4,793 Matching Results

Search Results

Advanced search parameters have been applied.

Simulating relativistic beam and plasma systems using an optimal boosted frame

Description: It was shown recently that it may be computationally advantageous to perform computer simulations in a Lorentz boosted frame for a certain class of systems. However, even if the computer model relies on a covariant set of equations, it was pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup. In this paper, we summarize the findings, the difficulties and their solutions, and review the applications of the technique that have been performed to date.
Date: May 1, 2009
Creator: Vay, J.-L.; Bruhwiler, D. L.; Geddes, C. G. R.; Fawley, W. M.; Martins, S. F.; Cary, J. R. et al.
Partner: UNT Libraries Government Documents Department

Computer-Assisted Discovery and Proof

Description: With the advent of powerful, widely-available mathematical software, combined with ever-faster computer hardware, we are approaching a day when both the discovery and proof of mathematical facts can be done in a computer-assisted manner. his article presents several specific examples of this new paradigm in action.
Date: December 10, 2007
Creator: Bailey, David H. & Borwein, Jonathan M.
Partner: UNT Libraries Government Documents Department

Using EnergyPlus for California Title-24 compliancecalculations

Description: For the past decade, the non-residential portion of California's Title-24 building energy standard has relied on DOE-2.1E as the reference computer simulation program for development as well as compliance. However, starting in 2004, the California Energy Commission has been evaluating the possible use of Energy Plus as the reference program in future revisions of Title-24. As part of this evaluation, the authors converted the Alternate Compliance Method (ACM) certification test suite of 150 DOE-2 files to Energy Plus, and made parallel DOE-2 and Energy Plus runs for this extensive set of test cases. A customized version of DOE-2.1E named doe2ep was developed to automate the conversion process. This paper describes this conversion process, including the difficulties in establishing an apples-to-apples comparison between the two programs, and summarizes how the DOE-2 and Energy Plus results compare for the ACM test cases.
Date: August 26, 2006
Creator: Huang, Joe; Bourassa, Norman; Buhl, Fred; Erdem, Ender & Hitchcock, Rob
Partner: UNT Libraries Government Documents Department

Manifold methods for methane combustion

Description: Objective is to develop a new method for studying realistic chemistry in turbulent methane combustion with NO{sub x} mechanism. The realistic chemistry is a simplification to a more detailed chemistry based on the manifold method; accuracy is determined by interaction between the transport process and the chemical reaction. In this new (tree) method, probability density function or partially stirred reactor calculations are performed. Compared with the reduced mechanism, manifold, and tabulation methods, the new method overcomes drawbacks of the reduced mechanism method and preserves the advantages of the manifold method. Accuracy is achieved by specifying the size of the cell.
Date: December 31, 1995
Creator: Yang, B. & Pope, S.B.
Partner: UNT Libraries Government Documents Department

Development of an advanced system identification technique for comparing ADAMS analytical results with modal test data for a MICON 65/13 wind turbine

Description: This work uses the theory developed in NREL/TP--442-7110 to analyze simulated data from an ADAMS (Automated Dynamic Analysis of Mechanical Systems) model of the MICON 65/13 wind turbine. The Observer/Kalman Filter identification approach is expanded to use input-output time histories from ADAMS simulations or structural test data. A step by step outline is offered on how the tools developed in this research, can be used for validation of the ADAMS model.
Date: July 1, 1995
Creator: Bialasiewicz, J.T.
Partner: UNT Libraries Government Documents Department

Computational Biology, Advanced Scientific Computing, and Emerging Computational Architectures

Description: This CRADA was established at the start of FY02 with $200 K from IBM and matching funds from DOE to support post-doctoral fellows in collaborative research between International Business Machines and Oak Ridge National Laboratory to explore effective use of emerging petascale computational architectures for the solution of computational biology problems. 'No cost' extensions of the CRADA were negotiated with IBM for FY03 and FY04.
Date: June 27, 2007
Partner: UNT Libraries Government Documents Department

Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

Description: The combined effect of impedance and higher order chromaticity can act on the beam in a nontrivial manner which can cause a tune shift which depends on the relative momenta with respect to the 'on momentum' particle ({Delta}p/p). Experimentally, this tune shift affects the measurement of the linear chromaticity which is traditionally measured with a change of {Delta}p/p. The theory behind this effect will be derived in this paper. Computer simulations and experimental data from the Tevatron will be used to support the theory.
Date: August 1, 2011
Creator: Ranjbar, V.H.; /Tech-X, Boulder; Tan, C.Y. & /Fermilab
Partner: UNT Libraries Government Documents Department

IMPACT simulation and the SNS linac beam

Description: Multi-particle tracking simulations for the SNS linac beam dynamics studies are performed with the IMPACT code. Beam measurement results are compared with the computer simulations, including beam longitudinal halo and beam losses in the superconducting linac, transverse beam Courant-Snyder parameters and the longitudinal beam emittance in the linac. In most cases, the simulations show good agreement with the measured results.
Date: September 3, 2008
Creator: Zhang, Y. & Qiang, J.
Partner: UNT Libraries Government Documents Department

Developing close combat behaviors for simulated soldiers using genetic programming techniques.

Description: Genetic programming is a powerful methodology for automatically producing solutions to problems in a variety of domains. It has been used successfully to develop behaviors for RoboCup soccer players and simple combat agents. We will attempt to use genetic programming to solve a problem in the domain of strategic combat, keeping in mind the end goal of developing sophisticated behaviors for compound defense and infiltration. The simplified problem at hand is that of two armed agents in a small room, containing obstacles, fighting against each other for survival. The base case and three changes are considered: a memory of positions using stacks, context-dependent genetic programming, and strongly typed genetic programming. Our work demonstrates slight improvements from the first two techniques, and no significant improvement from the last.
Date: October 1, 2003
Creator: Pryor, Richard J. & Schaller, Mark J.
Partner: UNT Libraries Government Documents Department

Molecular Dynamics Simulations of Spinodal-Assisted Polymer Crystallization

Description: Large scale molecular dynamics simulations of bulk melts of polar (poly(vinylidene fluoride) (pVDF)) polymers are utilized to study chain conformation and ordering prior to crystallization under cooling. While the late stages of polymer crystallization have been studied in great detail, recent theoretical and experimental evidence indicates that there are important phenomena occurring in the early stages of polymer crystallization that are not understood to the same degree. When the polymer melt is quenched from a temperature above the melting temperature to the crystallization temperature, crystallization does not occur instantaneously. This initial interval without crystalline order is characterized as an induction period. It has been thought of as a nucleation period in the classical theories of polymer crystallization, but recent experiments, computer simulations, and theoretical work suggest that the initial period in polymer crystallization is assisted by a spinodal decomposition type mechanism. In this study we have achieved physically realistic length scales to study early stages of polymer ordering, and show that spinodal-assisted ordering prior to crystallization is operative in polar polymers suggesting general applicability of this process.
Date: July 8, 2005
Creator: Gee, R H; Lacevic, N M & Fried, L
Partner: UNT Libraries Government Documents Department

Atmospheric Data Package for the Composite Analysis

Description: The purpose of this data package is to summarize our conceptual understanding of atmospheric transport and deposition, describe how this understanding will be simplified for numerical simulation as part of the Composite Analysis (i.e., implementation model), and finally to provide the input parameters needed for the simulations.
Date: September 1, 2005
Creator: Napier, Bruce A. & Ramsdell, James V.
Partner: UNT Libraries Government Documents Department

Experimental and theoretical study of the residual product nuclide yields in thin targets irradiated with 100-2600 MeV protons.

Description: The work is aimed at measurements and computer simulations of independent and cumulative yields of residual product nuclei in thin targets relevant as target materials and structure materials for hybrid accelerator-driven systems coupled to high-energy proton accelerators.
Date: January 1, 2001
Creator: Titarenko, Y. E. (Yury E.); Batyaev, V. F. (Vyacheslav F.); Karpikhin, E. I. (Evgeny I.); Zhivun, V. M. (Valery M.); Koldobsky, A. B. (Aleksander B.); Mulambetov, R. D. (Ruslan D.) et al.
Partner: UNT Libraries Government Documents Department

Tracking Non-rigid Structures in Computer Simulations

Description: A key challenge in tracking moving objects is the correspondence problem, that is, the correct propagation of object labels from one time step to another. This is especially true when the objects are non-rigid structures, changing shape, and merging and splitting over time. In this work, we describe a general approach to tracking thousands of non-rigid structures in an image sequence. We show how we can minimize memory requirements and generate accurate results while working with only two frames of the sequence at a time. We demonstrate our results using data from computer simulations of a fluimix problem.
Date: January 10, 2008
Creator: Gezahegne, A & Kamath, C
Partner: UNT Libraries Government Documents Department

CFD analysis of laminar oscillating flows

Description: This paper describes a numerical simulations of oscillating flow in a constricted duct and compares the results with experimental and theoretical data. The numerical simulations were performed using the computational fluid dynamics (CFD) code CFX4.2. The numerical model simulates an experimental oscillating flow facility that was designed to test the properties and characteristics of oscillating flow in tapered ducts, also known as jet pumps. Jet pumps are useful devices in thermoacoustic machinery because they produce a secondary pressure that can counteract an unwanted effect called streaming, and significantly enhance engine efficiency. The simulations revealed that CFX could accurately model velocity, shear stress and pressure variations in laminar oscillating flow. The numerical results were compared to experimental data and theoretical predictions with varying success. The least accurate numerical results were obtained when laminar flow approached transition to turbulent flow.
Date: January 1, 2001
Creator: Booten, C. W. Charles W.); Konecni, S. (Snezana); Smith, B. L. (Barton L.) & Martin, R. A. (Richard A.)
Partner: UNT Libraries Government Documents Department

Distributed sensor networks with collective computation

Description: Simulations of a network of N sensors have been performed. The simulation space contains a number of sound sources and a large number of sensors. Each sensor is equipped with an omni-directional microphone and is capable of measuring only the time of arrival of a signal. Sensors are able to wirelessly transmit and receive packets of information, and have some computing power. The sensors were programmed to merge all information (received packets as well as local measurements) into a 'world view' for that node. This world view is then transmitted. In this way, information can slowly diffuse across the network. One node was monitored in the network as a proxy for when information had diffused across the network. Simulations demonstrated that the energy expended per sensor per time step was approximately independent of N.
Date: January 1, 2001
Creator: Lanman, D. R. (Douglas R.)
Partner: UNT Libraries Government Documents Department

Investigations of the Dynamics of Space Charged Dominated Beams

Description: We propose to perform investigations of the dynamics of space charge dominated beams. These investigations will support present activities such as the electron ring project at the University of Maryland as well as provide an improved basis for future accelerator designs. Computer simulations will provide the primary research element with improved code development being an integral part of the activities during the first period. We believe that one of the code development projects provides a unique strategy for the inclusion of longitudinal dynamics, and that this concept should provide a computationally rapid research tool.
Date: August 1, 2002
Creator: York, Richard C.
Partner: UNT Libraries Government Documents Department

Review of Understanding the Micro to Macro Behaviour of Rock FluidSystems

Description: The book consists of a series of summaries of studies supported by the Natural Environmental Research Council's thematic program of the same name. The objective of this research initiative was to improve understanding and characterization of subsurface fluid flow over a wide range of spatial scales through field investigations, laboratory studies, and computer simulations of these processes.
Date: January 22, 2007
Creator: Cortis, A.; Dobson, P.F. & Liu, H.H.
Partner: UNT Libraries Government Documents Department

Hydra: a service oriented architecture for scientific simulation integration

Description: One of the current major challenges in scientific modeling and simulation, in particular in the infrastructure-analysis community, is the development of techniques for efficiently and automatically coupling disparate tools that exist in separate locations on different platforms, implemented in a variety of languages and designed to be standalone. Recent advances in web-based platforms for integrating systems such as SOA provide an opportunity to address these challenges in a systematic fashion. This paper describes Hydra, an integrating architecture for infrastructure modeling and simulation that defines geography-based schemas that, when used to wrap existing tools as web services, allow for seamless plug-and-play composability. Existing users of these tools can enhance the value of their analysis by assessing how the simulations of one tool impact the behavior of another tool and can automate existing ad hoc processes and work flows for integrating tools together.
Date: January 1, 2008
Creator: Bent, Russell; Djidjev, Tatiana; Hayes, Birch P; Holland, Joe V; Khalsa, Hari S; Linger, Steve P et al.
Partner: UNT Libraries Government Documents Department

Speeding Up Simulations of Relativistic Systems using an Optimal Boosted Frame

Description: It can be computationally advantageous to perform computer simulations in a Lorentz boosted frame for a certain class of systems. However, even if the computer model relies on a covariant set of equations, it has been pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup. We summarize the findings, the difficulties and their solutions, and show that the technique enables simulations important to several areas of accelerator physics that are otherwise problematic, including self-consistent modeling in three-dimensions of laser wokefield accelerator stages at energies of 10 GeV and above.
Date: January 27, 2009
Creator: Vay, J.-L.; Fawley, W.M.; Geddes, C.G.R.; Cormier-Michel, E. & Grote, D.P.
Partner: UNT Libraries Government Documents Department

Optimal dynamic performance for high-precision actuators/stages.

Description: System dynamic performance of actuator/stage groups, such as those found in optical instrument positioning systems and other high-precision applications, is dependent upon both individual component behavior and the system configuration. Experimental modal analysis techniques were implemented to determine the six degree of freedom stiffnesses and damping for individual actuator components. These experimental data were then used in a multibody dynamic computer model to investigate the effect of stage group configuration. Running the computer model through the possible stage configurations and observing the predicted vibratory response determined the optimal stage group configuration. Configuration optimization can be performed for any group of stages, provided there is stiffness and damping data available for the constituent pieces.
Date: July 3, 2002
Creator: Preissner, C.; Lee, S.-H.; Royston, T. J. & Shu, D.
Partner: UNT Libraries Government Documents Department

ALE advantage in hypervelocity impact calculations

Description: The ALE3D code is used to model experiments relevant to hypervelocity impact lethality, carried out in the 4-5 km/s velocity range. The code is run in the Eulerian and ALE modes. Zoning in the calculations is refined beyond the level found in most lethality calculations, but still short of convergence. The level of zoning refinement that produces equivalent results in uniformly zoned Eulerian calculations and ALE ones utilizing specialized zoning, weighting and relaxation techniques is established. It takes 11 times fewer zones and about 60% as many cycles when ALE capabilities are used. Calculations are compared to experimental results.
Date: October 1, 1998
Creator: Gerassimenko, M. & Rathkopf, J.
Partner: UNT Libraries Government Documents Department

Process Simulation as Applied to Transuranic Waste Management

Description: The National Transuranic Waste System Model (the Model) is a computer simulation designed to evaluate the preparation and flow of TRU waste from generator sites throughout the Department of Energy (the Department) complex to the Waste Isolation Pilot Plant (WIPP) facility for disposal. The Model uses process simulation software to predict waste outputs of waste management operations as a function of time over the life of the WIPP. Process simulation modeling is a tool used by many industries, both private and public, to evaluate complex systems. For example a manufacturing plant might use process simulation to determine the possible effects of increasing the rate of production: will there be adequate resources (labor pool, raw goods, transportation capability); can the new production rate be sustained for an indefinite period of time without adding additional infrastructure. Process simulation modeling is also used by various military branches to ensure adequate supplies are delivered in a timely manner. The Department currently uses this technique as the basis for its National TRU Waste Management Plan Rev. 1 (DOE, 1997).
Date: January 1, 1999
Creator: Brown, M.; Downes, S. & Trone, J.
Partner: UNT Libraries Government Documents Department