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Diagnostics for the Combustion Science Workbench

Description: As the cost of computers declines relative to outfitting andmaintaining laser spectroscopy laboratories, computers will account foran increasing proportion of the research conducted in fundamentalcombustion science. W.C. Gardiner foresaw that progress will be limitedby the ability to understand the implications of what has been computedand to draw inferences about the elementary components of the combustionmodels. Yet the diagnostics that are routinely applied to computerexperiments have changed little from the sensitivity analyses includedwith the original chemkin software distribution. This paper describessome diagnostics capabilities that may be found on the virtual combustionscience workbench of the future. These diagnostics are illustrated bysome new results concerning which of the hydrogen/oxygen chain branchingreactions actually occur in flames, the increased formation of NOx inwrinkled flames versus flat flames, and the adequacy oftheoreticalpredictions of the effects of stretch. Several areas are identified wherework is needed, including the areas of combustion chemistry and laserdiagnostics, to make the virtual laboratory a reality.
Date: February 21, 2007
Creator: Grcar, J.F.; Day, M.S. & Bell, J.B.
Partner: UNT Libraries Government Documents Department

Analog Simulation of the Hanford N-Reactor Plant, Part 1: Description of the Overall Simulation Model

Description: Report that describes Hanford Laboratories' overall N-Reactor plant simulation model and its use to study the characteristics of the plant, plant operational procedures, and the effects of plant, operator, and control system malfunctions.
Date: September 1, 1964
Creator: Swanson, C. D.; Coughren, K. D.; Dionne, P. J. & Thieme, G. G.
Partner: UNT Libraries Government Documents Department

Modeling Complex Forest Ecology in a Parallel Computing Infrastructure

Description: Effective stewardship of forest ecosystems make it imperative to measure, monitor, and predict the dynamic changes of forest ecology. Measuring and monitoring provides us a picture of a forest's current state and the necessary data to formulate models for prediction. However, societal and natural events alter the course of a forest's development. A simulation environment that takes into account these events will facilitate forest management. In this thesis, we describe an efficient parallel implementation of a land cover use model, Mosaic, and discuss the development efforts to incorporate spatial interaction and succession dynamics into the model. To evaluate the performance of our implementation, an extensive set of simulation experiments was carried out using a dataset representing the H.J. Andrews Forest in the Oregon Cascades. Results indicate that a significant reduction in the simulation execution time of our parallel model can be achieved as compared to uni-processor simulations.
Date: August 2003
Creator: Mayes, John
Partner: UNT Libraries

Molecular Dynamics Simulations of the Structures and Properties of Aluminosilicate and Borosilicate Glasses

Description: Silicate glasses are the most common glass types and have impact on almost every aspect in our lives: from window, containers, to glass fibers for telecommunications. Unlike their crystalline counterparts, glass materials lack long-range order in their atomic arrangement but their structures do possess short and medium range characteristics that play critical roles in their physical and chemical properties. Despite active development of characterization techniques that have contributed to the understanding of glass structures, there remain key challenges in obtaining essential structural features of glasses. Atomistic computer simulations have become an increasingly important method in elucidating the atomic structures and in interpretation and/or prediction of composition-structure-property relationships of complex materials. In this dissertation, classical molecular dynamic (MD) simulations were used to investigate the atomic structures, dynamic and other properties of two important glass systems—aluminosilicate glasses and borosilicate glasses, which are the basis of most industrial and technologically important glasses. Firstly, a comprehensive study of peralkaline Na2O-Al2O3-SiO2 glass with varying Al2O3/SiO2, Na2O/Al2O3, Na2O/SiO2 ratios has been performed to obtain better understanding of the composition–structure–property relationships in this glass system. More than 99% of Al were 4-coordinated in these glasses, validating that Na+ tend to charge balance [AlO4]- network forming units first and then, excess Na+ was used to create non-bridging oxygen (NBO) on Si. As the drop of Na/Al ratio, the percentage of NBO decreases, indicating an increase of the glass network connectivity. In addition, polyhedral connection probability results show that Al tend to be randomly distributed in the glass structure, suggesting a violation of Lowenstein's rule. These structural properties were further used to explain macroscopic properties of glass, such as change of glass transition temperature (Tg) and hardness (Hv) with glass composition. Secondly, molecular dynamics simulations were used to understand the structural, thermal mechanical and diffusion behaviors of spodumene (LiAlSi2O6) ...
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Date: December 2018
Creator: Ren, Mengguo
Partner: UNT Libraries


Description: New York University, Courant Institute of Mathematical Sciences, participated in the “Fusion Simulation Program (FSP) Planning Activities” [http://www.pppl.gov/fsp], with C.S. Chang as the institutional PI. FSP’s mission was to enable scientific discovery of important new plasma phenomena with associated understanding that emerges only upon integration. This requires developing a predictive integrated simulation capability for magnetically-confined fusion plasmas that are properly validated against experiments in regimes relevant for producing practical fusion energy. Specific institutional goal of the New York University was to participate in the planning of the edge integrated simulation, with emphasis on the usage of large scale HPCs, in connection with the SciDAC CPES project which the PI was leading. New York University successfully completed its mission by participating in the various planning activities, including the edge physics integration, the edge science drivers, and the mathematical verification. The activity resulted in the combined report that can be found in http://www.pppl.gov/fsp/Overview.html. Participation and presentations as part of this project are listed in a separation file.
Date: June 5, 2012
Creator: Chang, Choong Seock
Partner: UNT Libraries Government Documents Department

Simulation Approaches for System of Systems: Event-Based versus Agent Based Modeling

Description: This paper from the 2015 Conference on Systems Engineering Research conference proceedings reviews different modeling techniques and uses two converse techniques, i.e. agent-based and event-based modeling, to run a simulation of hypothetical systems collaborating into a system of systems.
Date: March 16, 2015
Creator: Baldwin, W. Clifton; Sauser, Brian & Cloutier, Robert
Partner: UNT College of Business

Computer Simulation of Particulate Systems

Description: From Introduction: "The first objective of he present Bureau research was the development of a means to model random assemblies of circles and spheres that would accurately simulate actual particulate systems. The second objective of this research was to develop the computer simulations to the point where they could be used to predict real packaging or covering properties and to develop a body of data that could be used to improve and add to what is currently known about the statistical geometry of random particulate systems."
Date: 1971
Creator: Norman, Lindsay D.; Maust, Edwin E., Jr. & Skolnick, Leonard P.
Partner: UNT Libraries Government Documents Department

Simulating the Spread of Infectious Diseases in Heterogeneous Populations with Diverse Interactions Characteristics

Description: The spread of infectious diseases has been a public concern throughout human history. Historic recorded data has reported the severity of infectious disease epidemics in different ages. Ancient Greek physician Hippocrates was the first to analyze the correlation between diseases and their environment. Nowadays, health authorities are in charge of planning strategies that guarantee the welfare of citizens. The simulation of contagion scenarios contributes to the understanding of the epidemic behavior of diseases. Computational models facilitate the study of epidemics by integrating disease and population data to the simulation. The use of detailed demographic and geographic characteristics allows researchers to construct complex models that better resemble reality and the integration of these attributes permits us to understand the rules of interaction. The interaction of individuals with similar characteristics forms synthetic structures that depict clusters of interaction. The synthetic environments facilitate the study of the spread of infectious diseases in diverse scenarios. The characteristics of the population and the disease concurrently affect the local and global epidemic progression. Every cluster’ epidemic behavior constitutes the global epidemic for a clustered population. By understanding the correlation between structured populations and the spread of a disease, current dissertation research makes possible to identify risk groups of specific characteristics and devise containment strategies that facilitate health authorities to improve mitigation strategies.
Date: December 2013
Creator: Gomez-Lopez, Iris Nelly
Partner: UNT Libraries

List mode reconstruction for PET with motion compensation: A simulation study

Description: Motion artifacts can be a significant factor that limits the image quality in high-resolution PET. Surveillance systems have been developed to track the movements of the subject during a scan. Development of reconstruction algorithms that are able to compensate for the subject motion will increase the potential of PET. In this paper we present a list mode likelihood reconstruction algorithm with the ability of motion compensation. The subject moti is explicitly modeled in the likelihood function. The detections of each detector pair are modeled as a Poisson process with time vary ingrate function. The proposed method has several advantages over the existing methods. It uses all detected events and does not introduce any interpolation error. Computer simulations show that the proposed method can compensate simulated subject movements and that the reconstructed images have no visible motion artifacts.
Date: July 3, 2002
Creator: Qi, Jinyi & Huesman, Ronald H.
Partner: UNT Libraries Government Documents Department

List mode reconstruction for PET with motion compensation: A simulation study

Description: Motion artifacts can be a significant factor that limits the image quality in high-resolution PET. Surveillance systems have been developed to track the movements of the subject during a scan. Development of reconstruction algorithms that are able to compensate for the subject motion will increase the potential of PET. In this paper we present a list mode likelihood reconstruction algorithm with the ability of motion compensation. The subject motion is explicitly modeled in the likelihood function. The detections of each detector pair are modeled as a Poisson process with time-varying rate function. The proposed method has several advantages over the existing methods. It uses all detected events and does not introduce any interpolation error. Computer simulations show that the proposed method can compensate simulated subject movements and that the reconstructed images have no visible motion artifacts.
Date: July 1, 2002
Creator: Qi, Jinyi & Huesman, Ronald H.
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

Modeling and Simulation of Long-Term Performance of Near-Surface Barriers

Description: Society has and will continue to generate hazardous wastes whose risks must be managed. For exceptionally toxic, long-lived, and feared waste, the solution is deep burial, e.g., deep geological disposal at Yucca Mtn. For some waste, recycle or destruction/treatment is possible. The alternative for other wastes is storage at or near the ground level (in someone’s back yard); most of these storage sites include a surface barrier (cap) to prevent migration of the waste due to infiltration of surface water. The design lifespan for such barriers ranges from 30 to 1000 years, depending on hazard and regulations. In light of historical performance, society needs a better basis for predicting barrier performance over long time periods and tools for optimizing maintenance of barriers while in service. We believe that, as in other industries, better understanding of the dynamics of barrier system degradation will enable improved barriers (cheaper, longer-lived, simpler, easier to maintain) and improved maintenance. We are focusing our research on earthen caps, especially those with evapo-transpiration and capillary breaks. Typical cap assessments treat the barrier’s structure as static prior to some defined lifetime. Environmental boundary conditions such as precipitation and temperature are treated as time dependent. However, other key elements of the barrier system are regarded as constant, including engineered inputs (e.g., fire management strategy, irrigation, vegetation control), surface ecology (critical to assessment of plant transpiration), capillary break interface, material properties, surface erosion rate, etc. Further, to be conservative, only harmful processes are typically considered. A more holistic examination of both harmful and beneficial processes will provide more realistic pre-service prediction and in-service assessment of performance as well as provide designers a tool to encourage beneficial processes while discouraging harmful processes. Thus, the INEEL started a new project on long-term barrier integrity in April 2002 that aims to catalyze a ...
Date: February 1, 2003
Creator: Piet, Steven James; Jacobson, Jacob Jordan; Soto, Rafael; Martian, Pete & Martineau, Richard Charles
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

Anisoplanatic Performance of Horizontal-Path Speckle Imaging

Description: We have previously demonstrated and reported on the use of sub-field speckle processing for the enhancement of both near and far-range surveillance imagery of people and vehicles that have been degraded by atmospheric turbulence. We have obtained near diffraction-limited imagery in many cases and have shown dramatic image quality improvement in other cases. As it is possible to perform only a limited number of experiments in a limited number of conditions, we have developed a computer simulation capability to aid in the prediction of imaging performance in a wider variation of conditions. Our simulation capability includes the ability to model extended scenes in distributed turbulence. Of great interest is the effect of the isoplanatic angle on speckle imaging performance as well as on single deformable mirror and multiconjugate adaptive optics system performance. These angles are typically quite small over horizontal and slant paths. This paper will begin to explore these issues which are important for predicting the performance of both passive and active horizontal and slant-path imaging systems.
Date: July 1, 2003
Creator: Carrano, C J
Partner: UNT Libraries Government Documents Department

Multivariate Clustering of Large-Scale Simulation Data

Description: Simulations of complex scientific phenomena involve the execution of massively parallel computer programs. These simulation programs generate large-scale data sets over the spatiotemporal space. Modeling such massive data sets is an essential step in helping scientists discover new information from their computer simulations. In this paper, we present a simple but effective multivariate clustering algorithm for large-scale scientific simulation data sets. Our algorithm utilizes the cosine similarity measure to cluster the field variables in a data set. Field variables include all variables except the spatial (x, y, z) and temporal (time) variables. The exclusion of the spatial space is important since 'similar' characteristics could be located (spatially) far from each other. To scale our multivariate clustering algorithm for large-scale data sets, we take advantage of the geometrical properties of the cosine similarity measure. This allows us to reduce the modeling time from O(n{sup 2}) to O(n x g(f(u))), where n is the number of data points, f(u) is a function of the user-defined clustering threshold, and g(f(u)) is the number of data points satisfying the threshold f(u). We show that on average g(f(u)) is much less than n. Finally, even though spatial variables do not play a role in building a cluster, it is desirable to associate each cluster with its correct spatial space. To achieve this, we present a linking algorithm for connecting each cluster to the appropriate nodes of the data set's topology tree (where the spatial information of the data set is stored). Our experimental evaluations on two large-scale simulation data sets illustrate the value of our multivariate clustering and linking algorithms.
Date: March 4, 2003
Creator: Eliassi-Rad, T & Critchlow, T
Partner: UNT Libraries Government Documents Department

Implementations of mesh refinement schemes for particle-in-cell plasma simulations

Description: Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation region, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations and present two implementations in more detail, with examples.
Date: October 20, 2003
Creator: Vay, J. L.; Colella, P.; Friedman, A.; Grote, D. P.; McCorquodale, P. & Serafini, D. B.
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

Recombination Parameters in InGaAsSb Epitaxial Layers for Thermophotovoltaic Applications

Description: Radio-frequency (RF) photoreflectance measurements and one-dimensional device simulations have been used to evaluate bulk recombination parameter and surface recombination velocity (SRV) in doubly-capped 0.55 eV, 2 x 10{sup 17} cm{sup -3} doped p-InGaAsSb epitaxial layers for thermophotovoltaic (TPV) applications. Bulk lifetimes of 90-100 ns and SRVs of 680 cm/s to 3200 cm/s (depending on the capping layer) are obtained, with higher doping and higher bandgap capping layers most effective in reducing SRV. RF photoreflectance measurements and one-dimensional device simulations are compatible with a radiative recombination coefficient (B) of 3 x 10{sup -11} cm{sup 3}/s and Auger coefficient (C) of 1 x 10{sup -28} cm{sup 6}/s.
Date: March 17, 2003
Creator: Kumar, R.J.; Gutmann, J.J.; Borrego, J.M.; Dutta, P.S.; Wang, C.A.; Martinelli, R.U. et al.
Partner: UNT Libraries Government Documents Department

Rapid E-Learning Simulation Training and User Response

Description: A new trend in e-learning development is to have subject matter experts use rapid development tools to create training simulations. This type of training is called rapid e-learning simulation training. Though companies are using rapid development tools to create training quickly and cost effectively, there is little empirical research to indicate whether training created in this manner meets the needs of learners. The purpose of this study was to compare user responses to rapid e-learning simulation training to user responses receiving instructor-led training. The target population for this study was employees of a medium size private company in North America. Employees were divided into two groups and either received instructor-led training (comparison group) or received rapid e-learning simulation training (experimental group). The instrument used to measure user response was an adaptation of the technology acceptance model. Three variables were measured: training satisfaction, perceived ease of use, and perceived usefulness. Though no statistical significance was found between the two groups for training satisfaction and perceived usefulness, perceived ease of use was found to be statistically significant. Overall results fail to demonstrate the superiority of rapid e-learning simulation training over instructor-led training; however, this study indicates that rapid e-learning simulation training may be a viable substitute for classroom instruction based on user response.
Date: May 2011
Creator: Rackler, Angeline
Partner: UNT Libraries

Numerical Predictions for the Demo Enclosure and Comparison to Experiment

Description: The ''demo enclosure'' is a small box meant to simulate the basic characteristics of an equipment enclosure, but without the complexity of an actual enclosure. Extensive experimental measurements have been made on the enclosure and are summarized in a companion report entitled ''Experimental Measurements of the Demo Enclosure''. In this report, we will summarize the associated numerical modeling of the enclosure's structural vibration and radiated sound field using finite and boundary element techniques. One of the main goals of the report is to establish useful modeling guidelines for finite and boundary element analyses of enclosures. Producing accurate predictions is of primary importance, but ease of implementation is also important. We will try to demonstrate that it is not always beneficial to try to duplicate all the enclosure's structural complexity in the finite and boundary element models because errors inevitably occur and it is frequently difficult to adjust the models without considerable effort. For example, it is relatively simple to produce accurate models for shelves and enclosures separately, but their interconnections are much more difficult to represent. When the models are combined into much larger finite element models, it becomes difficult and time consuming to optimize the modeling of the interconnections. Our research was thus directed towards developing simple methods for adjusting the individual models and combining them together after an initial unite element analysis.
Date: February 5, 2004
Creator: Fahnline, JB; Campbell, RL & Hambric, SA
Partner: UNT Libraries Government Documents Department

PEBBLES Operation and Theory Manual

Description: The PEBBLES manual describes the PEBBLES code. The PEBBLES code is a computer program designed to simulation the motion, packing and vibration of spheres that undergo various mechanical forces including gravitation, Hooke’s law force and various friction forces. The frictional forces include true static friction that allows non-zero angles of repose. Each pebble is individually simulated using the distinct element method.
Date: September 1, 2010
Creator: Cogliati, Joshua J.
Partner: UNT Libraries Government Documents Department

Comparison of fast 3D simulation and actinic inspection for EUV masks with buries defects

Description: Aerial images for isolated defects and the interactions of defects with features are compared between the Actinic Inspection Tool (AIT) at Lawrence Berkeley National Laboratory (LBNL) and the fast EUV simulation program RADICAL. Comparisons between AIT images from August 2007 and RADICAL simulations are used to extract aberrations. At this time astigmatism was the dominant aberration with a value of 0.55 waves RMS. Significant improvements in the imaging performance of the AIT were made between August 2007 and December 2008. A good match will be shown between the most recent AIT images and RADICAL simulations without aberrations. These comparisons will demonstrate that a large defect, in this case 7nm tall on the surface, is still printable even if it is centered under the absorber line. These comparisons also suggest that the minimum defect size is between 1.5nm and 0.8nm surface height because a 1.5nm defect was printable but a 0.8nm was not. Finally, the image of a buried defect near an absorber line through focus will demonstrate an inversion in the effect of the defect from a protrusion of the dark line into the space to a protrusion of the space into the line.
Date: February 23, 2009
Creator: Clifford, C. H.; Wiraatmadja, S.; Chan, T. T.; Neureuther, A. R.; Goldberg, K. A.; Mochi, I. et al.
Partner: UNT Libraries Government Documents Department

Simplified models for mask roughness induced LER

Description: The ITRS requires < 1.2nm line-edge roughness (LER) for the 22nm half-pitch node. Currently, we can consistently achieve only about 3nm LER. Further progress requires understanding the principle causes of LER. Much work has already been done on how both the resist and LER on the mask effect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane, and factor into LER limits. Presently, mask-roughness induced LER is studied via full 2D aerial image modeling and subsequent analysis of the resulting image. This method is time consuming and cumbersome. It is, therefore, the goal of this research to develop a useful 'rule-of-thumb' analytic model for mask roughness induced LER to expedite learning and understanding.
Date: February 21, 2011
Creator: McClinton, Brittany & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department