. These tools and practices are now acknowledged to be essential to the management of modern software. As computational models and methods have become increasingly common in the biological sciences, it is important to examine how these practices can accelerate biological software development and improve research quality. In this article, we give a focused case study of our experience with the practices of unit testing and test-driven development in OpenWorm, an open-science project aimed at modeling Caenorhabditis elegans. We identify and discuss the challenges of incorporating test-driven development into a heterogeneous, data-driven project, as well as the role of model validation tests, a category of tests unique to software which expresses scientific models. PMID:27635225

  6. Comparison of climate model simulated and observed borehole temperature profiles

    NASA Astrophysics Data System (ADS)

    Gonzalez-Rouco, J. F.; Stevens, M. B.; Beltrami, H.; Goosse, H.; Rath, V.; Zorita, E.; Smerdon, J.

    2009-04-01

    Advances in understanding climate variability through the last millennium lean on simulation and reconstruction efforts. Progress in the integration of both approaches can potentially provide new means of assessing confidence on model projections of future climate change, of constraining the range of climate sensitivity and/or attributing past changes found in proxy evidence to external forcing. This work addresses specifically possible strategies for comparison of paleoclimate model simulations and the information recorded in borehole temperature profiles (BTPs). First efforts have allowed to design means of comparison of model simulated and observed BTPs in the context of the climate of the last millennium. This can be done by diffusing the simulated temperatures into the ground in order to produce synthetic BTPs that can be in turn assigned to collocated, real BTPs. Results suggest that there is sensitivity of borehole temperatures at large and regional scales to changes in external forcing over the last centuries. The comparison between borehole climate reconstructions and model simulations may also be subjected to non negligible uncertainties produced by the influence of past glacial and Holocene changes. While the thermal climate influence of the last deglaciation can be found well below 1000 m depth, such type of changes can potentially exert an influence on our understanding of subsurface climate in the top ca. 500 m. This issue is illustrated in control and externally forced climate simulations of the last millennium with the ECHO-G and LOVECLIM models, respectively.

  7. A Multiagent Modeling Environment for Simulating Work Practice in Organizations

    NASA Technical Reports Server (NTRS)

    Sierhuis, Maarten; Clancey, William J.; vanHoof, Ron

    2004-01-01

    In this paper we position Brahms as a tool for simulating organizational processes. Brahms is a modeling and simulation environment for analyzing human work practice, and for using such models to develop intelligent software agents to support the work practice in organizations. Brahms is the result of more than ten years of research at the Institute for Research on Learning (IRL), NYNEX Science & Technology (the former R&D institute of the Baby Bell telephone company in New York, now Verizon), and for the last six years at NASA Ames Research Center, in the Work Systems Design and Evaluation group, part of the Computational Sciences Division (Code IC). Brahms has been used on more than ten modeling and simulation research projects, and recently has been used as a distributed multiagent development environment for developing work practice support tools for human in-situ science exploration on planetary surfaces, in particular a human mission to Mars. Brahms was originally conceived of as a business process modeling and simulation tool that incorporates the social systems of work, by illuminating how formal process flow descriptions relate to people s actual located activities in the workplace. Our research started in the early nineties as a reaction to experiences with work process modeling and simulation . Although an effective tool for convincing management of the potential cost-savings of the newly designed work processes, the modeling and simulation environment was only able to describe work as a normative workflow. However, the social systems, uncovered in work practices studied by the design team played a significant role in how work actually got done-actual lived work. Multi- tasking, informal assistance and circumstantial work interactions could not easily be represented in a tool with a strict workflow modeling paradigm. In response, we began to develop a tool that would have the benefits of work process modeling and simulation, but be distinctively able to

  8. Rasterizing geological models for parallel finite difference simulation using seismic simulation as an example

    NASA Astrophysics Data System (ADS)

    Zehner, Björn; Hellwig, Olaf; Linke, Maik; Görz, Ines; Buske, Stefan

    2016-01-01

    3D geological underground models are often presented by vector data, such as triangulated networks representing boundaries of geological bodies and geological structures. Since models are to be used for numerical simulations based on the finite difference method, they have to be converted into a representation discretizing the full volume of the model into hexahedral cells. Often the simulations require a high grid resolution and are done using parallel computing. The storage of such a high-resolution raster model would require a large amount of storage space and it is difficult to create such a model using the standard geomodelling packages. Since the raster representation is only required for the calculation, but not for the geometry description, we present an algorithm and concept for rasterizing geological models on the fly for the use in finite difference codes that are parallelized by domain decomposition. As a proof of concept we implemented a rasterizer library and integrated it into seismic simulation software that is run as parallel code on a UNIX cluster using the Message Passing Interface. We can thus run the simulation with realistic and complicated surface-based geological models that are created using 3D geomodelling software, instead of using a simplified representation of the geological subsurface using mathematical functions or geometric primitives. We tested this set-up using an example model that we provide along with the implemented library.

  9. Potts-model grain growth simulations: Parallel algorithms and applications

    SciTech Connect

    Wright, S.A.; Plimpton, S.J.; Swiler, T.P.

    1997-08-01

    Microstructural morphology and grain boundary properties often control the service properties of engineered materials. This report uses the Potts-model to simulate the development of microstructures in realistic materials. Three areas of microstructural morphology simulations were studied. They include the development of massively parallel algorithms for Potts-model grain grow simulations, modeling of mass transport via diffusion in these simulated microstructures, and the development of a gradient-dependent Hamiltonian to simulate columnar grain growth. Potts grain growth models for massively parallel supercomputers were developed for the conventional Potts-model in both two and three dimensions. Simulations using these parallel codes showed self similar grain growth and no finite size effects for previously unapproachable large scale problems. In addition, new enhancements to the conventional Metropolis algorithm used in the Potts-model were developed to accelerate the calculations. These techniques enable both the sequential and parallel algorithms to run faster and use essentially an infinite number of grain orientation values to avoid non-physical grain coalescence events. Mass transport phenomena in polycrystalline materials were studied in two dimensions using numerical diffusion techniques on microstructures generated using the Potts-model. The results of the mass transport modeling showed excellent quantitative agreement with one dimensional diffusion problems, however the results also suggest that transient multi-dimension diffusion effects cannot be parameterized as the product of the grain boundary diffusion coefficient and the grain boundary width. Instead, both properties are required. Gradient-dependent grain growth mechanisms were included in the Potts-model by adding an extra term to the Hamiltonian. Under normal grain growth, the primary driving term is the curvature of the grain boundary, which is included in the standard Potts-model Hamiltonian.

  10. Modeling of an industrial alcohol fermentation and simulation of the plant by a process simulator

    SciTech Connect

    Pascal, F.; Corriou, J.P.; Pons, M.N.; Dagot, C.; Engasser, J.M.; Pingaud, H.

    1995-05-05

    The aim of the present study was the development of a general simulation module for fermentation within the framework of existing chemical process simulators. This module has been applied to an industrial plant which produces ethanol from beet molasses and fresh beet juice by Saccharomyces cerevisiae. An unstructured mechanistic model has been developed with kinetic laws that are based on a chemically defined reaction scheme which satisfies stoichiometric constraints. This model can be applied to different culture conditions and takes into account secondary byproducts such as higher alcohols. These byproducts are of prime importance and need to be correctly estimated because a sequence of distillation columns follow the fermentor in the plant. Important measurement campaigns have been performed on the plant to validate the model. Plant operation has been successfully simulated using the same kinetic model for both continuous and fed-batch modes of production.

  11. Winter and summer simulations with the GLAS climate model

    NASA Technical Reports Server (NTRS)

    Shukla, J.; Straus, D.; Randall, D.; Sud, Y.; Marx, L.

    1981-01-01

    The GLAS climate model is a general circulation model based on the primitive equations in sigma coordinates on a global domain in the presence of orography. The model incorporates parameterizations of the effects of radiation, convection, large scale latent heat release, turbulent and boundary layer fluxes, and ground hydrology. Winter and summer simulations were carried out with this model, and the resulting data are compared to observations.

  12. URC Fuzzy Modeling and Simulation of Gene Regulation

    DTIC Science & Technology

    2007-11-02

    URC FUZZY MODELING AND SIMULATION OF GENE REGULATION B. A. Sokhansanj1,2 and J. P. Fitch1 1Biology and Biotechnology Research Program, Lawrence...engineering, pharmaceuticals , gene therapy). Diverse modeling approaches have been proposed, in two general categories: modeling a biological pathway as (a) a...systems, we propose that fuzzy logic is a natural language for modeling biology. The Union Rule Configuration (URC) avoids combinatorial explosion in the

  13. HYBRIST Mobility Model - A Novel Hybrid Mobility Model for VANET Simulations

    NASA Astrophysics Data System (ADS)

    ManfeDanquah, Wiseborn; Turgay Altilar, D.

    2014-01-01

    Simulations play a vital role in implementing, testing and validating proposed algorithms and protocols in VANET. Mobility model, defined as the movement pattern of vehicles, is one of the main factors that contribute towards the efficient implementation of VANET algorithms and protocols. Using near reality mobility models ensure that accurate results are obtained from simulations. Mobility models that have been proposed and used to implement and test VANET protocols and algorithms are either the urban mobility model or highway mobility model. Algorithms and protocols implemented using urban or highway mobility models may not produce accurate results in hybrid mobility models without enhancement due to the vast differences in mobility patterns. It is on this score the Hybrist, a novel hybrid mobility model is proposed. The realistic mobility pattern trace file of the proposed Hybrist hybrid mobility model can be imported to VANET simulators such as Veins and network simulators such as ns2 and Qualnet to simulate VANET algorithms and protocols.

  14. Characterization of fluvial sedimentology for reservoir simulation modeling

    SciTech Connect

    Henriquez, A.; Tyler, K.J.; Hurst, A. )

    1990-09-01

    This paper presents a critical study of 3D stochastic simulation of a fluvial reservoir and of the transfer of the geological model to a reservoir simulation grid. The stochastic model is conditioned by sand-body thickness and position in wellbores. Geological input parameters-sand-body orientation and width/thickness ratios-are often difficult to determine, and are invariably subject to interpretation. Net/gross ratio (NGR) and sand-body thickness are more easily estimated. Sand-body connectedness varies, depending on the modeling procedure; however, a sedimentary process-related model gives intermediate values for connectedness between the values for a regular packing model and the stochastic model. The geological model is transferred to a reservoir simulation grid by use of transmissibility multipliers and an NGR value for each block. The transfer of data smooths out much of the detailed geological information, and the calculated recovery factors are insensitive to the continuity measured in the geological model. Hence, the authors propose improvements to the interface between geological and reservoir simulation models.

  15. Developing Soil Models for Dynamic Impact Simulations

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin L.; Lyle, Karen H.; Jackson, Karen E.

    2009-01-01

    This paper describes fundamental soils characterization work performed at NASA Langley Research Center in support of the Subsonic Rotary Wing (SRW) Aeronautics Program and the Orion Landing System (LS) Advanced Development Program (ADP). LS-DYNA(Registered TradeMark)1 soil impact model development and test-analysis correlation results are presented for: (1) a 38-ft/s vertical drop test of a composite fuselage section, outfitted with four blocks of deployable energy absorbers (DEA), onto sand, and (2) a series of impact tests of a 1/2-scale geometric boilerplate Orion capsule onto soil. In addition, the paper will discuss LS-DYNA contact analysis at the soil/structure interface, methods used to estimate frictional forces, and the sensitivity of the model to density, moisture, and compaction.

  16. Ocean Simulation Model for Internal Waves

    DTIC Science & Technology

    1990-08-01

    MODEL1.DAT U D 4°NZ Real U,V,W, (U(i),V(i),W(i), Z Z(i), i= 1 ,NZ) MODEL1.AUX U S 3°NZ Real NT,NX,NZ,DT, NTNX,NZDT, DXDZ,T0, LAT , DX,DZ,T0, LAT , LON,AZ LON...Oceanographic and Atmospheric Research Laboratory, Stennis Space Center, Mississippi 39529-5004. 9 1 .... .... . .. ...8 I I I II I I Foreword The effects of the...I A. Background 1 B. Project Objectives 1 C. Purpose of This Manual 1 II. Background and Derivation of Algorithms 2 A. Stochastic Representation of

  17. Lattice Boltzmann model for simulation of magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Chen, Shiyi; Chen, Hudong; Martinez, Daniel; Matthaeus, William

    1991-01-01

    A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.

  18. Geometry and Grid Modeling for Numerical Simulation

    DTIC Science & Technology

    2005-06-01

    three dimensional spatial region (a mesh) is a prerequisite of most computer aided engineering ( CAE ) software, including computational structural...Parasolid Parasolid [13] is a commercial solid-modeling kernel. It serves as the basis for Unigraphics and several other CAD/CAM/ CAE packages. It is...As mentioned earlier, 1D and 2D arrays of standard data types are the most complex data type permitted. This method has the advantage of

  19. Simulation of large-scale rule-based models

    SciTech Connect

    Hlavacek, William S; Monnie, Michael I; Colvin, Joshua; Faseder, James

    2008-01-01

    Interactions of molecules, such as signaling proteins, with multiple binding sites and/or multiple sites of post-translational covalent modification can be modeled using reaction rules. Rules comprehensively, but implicitly, define the individual chemical species and reactions that molecular interactions can potentially generate. Although rules can be automatically processed to define a biochemical reaction network, the network implied by a set of rules is often too large to generate completely or to simulate using conventional procedures. To address this problem, we present DYNSTOC, a general-purpose tool for simulating rule-based models. DYNSTOC implements a null-event algorithm for simulating chemical reactions in a homogenous reaction compartment. The simulation method does not require that a reaction network be specified explicitly in advance, but rather takes advantage of the availability of the reaction rules in a rule-based specification of a network to determine if a randomly selected set of molecular components participates in a reaction during a time step. DYNSTOC reads reaction rules written in the BioNetGen language which is useful for modeling protein-protein interactions involved in signal transduction. The method of DYNSTOC is closely related to that of STOCHSIM. DYNSTOC differs from STOCHSIM by allowing for model specification in terms of BNGL, which extends the range of protein complexes that can be considered in a model. DYNSTOC enables the simulation of rule-based models that cannot be simulated by conventional methods. We demonstrate the ability of DYNSTOC to simulate models accounting for multisite phosphorylation and multivalent binding processes that are characterized by large numbers of reactions. DYNSTOC is free for non-commercial use. The C source code, supporting documentation and example input files are available at .

  20. Integrated Turbine-Based Combined Cycle Dynamic Simulation Model

    NASA Technical Reports Server (NTRS)

    Haid, Daniel A.; Gamble, Eric J.

    2011-01-01

    A Turbine-Based Combined Cycle (TBCC) dynamic simulation model has been developed to demonstrate all modes of operation, including mode transition, for a turbine-based combined cycle propulsion system. The High Mach Transient Engine Cycle Code (HiTECC) is a highly integrated tool comprised of modules for modeling each of the TBCC systems whose interactions and controllability affect the TBCC propulsion system thrust and operability during its modes of operation. By structuring the simulation modeling tools around the major TBCC functional modes of operation (Dry Turbojet, Afterburning Turbojet, Transition, and Dual Mode Scramjet) the TBCC mode transition and all necessary intermediate events over its entire mission may be developed, modeled, and validated. The reported work details the use of the completed model to simulate a TBCC propulsion system as it accelerates from Mach 2.5, through mode transition, to Mach 7. The completion of this model and its subsequent use to simulate TBCC mode transition significantly extends the state-of-the-art for all TBCC modes of operation by providing a numerical simulation of the systems, interactions, and transient responses affecting the ability of the propulsion system to transition from turbine-based to ramjet/scramjet-based propulsion while maintaining constant thrust.

  1. Blood vessel modeling for interactive simulation of interventional neuroradiology procedures.

    PubMed

    Kerrien, E; Yureidini, A; Dequidt, J; Duriez, C; Anxionnat, R; Cotin, S

    2017-01-01

    Endovascular interventions can benefit from interactive simulation in their training phase but also during pre-operative and intra-operative phases if simulation scenarios are based on patient data. A key feature in this context is the ability to extract, from patient images, models of blood vessels that impede neither the realism nor the performance of simulation. This paper addresses both the segmentation and reconstruction of the vasculature from 3D Rotational Angiography data, and adapted to simulation: An original tracking algorithm is proposed to segment the vessel tree while filtering points extracted at the vessel surface in the vicinity of each point on the centerline; then an automatic procedure is described to reconstruct each local unstructured point set as a skeleton-based implicit surface (blobby model). The output of successively applying both algorithms is a new model of vasculature as a tree of local implicit models. The segmentation algorithm is compared with Multiple Hypothesis Testing (MHT) algorithm (Friman et al., 2010) on patient data, showing its greater ability to track blood vessels. The reconstruction algorithm is evaluated on both synthetic and patient data and demonstrate its ability to fit points with a subvoxel precision. Various tests are also reported where our model is used to simulate catheter navigation in interventional neuroradiology. An excellent realism, and much lower computational costs are reported when compared to triangular mesh surface models.

  2. Simulation model of a twin-tail, high performance airplane

    NASA Technical Reports Server (NTRS)

    Buttrill, Carey S.; Arbuckle, P. Douglas; Hoffler, Keith D.

    1992-01-01

    The mathematical model and associated computer program to simulate a twin-tailed high performance fighter airplane (McDonnell Douglas F/A-18) are described. The simulation program is written in the Advanced Continuous Simulation Language. The simulation math model includes the nonlinear six degree-of-freedom rigid-body equations, an engine model, sensors, and first order actuators with rate and position limiting. A simplified form of the F/A-18 digital control laws (version 8.3.3) are implemented. The simulated control law includes only inner loop augmentation in the up and away flight mode. The aerodynamic forces and moments are calculated from a wind-tunnel-derived database using table look-ups with linear interpolation. The aerodynamic database has an angle-of-attack range of -10 to +90 and a sideslip range of -20 to +20 degrees. The effects of elastic deformation are incorporated in a quasi-static-elastic manner. Elastic degrees of freedom are not actively simulated. In the engine model, the throttle-commanded steady-state thrust level and the dynamic response characteristics of the engine are based on airflow rate as determined from a table look-up. Afterburner dynamics are switched in at a threshold based on the engine airflow and commanded thrust.

  3. Advanced Chemical Modeling for Turbulent Combustion Simulations

    DTIC Science & Technology

    2012-05-03

    combustor conditions. The resolved DNS dissipation rate is reasonably well described by the resolved component of the LES model (black solid line...our computed results with the non-linearly extrapolated burning velocities for m-xylene. 66 0 100 200 300 400 0 30 60 90 120 M ol e fr ac ...tio n [p pm ] t [ms] A1(CH3)2 x0.2 A1CH3 (a) 0 2 4 6 8 0 30 60 90 120 M ol e fr ac tio n [p pm ] t [ms] A1C2H5 (b) 0 20 40 60 80 100

  4. Models Robustness for Simulating Drainage and NO3-N Fluxes

    NASA Astrophysics Data System (ADS)

    Jabro, Jay; Jabro, Ann

    2013-04-01

    Computer models simulate and forecast appropriate agricultural practices to reduce environmental impact. The objectives of this study were to assess and compare robustness and performance of three models -- LEACHM, NCSWAP, and SOIL-SOILN--for simulating drainage and NO3-N leaching fluxes in an intense pasture system without recalibration. A 3-yr study was conducted on a Hagerstown silt loam to measure drainage and NO3-N fluxes below 1 m depth from N-fertilized orchardgrass using intact core lysimeters. Five N-fertilizer treatments were replicated five times in a randomized complete block experimental design. The models were validated under orchardgrass using soil, water and N transformation rate parameters and C pools fractionation derived from a previous study conducted on similar soils under corn. The model efficiency (MEF) of drainage and NO3-N fluxes were 0.53, 0.69 for LEACHM; 0.75, 0.39 for NCSWAP; and 0.94, 0.91for SOIL-SOILN. The models failed to produce reasonable simulations of drainage and NO3-N fluxes in January, February and March due to limited water movement associated with frozen soil and snow accumulation and melt. The differences between simulated and measured NO3-N leaching and among models' performances may also be related to soil N and C transformation processes embedded in the models These results are a monumental progression in the validation of computer models which will lead to continued diffusion across diverse stakeholders.

  5. An Urban Diffusion Simulation Model for Carbon Monoxide

    ERIC Educational Resources Information Center

    Johnson, W. B.; And Others

    1973-01-01

    A relatively simple Gaussian-type diffusion simulation model for calculating urban carbon (CO) concentrations as a function of local meteorology and the distribution of traffic is described. The model can be used in two ways: in the synoptic mode and in the climatological mode. (Author/BL)

  6. Realization of State-Space Models for Wave Propagation Simulations

    DTIC Science & Technology

    2012-01-01

    turquoise ). 13 Verification and Performance of Superstable Model The second FDTD analysis was to verify that a simulation using the...another, so that the turquoise and red lines are all that are visible). The implication is that model-order reduction can serve a useful purpose when

  7. Physically-based Modeling and Simulation of Extraocular Muscles

    PubMed Central

    Wei, Qi; Sueda, Shinjiro; Pai, Dinesh K.

    2010-01-01

    Dynamic simulation of human eye movements, with realistic physical models of extraocular muscles (EOMs), may greatly advance our understanding of the complexities of the oculomotor system and aid in treatment of visuomotor disorders. In this paper we describe the first three dimensional (3D) biomechanical model which can simulate the dynamics of ocular motility at interactive rates. We represent EOMs using “strands”, which are physical primitives that can model an EOM's complex nonlinear anatomical and physiological properties. Contact between the EOMs, the globe, and orbital structures can be explicitly modeled. Several studies were performed to assess the validity and utility of the model. EOM deformation during smooth pursuit was simulated and compared with published experimental data; the model reproduces qualitative features of the observed non-uniformity. The model is able to reproduce realistic saccadic trajectories when the lateral rectus muscle was driven by published measurements of abducens neuron discharge. Finally, acute superior oblique palsy, a pathological condition, was simulated to further evaluate the system behavior; the predicted deviation patterns agree qualitatively with experimental observations. This example also demonstrates potential clinical applications of such a model. PMID:20868704

  8. Computer Simulation of Small Group Decisions: Model Three.

    ERIC Educational Resources Information Center

    Hare, A.P.; Scheiblechner, Hartmann

    In a test of three computer models to simulate group decisions, data were used from 31 American and Austrian groups on a total of 307 trials. The task for each group was to predict a series of answers of an unknown subject on a value-orientation questionnaire, after being given a sample of his typical responses. The first model, used the mean of…

  9. ARTEMIS: Ares Real Time Environments for Modeling, Integration, and Simulation

    NASA Technical Reports Server (NTRS)

    Hughes, Ryan; Walker, David

    2009-01-01

    This slide presentation reviews the use of ARTEMIS in the development and testing of the ARES launch vehicles. Ares Real Time Environment for Modeling, Simulation and Integration (ARTEMIS) is the real time simulation supporting Ares I hardware-in-the-loop (HWIL) testing. ARTEMIS accurately models all Ares/Orion/Ground subsystems which interact with Ares avionics components from pre-launch through orbit insertion The ARTEMIS System integration Lab, and the STIF architecture is reviewed. The functional components of ARTEMIS are outlined. An overview of the models and a block diagram is presented.

  10. Rheological Models of Blood: Sensitivity Analysis and Benchmark Simulations

    NASA Astrophysics Data System (ADS)

    Szeliga, Danuta; Macioł, Piotr; Banas, Krzysztof; Kopernik, Magdalena; Pietrzyk, Maciej

    2010-06-01

    Modeling of blood flow with respect to rheological parameters of the blood is the objective of this paper. Casson type equation was selected as a blood model and the blood flow was analyzed based on Backward Facing Step benchmark. The simulations were performed using ADINA-CFD finite element code. Three output parameters were selected, which characterize the accuracy of flow simulation. Sensitivity analysis of the results with Morris Design method was performed to identify rheological parameters and the model output, which control the blood flow to significant extent. The paper is the part of the work on identification of parameters controlling process of clotting.

  11. NTP system simulation and detailed nuclear engine modeling

    NASA Technical Reports Server (NTRS)

    Anghaie, Samim

    1993-01-01

    The topics are presented in viewgraph form and include the following: nuclear thermal propulsion (NTP) & detailed nuclear engine modeling; modeling and engineering simulation of nuclear thermal rocket systems; nuclear thermal rocket simulation system; INSPI-NTVR core axial flow profiles; INSPI-NTRV core axial flow profiles; specific impulse vs. chamber pressure; turbine pressure ratio vs. chamber pressure; NERVA core axial flow profiles; P&W XNR2000 core axial flow profiles; pump pressure rise vs. chamber pressure; streamline of jet-induced flow in cylindrical chamber; flow pattern of a jet-induced flow in a chamber; and radiative heat transfer models.

  12. Description of a tilt wing mathematical model for piloted simulation

    NASA Technical Reports Server (NTRS)

    Totah, Joseph J.

    1991-01-01

    A tilt-wing mathematical model that was used in a piloted six-deg-of-freedom flight simulation application is presented. Two types of control systems developed for the model - a conventional programmed-flap wing-tilt control system and a geared-flap wing-tilt control system - are discussed. The objective of this effort was to develop the capability to study tilt-wing aircraft. Experienced tilt-wing pilots subjectively evaluated the model using programmed-flap control to assess the quality of the simulation. The objective was met and the model was then applied to study geared-flap control to investigate the possibility of eliminating the need for auxiliary pitch control devices. This was performed in the moving-base simulation environment, and the vehicle responses with programmed-flap and geared-flap control were compared.

  13. Software Platform Evaluation - Verifiable Fuel Cycle Simulation (VISION) Model

    SciTech Connect

    J. J. Jacobson; D. E. Shropshire; W. B. West

    2005-11-01

    The purpose of this Software Platform Evaluation (SPE) is to document the top-level evaluation of potential software platforms on which to construct a simulation model that satisfies the requirements for a Verifiable Fuel Cycle Simulation Model (VISION) of the Advanced Fuel Cycle (AFC). See the Software Requirements Specification for Verifiable Fuel Cycle Simulation (VISION) Model (INEEL/EXT-05-02643, Rev. 0) for a discussion of the objective and scope of the VISION model. VISION is intended to serve as a broad systems analysis and study tool applicable to work conducted as part of the AFCI (including costs estimates) and Generation IV reactor development studies. This document will serve as a guide for selecting the most appropriate software platform for VISION. This is a “living document” that will be modified over the course of the execution of this work.

  14. RAM simulation model for SPH/RSV systems

    SciTech Connect

    Schryver, J.C.; Primm, A.H.; Nelson, S.C.

    1995-12-31

    The US Army`s Project Manager, Crusader is sponsoring the development of technologies that apply to the Self-Propelled Howitzer (SPH), formerly the Advanced Field Artillery System (AFAS), and Resupply Vehicle (RSV), formerly the Future Armored Resupply Vehicle (FARV), weapon system. Oak Ridge National Laboratory (ORNL) is currently performing developmental work in support of the SPH/PSV Crusader system. Supportive analyses of reliability, availability, and maintainability (RAM) aspects were also performed for the SPH/RSV effort. During FY 1994 and FY 1995 OPNL conducted a feasibility study to demonstrate the application of simulation modeling for RAM analysis of the Crusader system. Following completion of the feasibility study, a full-scale RAM simulation model of the Crusader system was developed for both the SPH and PSV. This report provides documentation for the simulation model as well as instructions in the proper execution and utilization of the model for the conduct of RAM analyses.

  15. Thermohaline circulation and its box models simulation

    NASA Astrophysics Data System (ADS)

    Bazyura, Kateryna; Polonsky, Alexander; Sannikov, Viktor

    2014-05-01

    Ocean Thermochaline circulation (THC) is the part of large-scale World Ocean circulation and one of the main climate system components. It is generated by global meridional density gradients, which are controlled by surface heat and freshwater fluxes. THC regulates climate variability on different timescales (from decades to thousands years) [Stocker (2000), Clark (2002)]. Study of paleoclimatic evidences of abrupt and dramatic changes in ocean-atmosphere system in the past (such as, Dansgaard-Oeschger and Heinrich events or Younger Dryas, see e.g., [Rahmstorf (2002), Alley & Clark(1999)]) shows that these events are connected with THC regimes. At different times during last 120,000 years, three THC modes have prevailed in the Atlantic. They can be labeled as stadial, interstadial and Heinrich modes or as cold, warm and off mode. THC collapse (or thermohaline catastrophe) can be one of the consequences of global warming (including modern anthropogenic climate changes occurring at the moment). The ideas underlying different box-model studies, possibility of thermochaline catastrophe in present and past are discussed in this presentation. Response of generalized four box model of North Atlantic thermohaline circulation [developing the model of Griffies & Tzippermann (1995)] on periodic, stochastic and linear forcing is studied in details. To estimate climatic parameters of the box model we used monthly salinity and temperature data of ECMWF operational Ocean Reanalysis System 3 (ORA-S3) and data from atmospheric NCEP/NCAR reanalysis on precipitation, and heat fluxes for 1959-2011. Mean values, amplitude of seasonal cycle, amplitudes and periods of typical interdecadal oscillations, white noise level, linear trend coefficients and their significance level were estimated for every hydrophysical parameter. In response to intense freshwater or heat forcing, THC regime can change resulting in thermohaline catastrophe. We analyze relevant thresholds of external forcing in

  16. Modeling High Resolution Flare Spectra Using Hydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Warren, Harry; Doschek, G.

    2006-06-01

    Understanding the hydrodynamic response of the solar atmosphere to the release of energy during a flare has been a long standing problem in solar physics. Early time-dependent hydrodynamic simulations were able to reproduce the high temperatures and densities observed in solar flares, but were not able to model the observations in any detail. For example, these simulations could not account for the relatively slow decay of the observed emission or the absence of blueshifts in high spectral resolution line profiles at flare onset. We have found that by representing the flare as a succession of independently heated filaments it is possible to reproduce both the evolution of line intensity and the shape of the line profile using hydrodynamic simulations. Here we present detailed comparisons between our simulation results and several flares observed with the Yohkoh Bragg Crystal Spectrometer (BCS). Comparisons with 3D MHD simulations will also be discussed.

  17. Upper Rio Grande Simulation Model (URGSIM)

    SciTech Connect

    Roach, Jesse; & Tidwell, Vincent

    2010-08-05

    URGSIM estimates the location of surface water and groundwater resources in the upper Rio Grande Basin between the Colorado-New Mexico state line, and Caballo Reservoir from 1975 - 2045. It is a mass balance hydrology model of the Upper Rio Grande surface water, groundwater, and water demand systems which runs at a monthly timestep from 1975-1999 in calibration mode, 2000 – 2004 in validation mode, and 2005 – 2045 in scenario analysis mode.

  18. Modeling and Simulation of Semiconductor Quantum Well Structures and Lasers

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Saini, Subbash (Technical Monitor)

    1998-01-01

    In this talk I will cover two aspects of modeling and simulation efforts at NASA Ames Research Center. In the quantum well structure simulation, we typically start from the quantum mechanical calculation of the quantum well structures for the confined/and unconfined eigen states and functions. A bandstructure calculation of the k*p type is then performed for the confined valence states. This information is then used to computer the optical gain and refractive index of the quantum well structures by solving the linearized multiband semiconductor Bloch equations with the many-body interactions included. In our laser simulation, we typically solve the envelope equations for the laser field in space-time domain, coupled with a reduced set of material equations using the microscopic calculation of the first step. Finally I will show some examples of both aspects of simulation and modeling.

  19. Simulations of Keratoconus Patient Vision with Optical Eye Modeling

    NASA Astrophysics Data System (ADS)

    Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Shi, Lei; Wang, Ming

    2007-11-01

    Keratoconus (KC) is an eye condition that involves progressive corneal thinning. Pushed by the intraocular pressure, the weakened cornea bulges outward and creates an irregular surface shape. The result is degraded vision that is difficult to correct with regular eye glasses or contact lens. In this study we use the optical lens design software, ZeMax, and patient data including cornea topography and refraction prescription to construct KC eye models. The variation of KC ``cone height'' on the cornea is used to simulate KC progression. The consequent patients' night vision and Snellen letter chart vision at 20 feet are simulated using these anatomically accurate 3-dimensional models. 100 million rays are traced for each image simulation. Animated results illustrate the change of KC visual acuity with the progression of disease. This simulation technique provides a comprehensive tool for medical training and patient consultation/education.

  20. Modeling, Simulation and Analysis of Public Key Infrastructure

    NASA Technical Reports Server (NTRS)

    Liu, Yuan-Kwei; Tuey, Richard; Ma, Paul (Technical Monitor)

    1998-01-01

    Security is an essential part of network communication. The advances in cryptography have provided solutions to many of the network security requirements. Public Key Infrastructure (PKI) is the foundation of the cryptography applications. The main objective of this research is to design a model to simulate a reliable, scalable, manageable, and high-performance public key infrastructure. We build a model to simulate the NASA public key infrastructure by using SimProcess and MatLab Software. The simulation is from top level all the way down to the computation needed for encryption, decryption, digital signature, and secure web server. The application of secure web server could be utilized in wireless communications. The results of the simulation are analyzed and confirmed by using queueing theory.

  1. Modeling and simulation of dust behaviors behind a moving vehicle

    NASA Astrophysics Data System (ADS)

    Wang, Jingfang

    Simulation of physically realistic complex dust behaviors is a difficult and attractive problem in computer graphics. A fast, interactive and visually convincing model of dust behaviors behind moving vehicles is very useful in computer simulation, training, education, art, advertising, and entertainment. In my dissertation, an experimental interactive system has been implemented for the simulation of dust behaviors behind moving vehicles. The system includes physically-based models, particle systems, rendering engines and graphical user interface (GUI). I have employed several vehicle models including tanks, cars, and jeeps to test and simulate in different scenarios and conditions. Calm weather, winding condition, vehicle turning left or right, and vehicle simulation controlled by users from the GUI are all included. I have also tested the factors which play against the physical behaviors and graphics appearances of the dust particles through GUI or off-line scripts. The simulations are done on a Silicon Graphics Octane station. The animation of dust behaviors is achieved by physically-based modeling and simulation. The flow around a moving vehicle is modeled using computational fluid dynamics (CFD) techniques. I implement a primitive variable and pressure-correction approach to solve the three dimensional incompressible Navier Stokes equations in a volume covering the moving vehicle. An alternating- direction implicit (ADI) method is used for the solution of the momentum equations, with a successive-over- relaxation (SOR) method for the solution of the Poisson pressure equation. Boundary conditions are defined and simplified according to their dynamic properties. The dust particle dynamics is modeled using particle systems, statistics, and procedure modeling techniques. Graphics and real-time simulation techniques, such as dynamics synchronization, motion blur, blending, and clipping have been employed in the rendering to achieve realistic appearing dust

  2. Rejection-free stochastic simulation of BNGL-encoded models

    SciTech Connect

    Hlavacek, William S; Monine, Michael I; Colvin, Joshua; Posner, Richard G; Von Hoff, Daniel D

    2009-01-01

    Formal rules encoded using the BioNetGen language (BNGL) can be used to represent the system-level dynamics of molecular interactions. Rules allow one to compactly and implicitly specify the reaction network implied by a set of molecules and their interactions. Typically, the reaction network implied by a set of rules is large, which makes generation of the underlying rule-defined network expensive. Moreover, the cost of conventional simulation methods typically depends on network size. Together these factors have limited application of the rule-based modeling approach. To overcome this limitation, several methods have recently been developed for determining the reaction dynamics implied by rules while avoiding the expensive step of network generation. The cost of these 'network-free' simulation methods is independent of the number of reactions implied by rules. Software implementing such methods is needed for the analysis of rule-based models of biochemical systems. Here, we present a software tool called RuleMonkey that implements a network-free stochastic simulation method for rule-based models. The method is rejection free, unlike other network-free methods that introduce null events (i.e., steps in the simulation procedure that do not change the state of the reaction system being simulated), and the software is capable of simulating models encoded in BNGL, a general-purpose model-specification language. We verify that RuleMonkey produces correct simulation results, and we compare its performance against DYNSTOC, another BNGL-compliant general-purpose simulator for rule-based models, as well as various problem-specific codes that implement network-free simulation methods. RuleMonkey enables the simulation of models defined by rule sets that imply large-scale reaction networks. It is faster than DYNSTOC for stiff problems, although it requires the use of more computer memory. RuleMonkey is freely available for non-commercial use as a stand-alone application

  3. An Object Model for a Rocket Engine Numerical Simulator

    NASA Technical Reports Server (NTRS)

    Mitra, D.; Bhalla, P. N.; Pratap, V.; Reddy, P.

    1998-01-01

    Rocket Engine Numerical Simulator (RENS) is a packet of software which numerically simulates the behavior of a rocket engine. Different parameters of the components of an engine is the input to these programs. Depending on these given parameters the programs output the behaviors of those components. These behavioral values are then used to guide the design of or to diagnose a model of a rocket engine "built" by a composition of these programs simulating different components of the engine system. In order to use this software package effectively one needs to have a flexible model of a rocket engine. These programs simulating different components then should be plugged into this modular representation. Our project is to develop an object based model of such an engine system. We are following an iterative and incremental approach in developing the model, as is the standard practice in the area of object oriented design and analysis of softwares. This process involves three stages: object modeling to represent the components and sub-components of a rocket engine, dynamic modeling to capture the temporal and behavioral aspects of the system, and functional modeling to represent the transformational aspects. This article reports on the first phase of our activity under a grant (RENS) from the NASA Lewis Research center. We have utilized Rambaugh's object modeling technique and the tool UML for this purpose. The classes of a rocket engine propulsion system are developed and some of them are presented in this report. The next step, developing a dynamic model for RENS, is also touched upon here. In this paper we will also discuss the advantages of using object-based modeling for developing this type of an integrated simulator over other tools like an expert systems shell or a procedural language, e.g., FORTRAN. Attempts have been made in the past to use such techniques.

  4. Simulations and model of the nonlinear Richtmyer–Meshkov instability

    DOE PAGES

    Dimonte, Guy; Ramaprabhu, P.

    2010-01-21

    The nonlinear evolution of the Richtmyer-Meshkov (RM) instability is investigated using numerical simulations with the FLASH code in two-dimensions (2D). The purpose of the simulations is to develop an empiricial nonlinear model of the RM instability that is applicable to inertial confinement fusion (ICF) and ejecta formation, namely, at large Atwood number A and scaled initial amplitude kho (k ≡ wavenumber) of the perturbation. The FLASH code is first validated with a variety of RM experiments that evolve well into the nonlinear regime. They reveal that bubbles stagnate when they grow by an increment of 2/k and that spikes acceleratemore » for A > 0.5 due to higher harmonics that focus them. These results are then compared with a variety of nonlinear models that are based on potential flow. We find that the models agree with simulations for moderate values of A < 0.9 and kho< 1, but not for the larger values that characterize ICF and ejecta formation. We thus develop a new nonlinear empirical model that captures the simulation results consistent with potential flow for a broader range of A and kho. Our hope is that such empirical models concisely capture the RM simulations and inspire more rigorous solutions.« less

  5. Simulations and model of the nonlinear Richtmyer–Meshkov instability

    SciTech Connect

    Dimonte, Guy; Ramaprabhu, P.

    2010-01-21

    The nonlinear evolution of the Richtmyer-Meshkov (RM) instability is investigated using numerical simulations with the FLASH code in two-dimensions (2D). The purpose of the simulations is to develop an empiricial nonlinear model of the RM instability that is applicable to inertial confinement fusion (ICF) and ejecta formation, namely, at large Atwood number A and scaled initial amplitude kho (k ≡ wavenumber) of the perturbation. The FLASH code is first validated with a variety of RM experiments that evolve well into the nonlinear regime. They reveal that bubbles stagnate when they grow by an increment of 2/k and that spikes accelerate for A > 0.5 due to higher harmonics that focus them. These results are then compared with a variety of nonlinear models that are based on potential flow. We find that the models agree with simulations for moderate values of A < 0.9 and kho< 1, but not for the larger values that characterize ICF and ejecta formation. We thus develop a new nonlinear empirical model that captures the simulation results consistent with potential flow for a broader range of A and kho. Our hope is that such empirical models concisely capture the RM simulations and inspire more rigorous solutions.

  6. Process Modeling and Dynamic Simulation for EAST Helium Refrigerator

    NASA Astrophysics Data System (ADS)

    Lu, Xiaofei; Fu, Peng; Zhuang, Ming; Qiu, Lilong; Hu, Liangbing

    2016-06-01

    In this paper, the process modeling and dynamic simulation for the EAST helium refrigerator has been completed. The cryogenic process model is described and the main components are customized in detail. The process model is controlled by the PLC simulator, and the realtime communication between the process model and the controllers is achieved by a customized interface. Validation of the process model has been confirmed based on EAST experimental data during the cool down process of 300-80 K. Simulation results indicate that this process simulator is able to reproduce dynamic behaviors of the EAST helium refrigerator very well for the operation of long pulsed plasma discharge. The cryogenic process simulator based on control architecture is available for operation optimization and control design of EAST cryogenic systems to cope with the long pulsed heat loads in the future. supported by National Natural Science Foundation of China (No. 51306195) and Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS (No. CRYO201408)

  7. Modeling the simulation execution process with digital objects

    NASA Astrophysics Data System (ADS)

    Cubert, Robert M.; Fishwick, Paul A.

    1999-06-01

    Object Oriented Physical Modeling (OOPM), formerly known as MOOSE, and its implementation of behavior multimodels provide an ability to manage arbitrarily complex patterns of behavioral abstraction in web-friendly simulation modeling. In an OOPM mode, one object stands as surrogate for another object, and these surrogates cognitively map to the real world. This `physical object' principle mitigates impact of incomplete knowledge and ambiguity because its real-world metaphors enable model authors to draw on intuition, facilitating reuse and integration, as well as consistency in collaborative efforts. A 3D interface for modeling and simulation visualization, under construction to augment the existing 2D GUI, obeys the physical object principle, providing a means to create, change, reuse, and integrate digital worlds made of digital objects. Implementation includes Distributed Simulation Executive, Digital object MultiModel Language, Digital Object Warehouse, and multimodel Translator. This approach is powerful and its capabilities have steadily grown; however, it has lacked a formal basis which we now provide: we define multimodels, represent digital objects as multimodels, transform multimodels to simulations, demonstrate the correctness of execution sequence of the simulations, and closure under coupling of digital objects. These theoretical results complement and enhance the practical aspects of physical multimodeling.

  8. Characterisation and modelling of brain tissue for surgical simulation.

    PubMed

    Mendizabal, A; Aguinaga, I; Sánchez, E

    2015-05-01

    Interactive surgical simulators capable of providing a realistic visual and haptic feedback to users are a promising technology for medical training and surgery planification. However, modelling the physical behaviour of human organs and tissues for surgery simulation remains a challenge. On the one hand, this is due to the difficulty to characterise the physical properties of biological soft tissues. On the other hand, the challenge still remains in the computation time requirements of real-time simulation required in interactive systems. Real-time surgical simulation and medical training must employ a sufficiently accurate and simple model of soft tissues in order to provide a realistic haptic and visual response. This study attempts to characterise the brain tissue at similar conditions to those that take place on surgical procedures. With this aim, porcine brain tissue is characterised, as a surrogate of human brain, on a rotational rheometer at low strain rates and large strains. In order to model the brain tissue with an adequate level of accuracy and simplicity, linear elastic, hyperelastic and quasi-linear viscoelastic models are defined. These models are simulated using the ABAQUS finite element platform and compared with the obtained experimental data.

  9. Modeling and simulation: A key to future defense technology

    NASA Technical Reports Server (NTRS)

    Muccio, Anthony B.

    1993-01-01

    The purpose of this paper is to express the rationale for continued technological and scientific development of the modeling and simulation process for the defense industry. The defense industry, along with a variety of other industries, is currently being forced into making sacrifices in response to the current economic hardships. These sacrifices, which may not compromise the safety of our nation, nor jeopardize our current standing as the world peace officer, must be concentrated in areas which will withstand the needs of the changing world. Therefore, the need for cost effective alternatives of defense issues must be examined. This paper provides support that the modeling and simulation process is an economically feasible process which will ensure our nation's safety as well as provide and keep up with the future technological developments and demands required by the defense industry. The outline of this paper is as follows: introduction, which defines and describes the modeling and simulation process; discussion, which details the purpose and benefits of modeling and simulation and provides specific examples of how the process has been successful; and conclusion, which summarizes the specifics of modeling and simulation of defense issues and lends the support for its continued use in the defense arena.

  10. A finite volume model simulation for the Broughton Archipelago, Canada

    NASA Astrophysics Data System (ADS)

    Foreman, M. G. G.; Czajko, P.; Stucchi, D. J.; Guo, M.

    A finite volume circulation model is applied to the Broughton Archipelago region of British Columbia, Canada and used to simulate the three-dimensional velocity, temperature, and salinity fields that are required by a companion model for sea lice behaviour, development, and transport. The absence of a high resolution atmospheric model necessitated the installation of nine weather stations throughout the region and the development of a simple data assimilation technique that accounts for topographic steering in interpolating/extrapolating the measured winds to the entire model domain. The circulation model is run for the period of March 13-April 3, 2008 and correlation coefficients between observed and model currents, comparisons between model and observed tidal harmonics, and root mean square differences between observed and model temperatures and salinities all showed generally good agreement. The importance of wind forcing in the near-surface circulation, differences between this simulation and one computed with another model, the effects of bathymetric smoothing on channel velocities, further improvements necessary for this model to accurately simulate conditions in May and June, and the implication of near-surface current patterns at a critical location in the 'migration corridor' of wild juvenile salmon, are also discussed.

  11. Midnight Temperature Maximum (MTM) in Whole Atmosphere Model (WAM) Simulations

    DTIC Science & Technology

    2016-04-14

    C. G. (1996), Simulations of the low -latitude midnight temperature maximum, J. Geophys. Res., 101, 26,863–26,874. Forbes, J. M., S. L. Bruinsma, Y...Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations R. A. Akmaev,1 F. Wu,2 T. J. Fuller-Rowell,2 and H. Wang2 Received 13...February 2009; accepted 18 March 2009; published 14 April 2009. [1] Discovered almost four decades ago, the midnight temperature maximum (MTM) with

  12. Modeling and Simulation of Plasma-Assisted Ignition and Combustion

    DTIC Science & Technology

    2013-10-01

    298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 School of Aerospace Engineering Air Plasma • self -consistent simulations of pulsed nanosecond... oxidation ns μs ms • quenching of excited species • ion recombination • gas heating • cumulative effects of multiple discharge pulses... Self -consistent simulations of pulsed nanosecond discharges in air with detailed kinetics. • Validation with experiments and analytical model results

  13. Strategic Implications of Cloud Computing for Modeling and Simulation (Briefing)

    DTIC Science & Technology

    2016-04-01

    et al, 2011]; Web - based [Brutzman et al, 2002]; HPC-based [Bouwens et al, 2012]), Grid-based [Pan et al, 2007]), technical exchanges with community...XMSF): Challenges for Web -Based Modeling and Simulation. Interim Technical Report. Monterey, CA: Naval Postgraduate School, 2002.  Cayirci, E...SCS M&S Magazine, 2010.  Henninger, A., Scrudder, R., Riggs, W., Wall, J., and Williams, K. (2016). “A Functional Deep Dive on Two Simulations

  14. Modeling and Simulation of Ceramic Arrays to Improve Ballistic Performance

    DTIC Science & Technology

    2014-03-01

    Unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Simulations were run on: -Monolithic AI5083 -Baseline -Proposed seam design of thickened edges...Proposed seam design of step ladder -Reasonable possible solution AutoDyn material properties may need to be adjusted to capture the full damage that...simulating and modeling the performance of ceramic/composite lightweight armor at seams and corners, and improving the armor’s performance in these regions

  15. Modeling and Simulation Tools for Heavy Lift Airships

    NASA Technical Reports Server (NTRS)

    Hochstetler, Ron; Chachad, Girish; Hardy, Gordon; Blanken, Matthew; Melton, John

    2016-01-01

    For conventional fixed wing and rotary wing aircraft a variety of modeling and simulation tools have been developed to provide designers the means to thoroughly investigate proposed designs and operational concepts. However, lighter-than-air (LTA) airships, hybrid air vehicles, and aerostats have some important aspects that are different from heavier-than-air (HTA) vehicles. In order to account for these differences, modifications are required to the standard design tools to fully characterize the LTA vehicle design and performance parameters.. To address these LTA design and operational factors, LTA development organizations have created unique proprietary modeling tools, often at their own expense. An expansion of this limited LTA tool set could be accomplished by leveraging existing modeling and simulation capabilities available in the National laboratories and public research centers. Development of an expanded set of publicly available LTA modeling and simulation tools for LTA developers would mitigate the reliance on proprietary LTA design tools in use today. A set of well researched, open source, high fidelity LTA design modeling and simulation tools would advance LTA vehicle development and also provide the analytical basis for accurate LTA operational cost assessments. This paper will present the modeling and analysis tool capabilities required for LTA vehicle design, analysis of operations, and full life-cycle support. A survey of the tools currently available will be assessed to identify the gaps between their capabilities and the LTA industry's needs. Options for development of new modeling and analysis capabilities to supplement contemporary tools will also be presented.

  16. Modeling the Lyα Forest in Collisionless Simulations

    NASA Astrophysics Data System (ADS)

    Sorini, Daniele; Oñorbe, José; Lukić, Zarija; Hennawi, Joseph F.

    2016-08-01

    Cosmological hydrodynamic simulations can accurately predict the properties of the intergalactic medium (IGM), but only under the condition of retaining the high spatial resolution necessary to resolve density fluctuations in the IGM. This resolution constraint prohibits simulating large volumes, such as those probed by BOSS and future surveys, like DESI and 4MOST. To overcome this limitation, we present “Iteratively Matched Statistics” (IMS), a novel method to accurately model the Lyα forest with collisionless N-body simulations, where the relevant density fluctuations are unresolved. We use a small-box, high-resolution hydrodynamic simulation to obtain the probability distribution function (PDF) and the power spectrum of the real-space Lyα forest flux. These two statistics are iteratively mapped onto a pseudo-flux field of an N-body simulation, which we construct from the matter density. We demonstrate that our method can reproduce the PDF, line of sight and 3D power spectra of the Lyα forest with good accuracy (7%, 4%, and 7% respectively). We quantify the performance of the commonly used Gaussian smoothing technique and show that it has significantly lower accuracy (20%-80%), especially for N-body simulations with achievable mean inter-particle separations in large-volume simulations. In addition, we show that IMS produces reasonable and smooth spectra, making it a powerful tool for modeling the IGM in large cosmological volumes and for producing realistic “mock” skies for Lyα forest surveys.

  17. Network simulation using the simulation language for alternate modeling (SLAM 2)

    NASA Technical Reports Server (NTRS)

    Shen, S.; Morris, D. W.

    1983-01-01

    The simulation language for alternate modeling (SLAM 2) is a general purpose language that combines network, discrete event, and continuous modeling capabilities in a single language system. The efficacy of the system's network modeling is examined and discussed. Examples are given of the symbolism that is used, and an example problem and model are derived. The results are discussed in terms of the ease of programming, special features, and system limitations. The system offers many features which allow rapid model development and provides an informative standardized output. The system also has limitations which may cause undetected errors and misleading reports unless the user is aware of these programming characteristics.

  18. Biomolecular simulation and modelling: status, progress and prospects

    PubMed Central

    van der Kamp, Marc W.; Shaw, Katherine E.; Woods, Christopher J.; Mulholland, Adrian J.

    2008-01-01

    Molecular simulation is increasingly demonstrating its practical value in the investigation of biological systems. Computational modelling of biomolecular systems is an exciting and rapidly developing area, which is expanding significantly in scope. A range of simulation methods has been developed that can be applied to study a wide variety of problems in structural biology and at the interfaces between physics, chemistry and biology. Here, we give an overview of methods and some recent developments in atomistic biomolecular simulation. Some recent applications and theoretical developments are highlighted. PMID:18611844

  19. Large Scale Simulations of the Kinetic Ising Model

    NASA Astrophysics Data System (ADS)

    Münkel, Christian

    We present Monte Carlo simulation results for the dynamical critical exponent z of the two- and three-dimensional kinetic Ising model. The z-values were calculated from the magnetization relaxation from an ordered state into the equilibrium state at Tc for very large systems with up to (169984)2 and (3072)3 spins. To our knowledge, these are the largest Ising-systems simulated todate. We also report the successful simulation of very large lattices on a massively parallel MIMD computer with high speedups of approximately 1000 and an efficiency of about 0.93.

  20. Digital quantum simulation of fermionic models with a superconducting circuit

    PubMed Central

    Barends, R.; Lamata, L.; Kelly, J.; García-Álvarez, L.; Fowler, A. G.; Megrant, A; Jeffrey, E; White, T. C.; Sank, D.; Mutus, J. Y.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Hoi, I.-C.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; Wenner, J.; Solano, E.; Martinis, John M.

    2015-01-01

    One of the key applications of quantum information is simulating nature. Fermions are ubiquitous in nature, appearing in condensed matter systems, chemistry and high energy physics. However, universally simulating their interactions is arguably one of the largest challenges, because of the difficulties arising from anticommutativity. Here we use digital methods to construct the required arbitrary interactions, and perform quantum simulation of up to four fermionic modes with a superconducting quantum circuit. We employ in excess of 300 quantum logic gates, and reach fidelities that are consistent with a simple model of uncorrelated errors. The presented approach is in principle scalable to a larger number of modes, and arbitrary spatial dimensions. PMID:26153660

  1. Digital quantum simulation of fermionic models with a superconducting circuit

    NASA Astrophysics Data System (ADS)

    Barends, R.; Lamata, L.; Kelly, J.; García-Álvarez, L.; Fowler, A. G.; Megrant, A.; Jeffrey, E.; White, T. C.; Sank, D.; Mutus, J. Y.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Hoi, I.-C.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; Wenner, J.; Solano, E.; Martinis, John M.

    2015-07-01

    One of the key applications of quantum information is simulating nature. Fermions are ubiquitous in nature, appearing in condensed matter systems, chemistry and high energy physics. However, universally simulating their interactions is arguably one of the largest challenges, because of the difficulties arising from anticommutativity. Here we use digital methods to construct the required arbitrary interactions, and perform quantum simulation of up to four fermionic modes with a superconducting quantum circuit. We employ in excess of 300 quantum logic gates, and reach fidelities that are consistent with a simple model of uncorrelated errors. The presented approach is in principle scalable to a larger number of modes, and arbitrary spatial dimensions.

  2. Development and testing of a mouse simulated space flight model

    NASA Technical Reports Server (NTRS)

    Sonnenfeld, G.

    1985-01-01

    The development and testing of a mouse model for simulating some aspects of weightlessness that occur during space flight, and the carrying out of immunological flight experiments on animals was discussed. The mouse model is an antiorthostatic, hypokinetic, hypodynamic suspension model similar to the one used with rats. It is shown that this murine model yield similar results to the rat model of antiorthostatic suspension for simulating some aspects of weightlessness. It is also shown that mice suspended in this model have decreased interferon-alpha/beta production as compared to control, nonsuspended mice or to orthostatically suspended mice. It is suggested that the conditions occuring during space flight could possibly affect interferon production. The regulatory role of interferon in nonviral diseases is demonstrated including several bacterial and protozoan infections indicating the great significance of interferon in resistance to many types of infectious diseases.

  3. A framework of modeling detector systems for computed tomography simulations

    NASA Astrophysics Data System (ADS)

    Youn, H.; Kim, D.; Kim, S. H.; Kam, S.; Jeon, H.; Nam, J.; Kim, H. K.

    2016-01-01

    Ultimate development in computed tomography (CT) technology may be a system that can provide images with excellent lesion conspicuity with the patient dose as low as possible. Imaging simulation tools have been cost-effectively used for these developments and will continue. For a more accurate and realistic imaging simulation, the signal and noise propagation through a CT detector system has been modeled in this study using the cascaded linear-systems theory. The simulation results are validated in comparisons with the measured results using a laboratory flat-panel micro-CT system. Although the image noise obtained from the simulations at higher exposures is slightly smaller than that obtained from the measurements, the difference between them is reasonably acceptable. According to the simulation results for various exposure levels and additive electronic noise levels, x-ray quantum noise is more dominant than the additive electronic noise. The framework of modeling a CT detector system suggested in this study will be helpful for the development of an accurate and realistic projection simulation model.

  4. Simulation Speed Analysis and Improvements of Modelica Models for Building Energy Simulation

    SciTech Connect

    Jorissen, Filip; Wetter, Michael; Helsen, Lieve

    2015-09-21

    This paper presents an approach for speeding up Modelica models. Insight is provided into how Modelica models are solved and what determines the tool’s computational speed. Aspects such as algebraic loops, code efficiency and integrator choice are discussed. This is illustrated using simple building simulation examples and Dymola. The generality of the work is in some cases verified using OpenModelica. Using this approach, a medium sized office building including building envelope, heating ventilation and air conditioning (HVAC) systems and control strategy can be simulated at a speed five hundred times faster than real time.

  5. Component and system simulation models for High Flux Isotope Reactor

    SciTech Connect

    Sozer, A.

    1989-08-01

    Component models for the High Flux Isotope Reactor (HFIR) have been developed. The models are HFIR core, heat exchangers, pressurizer pumps, circulation pumps, letdown valves, primary head tank, generic transport delay (pipes), system pressure, loop pressure-flow balance, and decay heat. The models were written in FORTRAN and can be run on different computers, including IBM PCs, as they do not use any specific simulation languages such as ACSL or CSMP. 14 refs., 13 figs.

  6. Exposing earth surface process model simulations to a large audience

    NASA Astrophysics Data System (ADS)

    Overeem, I.; Kettner, A. J.; Borkowski, L.; Russell, E. L.; Peddicord, H.

    2015-12-01

    The Community Surface Dynamics Modeling System (CSDMS) represents a diverse group of >1300 scientists who develop and apply numerical models to better understand the Earth's surface. CSDMS has a mandate to make the public more aware of model capabilities and therefore started sharing state-of-the-art surface process modeling results with large audiences. One platform to reach audiences outside the science community is through museum displays on 'Science on a Sphere' (SOS). Developed by NOAA, SOS is a giant globe, linked with computers and multiple projectors and can display data and animations on a sphere. CSDMS has developed and contributed model simulation datasets for the SOS system since 2014, including hydrological processes, coastal processes, and human interactions with the environment. Model simulations of a hydrological and sediment transport model (WBM-SED) illustrate global river discharge patterns. WAVEWATCH III simulations have been specifically processed to show the impacts of hurricanes on ocean waves, with focus on hurricane Katrina and super storm Sandy. A large world dataset of dams built over the last two centuries gives an impression of the profound influence of humans on water management. Given the exposure of SOS, CSDMS aims to contribute at least 2 model datasets a year, and will soon provide displays of global river sediment fluxes and changes of the sea ice free season along the Arctic coast. Over 100 facilities worldwide show these numerical model displays to an estimated 33 million people every year. Datasets storyboards, and teacher follow-up materials associated with the simulations, are developed to address common core science K-12 standards. CSDMS dataset documentation aims to make people aware of the fact that they look at numerical model results, that underlying models have inherent assumptions and simplifications, and that limitations are known. CSDMS contributions aim to familiarize large audiences with the use of numerical

  7. Simulation model air-to-air plate heat exchanger

    SciTech Connect

    Wetter, Michael

    1999-01-01

    A simple simulation model of an air-to-air plate heat exchanger is presented. The model belongs to a collection of simulation models that allows the eflcient computer simulation of heating, ventilation, and air-conditioning (HVAC) systems. The main emphasis of the models is to shorten computation time and to use only input data that are known in the design process of an HVAC system. The target of the models is to describe the behavior of HVAC components in the part-load operation mode, which is becoming increasingly important in energy eficient HVAC systems. The models are intended to be used for yearly energy calculations or load calculations with time steps of about 10 minutes or larger. Short- time dynamic effects, which are of interest for different aspects of control theory, are neglected. The part-load behavior is expressed in terms of the nominal condition and the dimensionless variation of the heat transfer with change of mass flow and temperature. The effectiveness- NTU relations are used to parametrize the convective heat transfer at nominal conditions and to compute the part-load condition. If the heat transfer coefficients on the two exchanger sides are not equal (i. e. due to partial bypassing of air), their ratio can be easily calculated and set as a parameter. The model is static and uses explicit equations only. The explicit model formulation ensures short computation time and numerical stability, which allows using the model with sophisticated engineering methods like automatic system optimization. This paper fully outlines the algorithm description and its simplifications. It is not tailored for any particular simulation program to ensure easy implementation in any simulation program.

  8. Hydrodynamic modeling of petroleum reservoirs using simulator MUFITS

    NASA Astrophysics Data System (ADS)

    Afanasyev, Andrey

    2015-04-01

    MUFITS is new noncommercial software for numerical modeling of subsurface processes in various applications (www.mufits.imec.msu.ru). To this point, the simulator was used for modeling nonisothermal flows in geothermal reservoirs and for modeling underground carbon dioxide storage. In this work, we present recent extension of the code to petroleum reservoirs. The simulator can be applied in conventional black oil modeling, but it also utilizes a more complicated models for volatile oil and gas condensate reservoirs as well as for oil rim fields. We give a brief overview of the code by providing the description of internal representation of reservoir models, which are constructed of grid blocks, interfaces, stock tanks as well as of pipe segments and pipe junctions for modeling wells and surface networks. For conventional black oil approach, we present the simulation results for SPE comparative tests. We propose an accelerated compositional modeling method for sub- and supercritical flows subjected to various phase equilibria, particularly to three-phase equilibria of vapour-liquid-liquid type. The method is based on the calculation of the thermodynamic potential of reservoir fluid as a function of pressure, total enthalpy and total composition and storing its values as a spline table, which is used in hydrodynamic simulation for accelerated PVT properties prediction. We provide the description of both the spline calculation procedure and the flashing algorithm. We evaluate the thermodynamic potential for a mixture of two pseudo-components modeling the heavy and light hydrocarbon fractions. We develop a technique for converting black oil PVT tables to the potential, which can be used for in-situ hydrocarbons multiphase equilibria prediction under sub- and supercritical conditions, particularly, in gas condensate and volatile oil reservoirs. We simulate recovery from a reservoir subject to near-critical initial conditions for hydrocarbon mixture. We acknowledge

  9. A future Outlook: Web based Simulation of Hydrodynamic models

    NASA Astrophysics Data System (ADS)

    Islam, A. S.; Piasecki, M.

    2003-12-01

    Despite recent advances to present simulation results as 3D graphs or animation contours, the modeling user community still faces some shortcomings when trying to move around and analyze data. Typical problems include the lack of common platforms with standard vocabulary to exchange simulation results from different numerical models, insufficient descriptions about data (metadata), lack of robust search and retrieval tools for data, and difficulties to reuse simulation domain knowledge. This research demonstrates how to create a shared simulation domain in the WWW and run a number of models through multi-user interfaces. Firstly, meta-datasets have been developed to describe hydrodynamic model data based on geographic metadata standard (ISO 19115) that has been extended to satisfy the need of the hydrodynamic modeling community. The Extended Markup Language (XML) is used to publish this metadata by the Resource Description Framework (RDF). Specific domain ontology for Web Based Simulation (WBS) has been developed to explicitly define vocabulary for the knowledge based simulation system. Subsequently, this knowledge based system is converted into an object model using Meta Object Family (MOF). The knowledge based system acts as a Meta model for the object oriented system, which aids in reusing the domain knowledge. Specific simulation software has been developed based on the object oriented model. Finally, all model data is stored in an object relational database. Database back-ends help store, retrieve and query information efficiently. This research uses open source software and technology such as Java Servlet and JSP, Apache web server, Tomcat Servlet Engine, PostgresSQL databases, Protégé ontology editor, RDQL and RQL for querying RDF in semantic level, Jena Java API for RDF. Also, we use international standards such as the ISO 19115 metadata standard, and specifications such as XML, RDF, OWL, XMI, and UML. The final web based simulation product is deployed as

  10. Flight Dynamics Modeling and Simulation of a Damaged Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Shah, Gautam H.; Hill, Melissa A.

    2012-01-01

    A study was undertaken at NASA Langley Research Center to establish, demonstrate, and apply methodology for modeling and implementing the aerodynamic effects of MANPADS damage to a transport aircraft into real-time flight simulation, and to demonstrate a preliminary capability of using such a simulation to conduct an assessment of aircraft survivability. Key findings from this study include: superpositioning of incremental aerodynamic characteristics to the baseline simulation aerodynamic model proved to be a simple and effective way of modeling damage effects; the primary effect of wing damage rolling moment asymmetry may limit minimum airspeed for adequate controllability, but this can be mitigated by the use of sideslip; combined effects of aerodynamics, control degradation, and thrust loss can result in significantly degraded controllability for a safe landing; and high landing speeds may be required to maintain adequate control if large excursions from the nominal approach path are allowed, but high-gain pilot control during landing can mitigate this risk.

  11. Gasification CFD Modeling for Advanced Power Plant Simulations

    SciTech Connect

    Zitney, S.E.; Guenther, C.P.

    2005-09-01

    In this paper we have described recent progress on developing CFD models for two commercial-scale gasifiers, including a two-stage, coal slurry-fed, oxygen-blown, pressurized, entrained-flow gasifier and a scaled-up design of the PSDF transport gasifier. Also highlighted was NETL’s Advanced Process Engineering Co-Simulator for coupling high-fidelity equipment models with process simulation for the design, analysis, and optimization of advanced power plants. Using APECS, we have coupled the entrained-flow gasifier CFD model into a coal-fired, gasification-based FutureGen power and hydrogen production plant. The results for the FutureGen co-simulation illustrate how the APECS technology can help engineers better understand and optimize gasifier fluid dynamics and related phenomena that impact overall power plant performance.

  12. Numerical simulation of turbomachinery flows with advanced turbulence models

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, B.; Kunz, R.; Luo, J.; Fan, S.

    1992-01-01

    A three dimensional full Navier-Stokes (FNS) code is used to simulate complex turbomachinery flows. The code incorporates an explicit multistep scheme and solves a conservative form of the density averaged continuity, momentum, and energy equations. A compressible low Reynolds number form of the k-epsilon turbulence model, and a q-omega model and an algebraic Reynolds stress model have been incorporated in a fully coupled manner to approximate Reynolds stresses. The code is used to predict the viscous flow field in a backswept transonic centrifugal compressor for which laser two focus data is available. The code is also used to simulate the tip clearance flow in a cascade. The code has been extended to include unsteady Euler solutions for predicting the unsteady flow through a cascade due to incoming wakes, simulating rotor-stator interactions.

  13. Computational challenges in modeling and simulating living matter

    NASA Astrophysics Data System (ADS)

    Sena, Alexandre C.; Silva, Dilson; Marzulo, Leandro A. J.; de Castro, Maria Clicia Stelling

    2016-12-01

    Computational modeling has been successfully used to help scientists understand physical and biological phenomena. Recent technological advances allowthe simulation of larger systems, with greater accuracy. However, devising those systems requires new approaches and novel architectures, such as the use of parallel programming, so that the application can run in the new high performance environments, which are often computer clusters composed of different computation devices, as traditional CPUs, GPGPUs, Xeon Phis and even FPGAs. It is expected that scientists take advantage of the increasing computational power to model and simulate more complex structures and even merge different models into larger and more extensive ones. This paper aims at discussing the challenges of using those devices to simulate such complex systems.

  14. Modeling and Simulating Blast Effects on Electric Substations

    SciTech Connect

    Lyle G. Roybal; Robert F. Jeffers; Kent E. McGillivary; Tony D. Paul; Ryan Jacobson

    2009-05-01

    A software simulation tool was developed at the Idaho National Laboratory to estimate the fragility of electric substation components subject to an explosive blast. Damage caused by explosively driven fragments on a generic electric substation was estimated by using a ray-tracing technique to track and tabulate fragment impacts and penetrations of substation components. This technique is based on methods used for assessing vulnerability of military aircraft and ground vehicles to explosive blasts. An open-source rendering and ray-trace engine was used for geometric modeling and interactions between fragments and substation components. Semi-empirical material interactions models were used to calculate blast parameters and simulate high-velocity material interactions between explosively driven fragments and substation components. Finally, a Monte Carlo simulation was added to model the random nature of fragment generation allowing a skilled analyst to predict failure probabilities of substation components.

  15. Model-based surgery simulation and intraoperational guidance

    NASA Astrophysics Data System (ADS)

    Kliegis, Ulrich G.; Zeilhofer, Hans-Florian U.; Gerhardt, Paul; Sader, Robert; Horch, Hans-Henning

    1997-05-01

    The transfer of the result of the surgical planning and simulation performed on an individual anatomical, CT based model onto the operation field is accomplished by fusing a live video image of the situs and a video image of the planning model, recorded rom the same relative camera location towards the anatomical structure. The surgeon can replicate the previously done simulation by guiding instruments like scalpels, bone saws, drills etc. along the markings left in the model. The visual superposition of the real and the synthetic world offers the surgeon an intuitively usable, tight link between the simulation stage and the real surgery. Osteotomy lines, the location of repositioned bone segments, implant positions and other relevant information are easily transferred in a non- invasive, non-tactile manner, thus reducing the risk of infection by reducing the count of foreign matter objects like templates, calipers, etc. brought into the situs.

  16. Charging effect simulation model used in simulations of plasma etching of silicon

    SciTech Connect

    Ishchuk, Valentyn; Volland, Burkhard E.; Hauguth, Maik; Rangelow, Ivo W.; Cooke, Mike

    2012-10-15

    Understanding the consequences of local surface charging on the evolving etching profile is a critical challenge in high density plasma etching. Deflection of the positively charged ions in locally varying electric fields can cause profile defects such as notching, bowing, and microtrenching. We have developed a numerical simulation model capturing the influence of the charging effect over the entire course of the etching process. The model is fully integrated into ViPER (Virtual Plasma Etch Reactor)-a full featured plasma processing simulation software developed at Ilmenau University of Technology. As a consequence, we show that local surface charge concurrently evolves with the feature profile to affect the final shape of the etched feature. Using gas chopping (sometimes called time-multiplexed) etch process for experimental validation of the simulation, we show that the model provides excellent fits to the experimental data and both, bowing and notching effects are captured-as long as the evolving profile and surface charge are simultaneously simulated. In addition, this new model explains that surface scallops, characteristic of gas chopping technique, are eroded and often absent in the final feature profile due to surface charging. The model is general and can be applied across many etching chemistries.

  17. Diagnostic and model dependent uncertainty of simulated Tibetan permafrost area

    USGS Publications Warehouse

    Wang, A.; Moore, J.C.; Cui, Xingquan; Ji, D.; Li, Q.; Zhang, N.; Wang, C.; Zhang, S.; Lawrence, D.M.; McGuire, A.D.; Zhang, W.; Delire, C.; Koven, C.; Saito, K.; MacDougall, A.; Burke, E.; Decharme, B.

    2016-01-01

     We perform a land-surface model intercomparison to investigate how the simulation of permafrost area on the Tibetan Plateau (TP) varies among six modern stand-alone land-surface models (CLM4.5, CoLM, ISBA, JULES, LPJ-GUESS, UVic). We also examine the variability in simulated permafrost area and distribution introduced by five different methods of diagnosing permafrost (from modeled monthly ground temperature, mean annual ground and air temperatures, air and surface frost indexes). There is good agreement (99 to 135  ×  104 km2) between the two diagnostic methods based on air temperature which are also consistent with the observation-based estimate of actual permafrost area (101  × 104 km2). However the uncertainty (1 to 128  ×  104 km2) using the three methods that require simulation of ground temperature is much greater. Moreover simulated permafrost distribution on the TP is generally only fair to poor for these three methods (diagnosis of permafrost from monthly, and mean annual ground temperature, and surface frost index), while permafrost distribution using air-temperature-based methods is generally good. Model evaluation at field sites highlights specific problems in process simulations likely related to soil texture specification, vegetation types and snow cover. Models are particularly poor at simulating permafrost distribution using the definition that soil temperature remains at or below 0 °C for 24 consecutive months, which requires reliable simulation of both mean annual ground temperatures and seasonal cycle, and hence is relatively demanding. Although models can produce better permafrost maps using mean annual ground temperature and surface frost index, analysis of simulated soil temperature profiles reveals substantial biases. The current generation of land-surface models need to reduce biases in simulated soil temperature profiles before reliable contemporary permafrost maps and predictions of changes in future

  18. Evaluating simulated functional trait patterns and quantifying modelled trait diversity effects on simulated ecosystem fluxes

    NASA Astrophysics Data System (ADS)

    Pavlick, R.; Schimel, D.

    2014-12-01

    Dynamic Global Vegetation Models (DGVMs) typically employ only a small set of Plant Functional Types (PFTs) to represent the vast diversity of observed vegetation forms and functioning. There is growing evidence, however, that this abstraction may not adequately represent the observed variation in plant functional traits, which is thought to play an important role for many ecosystem functions and for ecosystem resilience to environmental change. The geographic distribution of PFTs in these models is also often based on empirical relationships between present-day climate and vegetation patterns. Projections of future climate change, however, point toward the possibility of novel regional climates, which could lead to no-analog vegetation compositions incompatible with the PFT paradigm. Here, we present results from the Jena Diversity-DGVM (JeDi-DGVM), a novel traits-based vegetation model, which simulates a large number of hypothetical plant growth strategies constrained by functional tradeoffs, thereby allowing for a more flexible temporal and spatial representation of the terrestrial biosphere. First, we compare simulated present-day geographical patterns of functional traits with empirical trait observations (in-situ and from airborne imaging spectroscopy). The observed trait patterns are then used to improve the tradeoff parameterizations of JeDi-DGVM. Finally, focusing primarily on the simulated leaf traits, we run the model with various amounts of trait diversity. We quantify the effects of these modeled biodiversity manipulations on simulated ecosystem fluxes and stocks for both present-day conditions and transient climate change scenarios. The simulation results reveal that the coarse treatment of plant functional traits by current PFT-based vegetation models may contribute substantial uncertainty regarding carbon-climate feedbacks. Further development of trait-based models and further investment in global in-situ and spectroscopic plant trait observations

  19. Modeling, simulation, and experiments of coating growth on nanofibers

    NASA Astrophysics Data System (ADS)

    Clemons, C. B.; Hamrick, P.; Heminger, J.; Kreider, K. L.; Young, G. W.; Buldum, A.; Evans, E.; Zhang, G.

    2008-02-01

    This work is a comparison of modeling and simulation results with experiments for an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor level, nanofiber level and atomic level to form a comprehensive model. The comprehensive model leads to the definition of an evolution equation for the coating free surface around an isolated nanofiber. This evolution equation was previously derived and solved under conditions of a nearly circular coating, with a concentration field that was only radially dependent and that was independent of the location of the coating free surface. These assumptions permitted the development of analytical expressions for the concentration field. The present work does not impose the above-mentioned conditions and considers numerical simulations of the concentration field that couple with level set simulations of the evolution equation for the coating free surface. Further, the cases of coating an isolated fiber as well as a multiple fiber mat are considered. Simulation results are compared with experimental results as the reactor pressure and power, as well as the nanofiber mat porosity, are varied.

  20. Numerical simulations of altocumulus with a cloud resolving model

    SciTech Connect

    Liu, S.; Krueger, S.K.

    1996-04-01

    Altocumulus and altostratus clouds together cover approximately 22% of the earth`s surface. They play an important role in the earth`s energy budget through their effect on solar and infrared radiation. However, there has been little altocumulus cloud investigation by either modelers or observational programs. Starr and Cox (SC) (1985a,b) simulated an altostratus case as part of the same study in which they modeled a thin layer of cirrus. Although this calculation was originally described as representing altostratus, it probably better represents altocumulus stratiformis. In this paper, we simulate altocumulus cloud with a cloud resolving model (CRM). We simply describe the CRM first. We calculate the same middle-level cloud case as SC to compare our results with theirs. We will look at the role of cloud-scale processes in response to large-scale forcing. We will also discuss radiative effects by simulating diurnal and nocturnal cases. Finally, we discuss the utility of a 1D model by comparing 1D simulations and 2D simulations.

  1. Modeling and HIL Simulation of Flight Conditions Simulating Control System for the Altitude Test Facility

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Shen, Li; Zhang, Tianhong

    2016-12-01

    Simulated altitude test is an essential exploring, debugging, verification and validation means during the development of aero-engine. Free-jet engine test can simulate actual working conditions of aero-engine more realistically than direct-connect engine test but with relatively lower cost compared to propulsion wind tunnel test, thus becoming an important developing area of simulated altitude test technology. The Flight Conditions Simulating Control System (FCSCS) is of great importance to the Altitude Test Facility (ATF) but the development of that is a huge challenge. Aiming at improving the design efficiency and reducing risks during the development of FCSCS for ATFs, a Hardware- in-the-Loop (HIL) simulation system was designed and the mathematical models of key components such as the pressure stabilizing chamber, free-jet nozzle, control valve and aero-engine were built in this paper. Moreover, some HIL simulation experiments were carried out. The results show that the HIL simulation system designed and established in this paper is reasonable and effective, which can be used to adjust control parameters conveniently and assess the software and hardware in the control system immediately.

  2. Arctic Ocean Freshwater: How Robust are Model Simulations

    NASA Technical Reports Server (NTRS)

    Jahn, A.; Aksenov, Y.; deCuevas, B. A.; deSteur, L.; Haekkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; Lique, C.; Nguyen, A.; Pemberton, P.; Worthen, D.; Zhang, J.

    2012-01-01

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.

  3. Simulation models in population breast cancer screening: A systematic review.

    PubMed

    Koleva-Kolarova, Rositsa G; Zhan, Zhuozhao; Greuter, Marcel J W; Feenstra, Talitha L; De Bock, Geertruida H

    2015-08-01

    The aim of this review was to critically evaluate published simulation models for breast cancer screening of the general population and provide a direction for future modeling. A systematic literature search was performed to identify simulation models with more than one application. A framework for qualitative assessment which incorporated model type; input parameters; modeling approach, transparency of input data sources/assumptions, sensitivity analyses and risk of bias; validation, and outcomes was developed. Predicted mortality reduction (MR) and cost-effectiveness (CE) were compared to estimates from meta-analyses of randomized control trials (RCTs) and acceptability thresholds. Seven original simulation models were distinguished, all sharing common input parameters. The modeling approach was based on tumor progression (except one model) with internal and cross validation of the resulting models, but without any external validation. Differences in lead times for invasive or non-invasive tumors, and the option for cancers not to progress were not explicitly modeled. The models tended to overestimate the MR (11-24%) due to screening as compared to optimal RCTs 10% (95% CI - 2-21%) MR. Only recently, potential harms due to regular breast cancer screening were reported. Most scenarios resulted in acceptable cost-effectiveness estimates given current thresholds. The selected models have been repeatedly applied in various settings to inform decision making and the critical analysis revealed high risk of bias in their outcomes. Given the importance of the models, there is a need for externally validated models which use systematical evidence for input data to allow for more critical evaluation of breast cancer screening.

  4. a Discrete Mathematical Model to Simulate Malware Spreading

    NASA Astrophysics Data System (ADS)

    Del Rey, A. Martin; Sánchez, G. Rodriguez

    2012-10-01

    With the advent and worldwide development of Internet, the study and control of malware spreading has become very important. In this sense, some mathematical models to simulate malware propagation have been proposed in the scientific literature, and usually they are based on differential equations exploiting the similarities with mathematical epidemiology. The great majority of these models study the behavior of a particular type of malware called computer worms; indeed, to the best of our knowledge, no model has been proposed to simulate the spreading of a computer virus (the traditional type of malware which differs from computer worms in several aspects). In this sense, the purpose of this work is to introduce a new mathematical model not based on continuous mathematics tools but on discrete ones, to analyze and study the epidemic behavior of computer virus. Specifically, cellular automata are used in order to design such model.

  5. Acoustic performance of industrial mufflers with CAE modeling and simulation

    NASA Astrophysics Data System (ADS)

    Jeon, Soohong; Kim, Daehwan; Hong, Chinsuk; Jeong, Weuibong

    2014-12-01

    This paper investigates the noise transmission performance of industrial mufflers widely used in ships based on the CAE modeling and simulation. Since the industrial mufflers have very complicated internal structures, the conventional Transfer Matrix Method (TMM) is of limited use. The CAE modeling and simulation is therefore required to incorporate commercial softwares: CATIA for geometry modeling, MSC/PATRAN for FE meshing and LMS/ SYSNOISE for analysis. Main sources of difficulties in this study are led by complicated arrangement of reactive elements, perforated walls and absorption materials. The reactive elements and absorbent materials are modeled by applying boundary conditions given by impedance. The perforated walls are modeled by applying the transfer impedance on the duplicated node mesh. The CAE approach presented in this paper is verified by comparing with the theoretical solution of a concentric-tube resonator and is applied for industrial mufflers.

  6. Hierarchical simulation of aquifer heterogeneity: implications of different simulation settings on solute-transport modeling

    NASA Astrophysics Data System (ADS)

    Comunian, Alessandro; De Micheli, Leonardo; Lazzati, Claudio; Felletti, Fabrizio; Giacobbo, Francesca; Giudici, Mauro; Bersezio, Riccardo

    2016-03-01

    The fine-scale heterogeneity of porous media affects the large-scale transport of solutes and contaminants in groundwater and it can be reproduced by means of several geostatistical simulation tools. However, including the available geological information in these tools is often cumbersome. A hierarchical simulation procedure based on a binary tree is proposed and tested on two real-world blocks of alluvial sediments, of a few cubic meters volume, that represent small-scale aquifer analogs. The procedure is implemented using the sequential indicator simulation, but it is so general that it can be adapted to various geostatistical simulation tools, improving their capability to incorporate geological information, i.e., the sedimentological and architectural characterization of heterogeneity. When compared with a standard sequential indicator approach on bi-dimensional simulations, in terms of proportions and connectivity indicators, the proposed procedure yields reliable results, closer to the reference observations. Different ensembles of three-dimensional simulations based on different hierarchical sequences are used to perform numerical experiments of conservative solute transport and to obtain ensembles of equivalent pore velocity and dispersion coefficient at the scale length of the blocks (meter). Their statistics are used to estimate the impact of the variability of the transport properties of the simulated blocks on contaminant transport modeled on bigger domains (hectometer). This is investigated with a one-dimensional transport modeling based on the Kolmogorov-Dmitriev theory of branching stochastic processes. Applying the proposed approach with diverse binary trees and different simulation settings provides a great flexibility, which is revealed by the differences in the breakthrough curves.

  7. Estimation of the parameters of ETAS models by Simulated Annealing.

    PubMed

    Lombardi, Anna Maria

    2015-02-12

    This paper proposes a new algorithm to estimate the maximum likelihood parameters of an Epidemic Type Aftershock Sequences (ETAS) model. It is based on Simulated Annealing, a versatile method that solves problems of global optimization and ensures convergence to a global optimum. The procedure is tested on both simulated and real catalogs. The main conclusion is that the method performs poorly as the size of the catalog decreases because the effect of the correlation of the ETAS parameters is more significant. These results give new insights into the ETAS model and the efficiency of the maximum-likelihood method within this context.

  8. Estimation of the parameters of ETAS models by Simulated Annealing

    NASA Astrophysics Data System (ADS)

    Lombardi, Anna Maria

    2015-02-01

    This paper proposes a new algorithm to estimate the maximum likelihood parameters of an Epidemic Type Aftershock Sequences (ETAS) model. It is based on Simulated Annealing, a versatile method that solves problems of global optimization and ensures convergence to a global optimum. The procedure is tested on both simulated and real catalogs. The main conclusion is that the method performs poorly as the size of the catalog decreases because the effect of the correlation of the ETAS parameters is more significant. These results give new insights into the ETAS model and the efficiency of the maximum-likelihood method within this context.

  9. Estimation of the parameters of ETAS models by Simulated Annealing

    PubMed Central

    Lombardi, Anna Maria

    2015-01-01

    This paper proposes a new algorithm to estimate the maximum likelihood parameters of an Epidemic Type Aftershock Sequences (ETAS) model. It is based on Simulated Annealing, a versatile method that solves problems of global optimization and ensures convergence to a global optimum. The procedure is tested on both simulated and real catalogs. The main conclusion is that the method performs poorly as the size of the catalog decreases because the effect of the correlation of the ETAS parameters is more significant. These results give new insights into the ETAS model and the efficiency of the maximum-likelihood method within this context. PMID:25673036

  10. Control design and simulation of systems modeled using ADAMS

    NASA Technical Reports Server (NTRS)

    Sohoni, Vikram N.

    1989-01-01

    A technique for control design and simulation using the ADAMS software and a control design software package is presented. For design of control systems ADAMS generates a minimum realization linear time invariant (LTI), state space representation of multi-body models. This LTI representation can be produced in formats for input to several commercial control design packages. The user can exercise various design strategies in the control design software to arrive at a suitable compensator. The resulting closed loop model can then be simulated using ADAMS. This procedure is illustrated with two examples.

  11. Modeling and Simulation For A Variable Sprayerrate System

    NASA Astrophysics Data System (ADS)

    Shi, Yan; Liang, Anbo; Yuan, Haibo; Zhang, Chunmei; Li, Junlong

    Variable spraying technology is an important content and developing direction in current plant protection machinery, which can effectively save pesticide and lighten burden of ecological environment in agriculture according to characteristic of spraying targets and speed of aircraft crew. Paper established mathematic model and delivery function of variable spraying system based on designed hardware of variable spraying machine, making use of PID controlling algorithm to simulate in MATLAB. Simulating result explained that the model can conveniently control gushing amounts and can arrive at satisfied controlling.

  12. Modeling and Simulation For A Variable Sprayerrate System

    NASA Astrophysics Data System (ADS)

    Shi, Yan; Liang, Anbo; Yuan, Haibo; Zhang, Chunmei; Li, Junlong

    Variable spraying technology is an important content and developing direction in current plant protection machinery, which can effectively save pesticide and lighten burden of ecological environment in agriculture according to characteristic of spraying targets and speed of aircraft crew. Paper established mathematic model and delivery function of variable spraying system based on designed hardware of variable spraying machine, making use of PID controlling algorithm to simulate in matlab. Simulating result explained that the model can conveniently control gushing amounts and can arrive at satisfied controlling.

  13. Numerical simulation model for vertical flow in geothermal wells

    SciTech Connect

    Tachimori, M.

    1982-01-01

    A numerical simulation model for vertical flow in geothermal wells is presented. The model consists of equations for the conservation of mass, momentum, and energy, for thermodynamic state of water, for friction losses, for slip velocity relations, and of the criteria for various flow regimes. A new set of correlations and criteria is presented for two-phase flow to improve the accuracy of predictions; bubbly flow - Griffith and Wallis correlation, slug flow - Nicklin et al. one, annular-mist flow - Inoue and Aoki and modified by the author. The simulation method was verified by data from actual wells.

  14. Equatorial waves simulated by the NCAR community climate model

    NASA Technical Reports Server (NTRS)

    Cheng, Xinhua; Chen, Tsing-Chang

    1988-01-01

    The equatorial planetary waves simulated by the NCAR CCM1 general circulation model were investigated in terms of space-time spectral analysis (Kao, 1968; Hayashi, 1971, 1973) and energetic analysis (Hayashi, 1980). These analyses are particularly applied to grid-point data on latitude circles. In order to test some physical factors which may affect the generation of tropical transient planetary waves, three different model simulations with the CCM1 (the control, the no-mountain, and the no-cloud experiments) were analyzed.

  15. A Software Development Simulation Model of a Spiral Process

    NASA Technical Reports Server (NTRS)

    Mizell, Carolyn; Malone, Linda

    2007-01-01

    There is a need for simulation models of software development processes other than the waterfall because processes such as spiral development are becoming more and more popular. The use of a spiral process can make the inherently difficult job of cost and schedule estimation even more challenging due to its evolutionary nature, but this allows for a more flexible process that can better meet customers' needs. This paper will present a discrete event simulation model of spiral development that can be used to analyze cost and schedule effects of using such a process in comparison to a waterfall process.

  16. The ``caterpillar'' simulation model for a biological filament

    NASA Astrophysics Data System (ADS)

    Bailey, Aimee; Lowe, Christopher; Sutton, Adrian

    2009-03-01

    We present a simulation model for an elastic filament in a viscous fluid, relevant for systems ranging from suspensions of paper pulp to micro-organism motility. It incorporates the Stokeslet treatment of the hydrodynamic force. We show that a non-arbitrary choice of the hydrodynamic radius is necessary to recover known dynamic behavior of a fiber with a finite cross-section. Our simulations explore configurations inaccessible by theory. We illustrate the utility of the model by considering the simple scenario of a charged filament in an electric field. Results suggest a circularly polarized electric field is a viable means for aligning microtubules in solution.

  17. Role of modeling and simulation in pediatric investigation plans.

    PubMed

    Manolis, Efthymios; Osman, Tariq Eldirdiry; Herold, Ralf; Koenig, Franz; Tomasi, Paolo; Vamvakas, Spiros; Saint Raymond, Agnes

    2011-03-01

    Ethical and practical constraints encourage the optimal use of resources in pediatric drug development. Modeling and simulation has emerged as a promising methodology acknowledged by industry, academia, and regulators. We previously proposed a paradigm in pediatric drug development, whereby modeling and simulation is used as a decision tool, for study optimization and/or as a data analysis tool. Three and a half years since the Paediatric Regulation came into force in 2007, the European Medicines Agency has gained substantial experience in the use of modeling and simulation in pediatric drug development. In this review, we present examples on how the proposed paradigm applies in real case scenarios of planned pharmaceutical developments. We also report the results of a pediatric database search to further 'validate' the paradigm. There were 47 of 210 positive pediatric investigation plan (PIP) opinions that made reference to modeling and simulation (data included all positive opinions issued up to January 2010). This reflects a major shift in regulatory thinking. The ratio of PIPs with modeling and simulation rose to two in five based on the summary reports. Population pharmacokinetic (POP-PK) and pharmacodynamics (POP-PD) and physiologically based pharmacokinetic models are widely used by industry and endorsed or even imposed by regulators as a way to circumvent some difficulties in developing medicinal products in children. The knowledge of the effects of age and size on PK is improving, and models are widely employed to make optimal use of this knowledge but less is known about the effects of size and maturation on PD, disease progression, and safety. Extrapolation of efficacy from different age groups is often used in pediatric medicinal development as another means to alleviate the burden of clinical trials in children, and this can be aided by modeling and simulation to supplement clinical data. The regulatory assessment is finally judged on clinical grounds

  18. Thermochemistry Models Applicable to a Vectorized Particle Simulation

    NASA Astrophysics Data System (ADS)

    Haas, Brian Lee

    1991-02-01

    The finite rates of reactions and thermal excitation processes in a gas result in thermochemical non-equilibrium in the hypersonic rarefied flowfield associated with vehicles during atmospheric entry. The low-density nature of this flow is such that the familiar Navier-Stokes equations are not applicable. Alternatively, particle simulation methods circumvent the difficulties of rarefaction by modeling the gas as a collection of moving and colliding particles in accordance with the principles of kinetic theory and statistical mechanics. The Direct Simulation Monte Carlo (DSMC) method of Bird has been applied extensively but is limited by excessive computational expense. An alternative particle simulation, tailored specifically to the vector-processing architecture of modern supercomputers, has been developed by Baganoff and McDonald to optimize computational performance in modeling the three-dimensional non-reactive flow of general gas mixtures including simple models for rotational and vibrational relaxation. The objective of this thesis is to extend the vectorized simulation to treat chemically reactive flows and to enhance the models for vibrational relaxation. A collision selection rule has been developed to yield vibrational relaxation rates which match the experimental fits of Millikan and White. Selection rules for dissociation, atomic exchange, and recombination reactions were developed to yield reaction rates which match those dictated by the Arrhenius experimental fits over the temperature range of interest. The vibrational relaxation mechanics model of McDonald was modified for application to both the simple harmonic and anharmonic oscillator descriptions of the quantized vibrational mode. Reaction mechanics are modeled by proportional addition or removal of reaction energy from each contributing mode in a collision. All of these models retain computational simplicity while satisfying detailed balance and promoting equilibrium. An improved reaction model

  19. A simulation model of water depth in mangrove basin forests.

    PubMed

    Ritchie, S A

    1990-06-01

    The construction and validation of a model simulating the water depth within mangrove basin forests is described. Rainfall, water table, water depth and tide data collected from a red mangrove basin forest on Marco Island, FL, was used to estimate model parameters. These included the basin spillover height, evapotranspiration-infiltration rate and the functional relationship of water depth change to rainfall, tide and basin spillover. The model was constructed with LOTUS 123 and calibrated from staff gauge water depth records. The model proved accurate and adaptable. Water depths from the model and staff gauge were correlated highly (r = 0.98). Data from an adjacent black mangrove forest featuring complex wet-dry cycling were used to modify the model. After calibration, the model provided an accurate record of water depths at the site (r = 0.89). This model will provide water depths used in a model of Aedes taeniorhynchus population dynamics.

  20. Models and Simulations as a Service: Exploring the Use of Galaxy for Delivering Computational Models

    PubMed Central

    Walker, Mark A.; Madduri, Ravi; Rodriguez, Alex; Greenstein, Joseph L.; Winslow, Raimond L.

    2016-01-01

    We describe the ways in which Galaxy, a web-based reproducible research platform, can be used for web-based sharing of complex computational models. Galaxy allows users to seamlessly customize and run simulations on cloud computing resources, a concept we refer to as Models and Simulations as a Service (MaSS). To illustrate this application of Galaxy, we have developed a tool suite for simulating a high spatial-resolution model of the cardiac Ca2+ spark that requires supercomputing resources for execution. We also present tools for simulating models encoded in the SBML and CellML model description languages, thus demonstrating how Galaxy’s reproducible research features can be leveraged by existing technologies. Finally, we demonstrate how the Galaxy workflow editor can be used to compose integrative models from constituent submodules. This work represents an important novel approach, to our knowledge, to making computational simulations more accessible to the broader scientific community. PMID:26958881

  1. Simulations of Aerosol Microphysics in the NASA GEOS-5 Model

    NASA Technical Reports Server (NTRS)

    Colarco, Peter; Smith; Randles; daSilva

    2010-01-01

    Aerosol-cloud-chemistry interactions have potentially large but uncertain impacts on Earth's climate. One path to addressing these uncertainties is to construct models that incorporate various components of the Earth system and to test these models against data. To that end, we have previously incorporated the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module online in the NASA Goddard Earth Observing System model (GEOS-5). GEOS-5 provides a platform for Earth system modeling, incorporating atmospheric and ocean general circulation models, a land surface model, a data assimilation system, and treatments of atmospheric chemistry and hydrologic cycle. Including GOCART online in this framework has provided a path for interactive aerosol-climate studies; however, GOCART only tracks the mass of aerosols as external mixtures and does not include the detailed treatments of aerosol size distribution and composition (internal mixtures) needed for aerosol-cloud-chemistry-climate studies. To address that need we have incorporated the Community Aerosol and Radiation Model for Atmospheres (CARMA) online in GEOS-5. CARMA is a sectional aerosol-cloud microphysical model, capable of treating both aerosol size and composition explicitly be resolving the aerosol distribution into a variable number of size and composition groupings. Here we present first simulations of dust, sea salt, and smoke aerosols in GEOS-5 as treated by CARMA. These simulations are compared to available aerosol satellite, ground, and aircraft data and as well compared to the simulated distributions in our current GOCART based system.

  2. Benchmarking computational fluid dynamics models for lava flow simulation

    NASA Astrophysics Data System (ADS)

    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi

    2016-04-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, and COMSOL. Using the new benchmark scenarios defined in Cordonnier et al. (Geol Soc SP, 2015) as a guide, we model viscous, cooling, and solidifying flows over horizontal and sloping surfaces, topographic obstacles, and digital elevation models of natural topography. We compare model results to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We can apply these models to reconstruct past lava flows in Hawai'i and Saudi Arabia using parameters assembled from morphology, textural analysis, and eruption observations as natural test cases. Our study highlights the strengths and weaknesses of each code, including accuracy and computational costs, and provides insights regarding code selection.

  3. Biocellion: accelerating computer simulation of multicellular biological system models

    PubMed Central

    Kang, Seunghwa; Kahan, Simon; McDermott, Jason; Flann, Nicholas; Shmulevich, Ilya

    2014-01-01

    Motivation: Biological system behaviors are often the outcome of complex interactions among a large number of cells and their biotic and abiotic environment. Computational biologists attempt to understand, predict and manipulate biological system behavior through mathematical modeling and computer simulation. Discrete agent-based modeling (in combination with high-resolution grids to model the extracellular environment) is a popular approach for building biological system models. However, the computational complexity of this approach forces computational biologists to resort to coarser resolution approaches to simulate large biological systems. High-performance parallel computers have the potential to address the computing challenge, but writing efficient software for parallel computers is difficult and time-consuming. Results: We have developed Biocellion, a high-performance software framework, to solve this computing challenge using parallel computers. To support a wide range of multicellular biological system models, Biocellion asks users to provide their model specifics by filling the function body of pre-defined model routines. Using Biocellion, modelers without parallel computing expertise can efficiently exploit parallel computers with less effort than writing sequential programs from scratch. We simulate cell sorting, microbial patterning and a bacterial system in soil aggregate as case studies. Availability and implementation: Biocellion runs on x86 compatible systems with the 64 bit Linux operating system and is freely available for academic use. Visit http://biocellion.com for additional information. Contact: seunghwa.kang@pnnl.gov PMID:25064572

  4. The medical simulation markup language - simplifying the biomechanical modeling workflow.

    PubMed

    Suwelack, Stefan; Stoll, Markus; Schalck, Sebastian; Schoch, Nicolai; Dillmann, Rüdiger; Bendl, Rolf; Heuveline, Vincent; Speidel, Stefanie

    2014-01-01

    Modeling and simulation of the human body by means of continuum mechanics has become an important tool in diagnostics, computer-assisted interventions and training. This modeling approach seeks to construct patient-specific biomechanical models from tomographic data. Usually many different tools such as segmentation and meshing algorithms are involved in this workflow. In this paper we present a generalized and flexible description for biomechanical models. The unique feature of the new modeling language is that it not only describes the final biomechanical simulation, but also the workflow how the biomechanical model is constructed from tomographic data. In this way, the MSML can act as a middleware between all tools used in the modeling pipeline. The MSML thus greatly facilitates the prototyping of medical simulation workflows for clinical and research purposes. In this paper, we not only detail the XML-based modeling scheme, but also present a concrete implementation. Different examples highlight the flexibility, robustness and ease-of-use of the approach.

  5. Modelling and simulation of substrate elasticity sensing in stem cells.

    PubMed

    Zeng, Xiaowei; Li, Shaofan

    2011-05-01

    Recently, we have developed a multiscale soft matter cell model aiming at improving the understanding of mechanotransduction mechanism of stem cells, which is responsible for information exchange between cells and their extracellular environment. In this paper, we report the preliminary results of our research on multiscale modelling and simulation of soft contact and adhesion of stem cells. The proposed multiscale soft matter cell model may be used to model soft contact and adhesion between cells and their extracellular substrates. To the authors' best knowledge, this may be the first time that a soft matter model has been developed for cell contact and adhesion. Moreover, we have developed and implemented a Lagrange-type meshfree Galerkin formulation and related computational algorithms for the proposed cell model. Comparison study with experimental data has been conducted to validate the parameters of the cell model. By using the soft matter cell model, we have simulated the soft adhesive contact process between cells and extracellular substrates. The simulation shows that the cell can sense substrate elasticity by responding it in different manners from cell spreading to cell contact configuration and molecular conformation changes.

  6. Knowledge representation and qualitative simulation of salmon redd functioning. Part I: qualitative modeling and simulation.

    PubMed

    Guerrin, F; Dumas, J

    2001-02-01

    This work aims at representing empirical knowledge of freshwater ecologists on the functioning of salmon redds (spawning areas of salmon) and its impact on mortality of early stages. For this, we use Qsim, a qualitative simulator. In this first part, we provide unfamiliar readers with the underlying qualitative differential equation (QDE) ontology of Qsim: representing quantities, qualitative variables, qualitative constraints, QDE structure. Based on a very simple example taken of the salmon redd application, we show how informal biological knowledge may be represented and simulated using an approach that was first intended to analyze qualitatively ordinary differential equations systems. A companion paper (Part II) gives the full description and simulation of the salmon redd qualitative model. This work was part of a project aimed at assessing the impact of the environment on salmon populations dynamics by the use of models of processes acting at different levels: catchment, river, and redds. Only the latter level is dealt with in this paper.

  7. Off-gas adsorption model and simulation - OSPREY

    SciTech Connect

    Rutledge, V.J.

    2013-07-01

    A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes is expected to provide substantial cost savings and many technical benefits. To support this capability, a modeling effort focused on the off-gas treatment system of a used nuclear fuel recycling facility is in progress. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and Recovery (OSPREY) models the adsorption of offgas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas composition, sorbent and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data can be obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. In addition to concentration data, the model predicts temperature along the column length as a function of time and pressure drop along the column length. A description of the OSPREY model, results from krypton adsorption modeling and plans for modeling the behavior of iodine, xenon, and tritium will be discussed. (author)

  8. Automated Environmental Simulation Model Tor Analyzing Wound Fiber Optic Bobbins

    NASA Astrophysics Data System (ADS)

    Edwards, Eugene; Ruffin, Paul B.

    1987-01-01

    The life of optical fibers under stress for an extended period of time is limited by static fatigue caused by stress corrosion in the presence of moisture. In order to predict the life of wound optical fibers, it is necessary to accelerate the aging process by simulating the storage environment (stress, temperature, and humidity) in a short period of time. Existing environmental test systems have been proven useful in the simulation of the storage environment; however, the data is limited due to the manual mode of operation. An automated environmental simulation model is developed to control, collect, process, and analyze optical loss data while measuring temperature and humidity. The environmental conditions for optical fibers wound for various applications are simulated in order to understand the interrelationships between wound fiber parameters including spool composition/design, winding tension, adhesives, and fiber cable design. Experimental investigations are carried out to expose wound optical fiber to simulated environments while monitoring changes in the optical and mechanical characteristics of the fibers. Based on the preliminary results of the data obtained, the automated simulation system is proven acceptable for performing routine modeling and evaluations. The automated system is a valuable instrument to aid in the characterization of optical fibers.

  9. Lattice Boltzmann modeling of directional wetting: Comparing simulations to experiments

    NASA Astrophysics Data System (ADS)

    Jansen, H. Patrick; Sotthewes, Kai; van Swigchem, Jeroen; Zandvliet, Harold J. W.; Kooij, E. Stefan

    2013-07-01

    Lattice Boltzmann Modeling (LBM) simulations were performed on the dynamic behavior of liquid droplets on chemically striped patterned surfaces, ultimately with the aim to develop a predictive tool enabling reliable design of future experiments. The simulations accurately mimic experimental results, which have shown that water droplets on such surfaces adopt an elongated shape due to anisotropic preferential spreading. Details of the contact line motion such as advancing of the contact line in the direction perpendicular to the stripes exhibit pronounced similarities in experiments and simulations. The opposite of spreading, i.e., evaporation of water droplets, leads to a characteristic receding motion first in the direction parallel to the stripes, while the contact line remains pinned perpendicular to the stripes. Only when the aspect ratio is close to unity, the contact line also starts to recede in the perpendicular direction. Very similar behavior was observed in the LBM simulations. Finally, droplet movement can be induced by a gradient in surface wettability. LBM simulations show good semiquantitative agreement with experimental results of decanol droplets on a well-defined striped gradient, which move from high- to low-contact angle surfaces. Similarities and differences for all systems are described and discussed in terms of the predictive capabilities of LBM simulations to model direction wetting.

  10. Lattice Boltzmann modeling of directional wetting: comparing simulations to experiments.

    PubMed

    Jansen, H Patrick; Sotthewes, Kai; van Swigchem, Jeroen; Zandvliet, Harold J W; Kooij, E Stefan

    2013-07-01

    Lattice Boltzmann Modeling (LBM) simulations were performed on the dynamic behavior of liquid droplets on chemically striped patterned surfaces, ultimately with the aim to develop a predictive tool enabling reliable design of future experiments. The simulations accurately mimic experimental results, which have shown that water droplets on such surfaces adopt an elongated shape due to anisotropic preferential spreading. Details of the contact line motion such as advancing of the contact line in the direction perpendicular to the stripes exhibit pronounced similarities in experiments and simulations. The opposite of spreading, i.e., evaporation of water droplets, leads to a characteristic receding motion first in the direction parallel to the stripes, while the contact line remains pinned perpendicular to the stripes. Only when the aspect ratio is close to unity, the contact line also starts to recede in the perpendicular direction. Very similar behavior was observed in the LBM simulations. Finally, droplet movement can be induced by a gradient in surface wettability. LBM simulations show good semiquantitative agreement with experimental results of decanol droplets on a well-defined striped gradient, which move from high- to low-contact angle surfaces. Similarities and differences for all systems are described and discussed in terms of the predictive capabilities of LBM simulations to model direction wetting.

  11. Numerical simulations of Hurricane Bertha using a mesoscale atmospheric model

    SciTech Connect

    Buckley, R.L.

    1996-08-01

    The Regional Atmospheric Model System (RAMS) has been used to simulate Hurricane Bertha as it moved toward and onto shore during the period July 10--12, 1996. Using large-scale atmospheric data from 00 UTC, 11 July (Wednesday evening) to initialize the model, a 36-hour simulation was created for a domain centered over the Atlantic Ocean east of the Florida coast near Jacksonville. The simulated onshore impact time of the hurricane was much earlier than observed (due to the use of results from the large-scale model, which predicted early arrival). However, the movement of the hurricane center (eye) as it approached the North Carolina/South Carolina coast as simulated in RAMS was quite good. Observations revealed a northerly storm track off the South Carolina coast as it moved toward land. As it approached landfall, Hurricane Bertha turned to the north-northeast, roughly paralleling the North Carolina coast before moving inland near Wilmington. Large-scale model forecasts were unable to detect this change in advance and predicted landfall near Myrtle Beach, South Carolina; RAMS, however, correctly predicted the parallel coastal movement. For future hurricane activity in the southeast, RAMS is being configured to run in an operational model using input from the large-scale pressure data in hopes of providing more information on predicted hurricane movement and landfall location.

  12. Sparse spectrum model for the turbulent phase simulations

    NASA Astrophysics Data System (ADS)

    Charnotskii, Mikhail

    2013-05-01

    Monte-Carlo simulation of phase front perturbations by atmospheric turbulence finds numerous applications for design and modeling of the adaptive optics systems, laser beams propagation simulations, and evaluating the performance of the various optical systems operating in the open air environment. Accurate generation of two-dimensional random fields of turbulent phase is complicated by the enormous diversity of scales that can reach five orders in magnitude in each coordinate. In addition there is a need for generation of the long "ribbons" of turbulent phase that are used to represent the time evolution of the wave front. This makes it unfeasible to use the standard discrete Fourier transform-based technique as a basis for the Monte-Carlo simulation algorithm. We propose a novel concept for turbulent phase - the Sparse Spectrum (SS) random field. The principle assumption of the SS model is that each realization of the random field has a discrete random spectral support. Statistics of the random amplitudes and wave vectors of the SS model are arranged to provide the required spectral and correlation properties of the random field. The SS-based Monte-Carlo model offers substantial reduction of computer costs for simulation of the wide-band random fields and processes, and is capable of generating long aperiodic phase "ribbons". We report the results of model trials that determine the number of sparse components, and the range of wavenumbers that is necessary to accurately reproduce the random field with a power-law spectrum.

  13. Gstat: a program for geostatistical modelling, prediction and simulation

    NASA Astrophysics Data System (ADS)

    Pebesma, Edzer J.; Wesseling, Cees G.

    1998-01-01

    Gstat is a computer program for variogram modelling, and geostatistical prediction and simulation. It provides a generic implementation of the multivariable linear model with trends modelled as a linear function of coordinate polynomials or of user-defined base functions, and independent or dependent, geostatistically modelled, residuals. Simulation in gstat comprises conditional or unconditional (multi-) Gaussian sequential simulation of point values or block averages, or (multi-) indicator sequential simulation. Besides many of the popular options found in other geostatistical software packages, gstat offers the unique combination of (i) an interactive user interface for modelling variograms and generalized covariances (residual variograms), that uses the device-independent plotting program gnuplot for graphical display, (ii) support for several ascii and binary data and map file formats for input and output, (iii) a concise, intuitive and flexible command language, (iv) user customization of program defaults, (v) no built-in limits, and (vi) free, portable ANSI-C source code. This paper describes the class of problems gstat can solve, and addresses aspects of efficiency and implementation, managing geostatistical projects, and relevant technical details.

  14. Numerical Simulation and Cold Modeling experiments on Centrifugal Casting

    NASA Astrophysics Data System (ADS)

    Keerthiprasad, Kestur Sadashivaiah; Murali, Mysore Seetharam; Mukunda, Pudukottah Gopaliengar; Majumdar, Sekhar

    2011-02-01

    In a centrifugal casting process, the fluid flow eventually determines the quality and characteristics of the final product. It is difficult to study the fluid behavior here because of the opaque nature of melt and mold. In the current investigation, numerical simulations of the flow field and visualization experiments on cold models have been carried out for a centrifugal casting system using horizontal molds and fluids of different viscosities to study the effect of different process variables on the flow pattern. The effects of the thickness of the cylindrical fluid annulus formed inside the mold and the effects of fluid viscosity, diameter, and rotational speed of the mold on the hollow fluid cylinder formation process have been investigated. The numerical simulation results are compared with corresponding data obtained from the cold modeling experiments. The influence of rotational speed in a real-life centrifugal casting system has also been studied using an aluminum-silicon alloy. Cylinders of different thicknesses are cast at different rotational speeds, and the flow patterns observed visually in the actual castings are found to be similar to those recorded in the corresponding cold modeling experiments. Reasonable agreement is observed between the results of numerical simulation and the results of cold modeling experiments with different fluids. The visualization study on the hollow cylinders produced in an actual centrifugal casting process also confirm the conclusions arrived at from the cold modeling experiments and numerical simulation in a qualitative sense.

  15. Simulations and Transport Models for Imbalanced Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Ng, Chung-Sang; Dennis, T.

    2016-10-01

    We present results from a series of three-dimensional simulations of magnetohydrodynamic (MHD) turbulence based on reduced MHD equations. Alfven waves are launched from both ends of a long tube along the background uniform magnetic field so that turbulence develops due to collision between counter propagating Alfven waves in the interior region. Waves are launched randomly with specified correlation time Tc such that the length of the tube, L, is greater than (but of the same order of) VA *Tc such that turbulence can fill most of the tube. While waves at both ends are launched with equal power, turbulence generated is imbalanced in general, with normalized cross-helicity gets close to -1 at one end and 1 at the other end. This simulation setup allows easier comparison of turbulence properties with one-dimensional turbulence transport models, which have been applied rather successfully in modeling solar wind turbulence. However, direct comparison of such models with full simulations of solar wind turbulence is difficult due to much higher level of complexity involved. We will present our latest simulations at different resolutions with decreasing dissipation (resistivity and viscosity) levels and compare with model outputs from turbulence transport models. This work is supported by a NASA Grant NNX15AU61G.

  16. Inviscid Wall-Modeled Large Eddy Simulations for Improved Efficiency

    NASA Astrophysics Data System (ADS)

    Aikens, Kurt; Craft, Kyle; Redman, Andrew

    2015-11-01

    The accuracy of an inviscid flow assumption for wall-modeled large eddy simulations (LES) is examined because of its ability to reduce simulation costs. This assumption is not generally applicable for wall-bounded flows due to the high velocity gradients found near walls. In wall-modeled LES, however, neither the viscous near-wall region or the viscous length scales in the outer flow are resolved. Therefore, the viscous terms in the Navier-Stokes equations have little impact on the resolved flowfield. Zero pressure gradient flat plate boundary layer results are presented for both viscous and inviscid simulations using a wall model developed previously. The results are very similar and compare favorably to those from another wall model methodology and experimental data. Furthermore, the inviscid assumption reduces simulation costs by about 25% and 39% for supersonic and subsonic flows, respectively. Future research directions are discussed as are preliminary efforts to extend the wall model to include the effects of unresolved wall roughness. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Computational resources on TACC Stampede were provided under XSEDE allocation ENG150001.

  17. THE Antarctic Atmospheric Energy Budget: Observations and Model Simulations

    NASA Astrophysics Data System (ADS)

    Previdi, M. J.; Smith, K. L.; Polvani, L. M.

    2014-12-01

    We present a new, observationally-based estimate of the atmospheric energy budget for the Antarctic polar cap (the region poleward of 70°S). This energy budget is constructed using state-of-the-art reanalysis products from ECMWF [the ECMWF Interim Re-Analysis (ERA-Interim)] and Clouds and the Earth's Radiant Energy System (CERES) top-of-atmosphere (TOA) radiative fluxes. We find that the climatological mean Antarctic energy budget is characterized by an approximate balance between the TOA net outgoing radiation and the horizontal convergence of atmospheric energy transport, with the net surface energy flux and atmospheric energy storage generally being small in comparison. We compare these observationally-based results with coupled atmosphere-ocean general circulation model simulations that have been made available as part of the Coupled Model Intercomparison Project, phase 5 (CMIP5). While CMIP5 models generally perform well in simulating the observed climatological mean energy budget, some notable model biases are apparent. These biases are most pronounced during the austral summer and fall seasons, with the largest biases (approaching 30 W m-2 for some models) occurring for the TOA net incoming shortwave radiation during summer. Finally, we examine the causes of model biases (e.g., deficiencies in the simulated cloud cover and sea ice), as well as their relationship to the simulated twenty-first century trends in the energy budget. We find a statistically significant inverse correlation across the CMIP5 models between the present-day biases in atmospheric energy transport into the polar cap, and the simulated future changes in energy transport over the twenty-first century. Possible reasons for this relationship are discussed.

  18. Simulations of Mineral Dust Content With CHIMERE-Dust Model

    NASA Astrophysics Data System (ADS)

    Schmechtig, C.; Marticorena, B.; Menut, L.; Bergametti, G.

    2006-12-01

    Simulations of the mineral dust cycle have been performed whith CHIMERE-Dust model over a domain that includes North Africa, the Mediterranean basin and the North Tropical Atlantic Ocean (10S-60N and 90W-90E) with a 1°x1° resolution using the ECMWF (European Center for Medium-Range Weather Forecasts) meteorological fields for two years, 2000 and 2001. As a validation, we compare the simulated dust concentration fields with photometric data from the AERONET network. From the comparisons between the simulated and measured aerosol optical depth for several stations of the Mediterranean basin, the model appears to reproduce correctly the intensity and occurrences of the dust events. Over Western Africa, the results are not as satisfying since some of the most intense dust events observed on the continent and downwind are not captured by the model. In addition, the simulated events are generally underestimated compared to the measured ones. It appears that these differences in the model performances are connected to the origin of the dust plumes. For example, dust plumes coming from Libya are well simulated while dust plumes originating from the Bodélé depression not as frequent as intense as the observations suggest. Soil properties in these two regions are comparable and typical of very erodible surfaces. We thus focused on the comparison between the ECMWF 10m wind speed fields and 10m wind speed measured at the meteorological stations located in both areas. We noticed that over Libya, the measured and ECMWF 10m wind speed are in very good agreement, while the meteorological model does not reproduce the extrema of the measured wind speed in the Bodélé depression. We found that a crude empirical correction of the 10m wind field in the Bodélé Depression significantly improve the simulations in terms of occurrence and of intensity.

  19. Current Water Deficit Stress Simulations in Selected Agricultural System Simulation Models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    System models, which adequately simulate plant water stress effects, are valuable tools for developing management practices with improved water use efficiency in agriculture. Plants experience water stress when its supply in the soil fails to meet the demand. Although it is easy to define the conc...

  20. Optimization Model for Web Based Multimodal Interactive Simulations.

    PubMed

    Halic, Tansel; Ahn, Woojin; De, Suvranu

    2015-07-15

    This paper presents a technique for optimizing the performance of web based multimodal interactive simulations. For such applications where visual quality and the performance of simulations directly influence user experience, overloading of hardware resources may result in unsatisfactory reduction in the quality of the simulation and user satisfaction. However, optimization of simulation performance on individual hardware platforms is not practical. Hence, we present a mixed integer programming model to optimize the performance of graphical rendering and simulation performance while satisfying application specific constraints. Our approach includes three distinct phases: identification, optimization and update. In the identification phase, the computing and rendering capabilities of the client device are evaluated using an exploratory proxy code. This data is utilized in conjunction with user specified design requirements in the optimization phase to ensure best possible computational resource allocation. The optimum solution is used for rendering (e.g. texture size, canvas resolution) and simulation parameters (e.g. simulation domain) in the update phase. Test results are presented on multiple hardware platforms with diverse computing and graphics capabilities to demonstrate the effectiveness of our approach.

  1. Optimization Model for Web Based Multimodal Interactive Simulations

    PubMed Central

    Halic, Tansel; Ahn, Woojin; De, Suvranu

    2015-01-01

    This paper presents a technique for optimizing the performance of web based multimodal interactive simulations. For such applications where visual quality and the performance of simulations directly influence user experience, overloading of hardware resources may result in unsatisfactory reduction in the quality of the simulation and user satisfaction. However, optimization of simulation performance on individual hardware platforms is not practical. Hence, we present a mixed integer programming model to optimize the performance of graphical rendering and simulation performance while satisfying application specific constraints. Our approach includes three distinct phases: identification, optimization and update. In the identification phase, the computing and rendering capabilities of the client device are evaluated using an exploratory proxy code. This data is utilized in conjunction with user specified design requirements in the optimization phase to ensure best possible computational resource allocation. The optimum solution is used for rendering (e.g. texture size, canvas resolution) and simulation parameters (e.g. simulation domain) in the update phase. Test results are presented on multiple hardware platforms with diverse computing and graphics capabilities to demonstrate the effectiveness of our approach. PMID:26085713

  2. Simulating tidal evolution and encounters with mass-spring models

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.; Frouard, Julien; Ebinger, Cynthia; Giannella, David; Efroimsky, Michael; Shaw, John

    2016-05-01

    We have recently found that we can directly simulate tidal spin down of viscoelastic objects using damped springs within an N-body code. But there is a 30% discrepancy between the torque analytically predicted and that numerically measured and we still have not identified the cause!Close tidal encounters among large planetesimals and moons were more common than impacts. Using a mass spring model within an N-body simulation, we simulate the deformation of the surface caused by a close tidal encounter and find tidal encounters can induce sufficient stress on the surface to cause brittle failure of an icy crust. Simulated fractures can extend a large fraction of the radius of body. Strong tidal encounters may be responsible for the formation of long graben complexes and chasmata in ancient terrain of icy moons such as Dione, Tethys, Ariel and Charon.

  3. Frameworks for Assessing the Quality of Modeling and Simulation Capabilities

    NASA Astrophysics Data System (ADS)

    Rider, W. J.

    2012-12-01

    The importance of assuring quality in modeling and simulation has spawned several frameworks for structuring the examination of quality. The format and content of these frameworks provides an emphasis, completeness and flow to assessment activities. I will examine four frameworks that have been developed and describe how they can be improved and applied to a broader set of high consequence applications. Perhaps the first of these frameworks was known as CSAU [Boyack] (code scaling, applicability and uncertainty) used for nuclear reactor safety and endorsed the United States' Nuclear Regulatory Commission (USNRC). This framework was shaped by nuclear safety practice, and the practical structure needed after the Three Mile Island accident. It incorporated the dominant experimental program, the dominant analysis approach, and concerns about the quality of modeling. The USNRC gave it the force of law that made the nuclear industry take it seriously. After the cessation of nuclear weapons' testing the United States began a program of examining the reliability of these weapons without testing. This program utilizes science including theory, modeling, simulation and experimentation to replace the underground testing. The emphasis on modeling and simulation necessitated attention on the quality of these simulations. Sandia developed the PCMM (predictive capability maturity model) to structure this attention [Oberkampf]. PCMM divides simulation into six core activities to be examined and graded relative to the needs of the modeling activity. NASA [NASA] has built yet another framework in response to the tragedy of the space shuttle accidents. Finally, Ben-Haim and Hemez focus upon modeling robustness and predictive fidelity in another approach. These frameworks are similar, and applied in a similar fashion. The adoption of these frameworks at Sandia and NASA has been slow and arduous because the force of law has not assisted acceptance. All existing frameworks are

  4. On the simulation of nonlinear bidimensional spiking neuron models.

    PubMed

    Touboul, Jonathan

    2011-07-01

    Bidimensional spiking models are garnering a lot of attention for their simplicity and their ability to reproduce various spiking patterns of cortical neurons and are used particularly for large network simulations. These models describe the dynamics of the membrane potential by a nonlinear differential equation that blows up in finite time, coupled to a second equation for adaptation. Spikes are emitted when the membrane potential blows up or reaches a cutoff θ. The precise simulation of the spike times and of the adaptation variable is critical, for it governs the spike pattern produced and is hard to compute accurately because of the exploding nature of the system at the spike times. We thoroughly study the precision of fixed time-step integration schemes for this type of model and demonstrate that these methods produce systematic errors that are unbounded, as the cutoff value is increased, in the evaluation of the two crucial quantities: the spike time and the value of the adaptation variable at this time. Precise evaluation of these quantities therefore involves very small time steps and long simulation times. In order to achieve a fixed absolute precision in a reasonable computational time, we propose here a new algorithm to simulate these systems based on a variable integration step method that either integrates the original ordinary differential equation or the equation of the orbits in the phase plane, and compare this algorithm with fixed time-step Euler scheme and other more accurate simulation algorithms.

  5. Technology evaluation, assessment, modeling, and simulation: the TEAMS capability

    NASA Astrophysics Data System (ADS)

    Holland, Orgal T.; Stiegler, Robert L.

    1998-08-01

    The United States Marine Corps' Technology Evaluation, Assessment, Modeling and Simulation (TEAMS) capability, located at the Naval Surface Warfare Center in Dahlgren Virginia, provides an environment for detailed test, evaluation, and assessment of live and simulated sensor and sensor-to-shooter systems for the joint warfare community. Frequent use of modeling and simulation allows for cost effective testing, bench-marking, and evaluation of various levels of sensors and sensor-to-shooter engagements. Interconnectivity to live, instrumented equipment operating in real battle space environments and to remote modeling and simulation facilities participating in advanced distributed simulations (ADS) exercises is available to support a wide- range of situational assessment requirements. TEAMS provides a valuable resource for a variety of users. Engineers, analysts, and other technology developers can use TEAMS to evaluate, assess and analyze tactical relevant phenomenological data on tactical situations. Expeditionary warfare and USMC concept developers can use the facility to support and execute advanced warfighting experiments (AWE) to better assess operational maneuver from the sea (OMFTS) concepts, doctrines, and technology developments. Developers can use the facility to support sensor system hardware, software and algorithm development as well as combat development, acquisition, and engineering processes. Test and evaluation specialists can use the facility to plan, assess, and augment their processes. This paper presents an overview of the TEAMS capability and focuses specifically on the technical challenges associated with the integration of live sensor hardware into a synthetic environment and how those challenges are being met. Existing sensors, recent experiments and facility specifications are featured.

  6. High Resolution Modeling of Tropical Cyclones Using Rare Event Simulation

    NASA Astrophysics Data System (ADS)

    Plotkin, D. A.; Abbot, D. S.; Weare, J.

    2014-12-01

    Tropical cyclones (TCs) present a challenge to modeling using general circulation models (GCMs) because they involve processes and structures that are too fine for GCMs to resolve. TCs have fine structures - e.g. the eye, eyewall, and rain bands - with length scales on the order of 10 km, while GCMs have typical resolutions on the order of 50-100 km. High resolution GCM runs that are sufficiently long to exhibit multiple TCs can be prohibitively computationally expensive. Thus, while GCMs exhibit TC-like vortices with similar spatial and temporal frequencies to observed TCs, the ability of GCMs to reproduce fine TC structures remains largely untested. In this study, we use recently developed rare event analysis and simulation methods to selectively simulate TCs under GCMs at very high resolution. These rare event simulation methods have been developed mostly in the context of computational chemistry, but are broadly applicable. They allow (either by careful manipulation of the model or by selection of trajectories) direct and detailed interrogation of the event of interest without introducing error and without the need to simulated for long periods of time to see the event. By creating targeted, high resolution GCM simulations with many TCs, we hope to determine whether or not GCMs can capture fine TC structures such as eyewalls and individual rain bands.

  7. NEAMS FPL M2 Milestone Report: Development of a UO₂ Grain Size Model using Multicale Modeling and Simulation

    SciTech Connect

    Tonks, Michael R; Zhang, Yongfeng; Bai, Xianming

    2014-06-01

    This report summarizes development work funded by the Nuclear Energy Advanced Modeling Simulation program's Fuels Product Line (FPL) to develop a mechanistic model for the average grain size in UO₂ fuel. The model is developed using a multiscale modeling and simulation approach involving atomistic simulations, as well as mesoscale simulations using INL's MARMOT code.

  8. Integrated Water Resources Simulation Model for Rural Community

    NASA Astrophysics Data System (ADS)

    Li, Y.-H.; Liao, W.-T.; Tung, C.-P.

    2012-04-01

    The purpose of this study is to develop several water resources simulation models for residence houses, constructed wetlands and farms and then integrate these models for a rural community. Domestic and irrigation water uses are the major water demand in rural community. To build up a model estimating domestic water demand for residence houses, the average water use per person per day should be accounted first, including water uses of kitchen, bathroom, toilet and laundry. On the other hand, rice is the major crop in the study region, and its productive efficiency sometimes depends on the quantity of irrigation water. The water demand can be estimated by crop water use, field leakage and water distribution loss. Irrigation water comes from rainfall, water supply system and reclaimed water which treated by constructed wetland. In recent years, constructed wetlands play an important role in water resources recycle. They can purify domestic wastewater for water recycling and reuse. After treating from constructed wetlands, the reclaimed water can be reused in washing toilets, watering gardens and irrigating farms. Constructed wetland is one of highly economic benefits for treating wastewater through imitating the processing mechanism of natural wetlands. In general, the treatment efficiency of constructed wetlands is determined by evapotranspiration, inflow, and water temperature. This study uses system dynamics modeling to develop models for different water resource components in a rural community. Furthermore, these models are integrated into a whole system. The model not only is utilized to simulate how water moves through different components, including residence houses, constructed wetlands and farms, but also evaluates the efficiency of water use. By analyzing the flow of water, the water resource simulation model can optimizes water resource distribution under different scenarios, and the result can provide suggestions for designing water resource system of a

  9. 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.

  10. Mean Line Pump Flow Model in Rocket Engine System Simulation

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.; Lavelle, Thomas M.

    2000-01-01

    A mean line pump flow modeling method has been developed to provide a fast capability for modeling turbopumps of rocket engines. Based on this method, a mean line pump flow code PUMPA has been written that can predict the performance of pumps at off-design operating conditions, given the loss of the diffusion system at the design point. The pump code can model axial flow inducers, mixed-flow and centrifugal pumps. The code can model multistage pumps in series. The code features rapid input setup and computer run time, and is an effective analysis and conceptual design tool. The map generation capability of the code provides the map information needed for interfacing with a rocket engine system modeling code. The off-design and multistage modeling capabilities of the code permit parametric design space exploration of candidate pump configurations and provide pump performance data for engine system evaluation. The PUMPA code has been integrated with the Numerical Propulsion System Simulation (NPSS) code and an expander rocket engine system has been simulated. The mean line pump flow code runs as an integral part of the NPSS rocket engine system simulation and provides key pump performance information directly to the system model at all operating conditions.

  11. Protein adsorption on nanoparticles: model development using computer simulation

    NASA Astrophysics Data System (ADS)

    Shao, Qing; Hall, Carol K.

    2016-10-01

    The adsorption of proteins on nanoparticles results in the formation of the protein corona, the composition of which determines how nanoparticles influence their biological surroundings. We seek to better understand corona formation by developing models that describe protein adsorption on nanoparticles using computer simulation results as data. Using a coarse-grained protein model, discontinuous molecular dynamics simulations are conducted to investigate the adsorption of two small proteins (Trp-cage and WW domain) on a model nanoparticle of diameter 10.0 nm at protein concentrations ranging from 0.5 to 5 mM. The resulting adsorption isotherms are well described by the Langmuir, Freundlich, Temkin and Kiselev models, but not by the Elovich, Fowler-Guggenheim and Hill-de Boer models. We also try to develop a generalized model that can describe protein adsorption equilibrium on nanoparticles of different diameters in terms of dimensionless size parameters. The simulation results for three proteins (Trp-cage, WW domain, and GB3) on four nanoparticles (diameter  =  5.0, 10.0, 15.0, and 20.0 nm) illustrate both the promise and the challenge associated with developing generalized models of protein adsorption on nanoparticles.

  12. A holistic water depth simulation model for small ponds

    NASA Astrophysics Data System (ADS)

    Ali, Shakir; Ghosh, Narayan C.; Mishra, P. K.; Singh, R. K.

    2015-10-01

    Estimation of time varying water depth and time to empty of a pond is prerequisite for comprehensive and coordinated planning of water resource for its effective utilization. A holistic water depth simulation (HWDS) and time to empty (TE) model for small, shallow ephemeral ponds have been derived by employing the generalized model based on the Green-Ampt equation in the basic water balance equation. The HWDS model includes time varying rainfall, runoff, surface water evaporation, outflow and advancement of wetting front length as external inputs. The TE model includes two external inputs; surface water evaporation and advancement of wetting front length. Both the models also consider saturated hydraulic conductivity and fillable porosity of the pond's bed material as their parameters. The solution of the HWDS model involved numerical iteration in successive time intervals. The HWDS model has successfully evaluated with 3 years of field data from two small ponds located within a watershed in a semi-arid region in western India. The HWDS model simulated time varying water depth in the ponds with high accuracy as shown by correlation coefficient (R2 ⩾ 0.9765), index of agreement (d ⩾ 0.9878), root mean square errors (RMSE ⩽ 0.20 m) and percent bias (PB ⩽ 6.23%) for the pooled data sets of the measured and simulated water depth. The statistical F and t-tests also confirmed the reliability of the HWDS model at probability level, p ⩽ 0.0001. The response of the TE model showed its ability to estimate the time to empty the ponds. An additional field calibration and validation of the HWDS and TE models with observed field data in varied hydro-climatic conditions could be conducted to increase the applicability and credibility of the models.

  13. Rating global magnetosphere model simulations through statistical data-model comparisons

    NASA Astrophysics Data System (ADS)

    Ridley, A. J.; De Zeeuw, D. L.; Rastätter, L.

    2016-10-01

    The Community Coordinated Modeling Center (CCMC) was created in 2000 to allow researchers to remotely run simulations and explore the results through online tools. Since that time, over 10,000 simulations have been conducted at CCMC through their runs-on-request service. Many of those simulations have been event studies using global magnetohydrodynamic (MHD) models of the magnetosphere. All of these simulations are available to the general public to explore and utilize. Many of these simulations have had virtual satellites flown through the model to extract the simulation results at the satellite location as a function of time. This study used 662 of these magnetospheric simulations, with a total of 2503 satellite traces, to statistically compare the magnetic field simulated by models to the satellite data. Ratings for each satellite trace were created by comparing the root-mean-square error of the trace with all of the other traces for the given satellite and magnetic field component. The 1-5 ratings, with 5 being the best quality run, are termed "stars." From these star ratings, a few conclusions were made: (1) Simulations tend to have a lower rating for higher levels of activity; (2) there was a clear bias in the Bz component of the simulations at geosynchronous orbit, implying that the models were challenged in simulating the inner magnetospheric dynamics correctly; and (3) the highest performing model included a coupled ring current model, which was about 0.15 stars better on average than the same model without the ring current model coupling.

  14. Modelling and simulation in the pharmaceutical industry--some reflections.

    PubMed

    Burman, Carl-Fredrik; Wiklund, Stig Johan

    2011-01-01

    Modelling and simulation (M&S) is increasingly being applied in (clinical) drug development. It provides an opportune area for the community of pharmaceutical statisticians to pursue. In this article, we highlight useful principles behind the application of M&S. We claim that M&S should be focussed on decisions, tailored to its purpose and based in applied sciences, not relying entirely on data-driven statistical analysis. Further, M&S should be a continuous process making use of diverse information sources and applying Bayesian and frequentist methodology, as appropriate. In addition to forming a basis for analysing decision options, M&S provides a framework that can facilitate communication between stakeholders. Besides the discussion on modelling philosophy, we also describe how standard simulation practice can be ineffective and how simulation efficiency can often be greatly improved.

  15. Performance potential for simulating spin models on GPU

    NASA Astrophysics Data System (ADS)

    Weigel, Martin

    2012-04-01

    Graphics processing units (GPUs) are recently being used to an increasing degree for general computational purposes. This development is motivated by their theoretical peak performance, which significantly exceeds that of broadly available CPUs. For practical purposes, however, it is far from clear how much of this theoretical performance can be realized in actual scientific applications. As is discussed here for the case of studying classical spin models of statistical mechanics by Monte Carlo simulations, only an explicit tailoring of the involved algorithms to the specific architecture under consideration allows to harvest the computational power of GPU systems. A number of examples, ranging from Metropolis simulations of ferromagnetic Ising models, over continuous Heisenberg and disordered spin-glass systems to parallel-tempering simulations are discussed. Significant speed-ups by factors of up to 1000 compared to serial CPU code as well as previous GPU implementations are observed.

  16. Modeling and Simulation for Mission Operations Work System Design

    NASA Technical Reports Server (NTRS)

    Sierhuis, Maarten; Clancey, William J.; Seah, Chin; Trimble, Jay P.; Sims, Michael H.

    2003-01-01

    Work System analysis and design is complex and non-deterministic. In this paper we describe Brahms, a multiagent modeling and simulation environment for designing complex interactions in human-machine systems. Brahms was originally conceived as a business process design tool that simulates work practices, including social systems of work. We describe our modeling and simulation method for mission operations work systems design, based on a research case study in which we used Brahms to design mission operations for a proposed discovery mission to the Moon. We then describe the results of an actual method application project-the Brahms Mars Exploration Rover. Space mission operations are similar to operations of traditional organizations; we show that the application of Brahms for space mission operations design is relevant and transferable to other types of business processes in organizations.

  17. Soft tissue modelling through autowaves for surgery simulation.

    PubMed

    Zhong, Yongmin; Shirinzadeh, Bijan; Alici, Gursel; Smith, Julian

    2006-09-01

    Modelling of soft tissue deformation is of great importance to virtual reality based surgery simulation. This paper presents a new methodology for simulation of soft tissue deformation by drawing an analogy between autowaves and soft tissue deformation. The potential energy stored in a soft tissue as a result of a deformation caused by an external force is propagated among mass points of the soft tissue by non-linear autowaves. The novelty of the methodology is that (i) autowave techniques are established to describe the potential energy distribution of a deformation for extrapolating internal forces, and (ii) non-linear materials are modelled with non-linear autowaves other than geometric non-linearity. Integration with a haptic device has been achieved to simulate soft tissue deformation with force feedback. The proposed methodology not only deals with large-range deformations, but also accommodates isotropic, anisotropic and inhomogeneous materials by simply changing diffusion coefficients.

  18. Safety simulation model for drivers of adapted cars

    NASA Astrophysics Data System (ADS)

    Eixerés, B.; Masiá, J.; Dols, J. F.; Colomina, F. J.

    2009-11-01

    In cases where frontal impacts take place in vehicles in which control devices have been mounted, driver safety is compromised by the effect of these devices on the correct working of the driver airbag [1]. The simulation provided information on the forces involved in the injuries sustained by the driver. In this simulation, the crash survival space is based on a frontal impact. On one hand, there is a passive set of forces generated by the steering control device and the steering wheel. On the other hand, there are the forces generated by the airbag. An airbag model was used, formed by a fabric bag which is correctly folded, and filled with a gas that expands according to a theoretical model. In this simulation, a dummy is also added to represent the driver, who is correctly secured with the safety belt. These elements are subjected to decelerations corresponding to a frontal impact. This work analyzes what happens during these impacts.

  19. Simulation of an epidemic model with vector transmission

    NASA Astrophysics Data System (ADS)

    Dickman, Adriana G.; Dickman, Ronald

    2015-03-01

    We study a lattice model for vector-mediated transmission of a disease in a population consisting of two species, A and B, which contract the disease from one another. Individuals of species A are sedentary, while those of species B (the vector) diffuse in space. Examples of such diseases are malaria, dengue fever, and Pierce's disease in vineyards. The model exhibits a phase transition between an absorbing (infection free) phase and an active one as parameters such as infection rates and vector density are varied. We study the static and dynamic critical behavior of the model using initial spreading, initial decay, and quasistationary simulations. Simulations are checked against mean-field analysis. Although phase transitions to an absorbing state fall generically in the directed percolation universality class, this appears not to be the case for the present model.

  20. Applying simulation and logistics modeling to tansportation issues

    SciTech Connect

    Funkhouser, B.R.; Ballweg, E.L.; Mackoy, R.D.

    1995-08-15

    This paper describes an application where transportation logistics and simulation tools are integrated to create a modeling environment for transportation planning. The Transportation Planning Model (TPM) is a tool developed for the Department of Energy (DOE) to aid in the long-term planning of their transportation resources. The focus of the tool is to aid DOE and Sandia National Laboratory analysts in the planning of future fleet sizes, driver and support personnel sizes, base site locations, and resource balancing among the base sites. The design approach is to develop a rapid modeling environment which integrates graphical user interfaces, logistics optimizing tools, and simulation modeling. Using the TPM an analyst can easily set up a shipment scenario and perform multiple ``What If`` evaluations. The TPM has been developed on personal computers using commercial off-the-shelf software tools under the WINDOW{reg_sign} operating environment.