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Collective communication routines in PVM

Description: The collective communication routines of scatter, gather, and reduce are frequently implemented as part of the native library for parallel architectures. These operations have been implemented in PVM for use among a heterogeneous system of workstations and parallel computers forming a virtual parallel machine. In the case of the Intel Paragon machines, the PVM implementation of the reduce operation utilizes the corresponding native mode library routines whenever possible. This paper describes the implementation of these collective communication routines in PVM including the utilization of the Intel Paragon native mode operations. Performance data is also given comparing the use of the native Intel Paragon collective routines and the PVM implementation on top of these routines on a dedicated Intel Paragon. For our timing results an average latency of 109 {mu}s is incurred using PVM as compared to the native Intel global sum routine. This extra startup is independent of the size of the message being sent and the number of nodes in the group. It is demonstrated that the use of static groups is preferable in time efficiency over the use of dynamic groups.
Date: May 1, 1996
Creator: Donato, J.M. & Geist, G.A.
Partner: UNT Libraries Government Documents Department

The Financial Management Environment (FaME): A prototype interactive hypertext-based financial planning and reporting system

Description: It is critical in every government, research, and industrial organization that accurate and timely financial information be made available at all levels so that, project and business decisions can be made within funding constraints. The FaME prototype implemented at Oak Ridge National Laboratory extracts financial data from a legacy system, builds easy-to-understand reports and graphs, and presents them on-line so that people at all levels in an organization can assess the financial status of individual projects or entire organizations. Reports are presented in hypertext and graphical formats that can be read with popular World Wide Web browsers such as NCSA Mosaic or Netscape. All reports are hyper-linked in a natural way to simplify navigation and information retrieval. To protect potentially sensitive information, FAME provides access control so that individuals can retrieve only the information that is required for them to carry out their financial duties. In addition to the reports and graphs, FAME includes budget building tools to provide for financial planning. Another primary feature is that the prototype 1 utilizes equipment that already exists on the user`s desktop. The overall goal of the FAME system is to provide users with precise and meaningful information on the financial status of an organization or project at a glance.
Date: November 1, 1995
Creator: Barnes, K.D.; Donato, J.M. & Flanagan, D.M.
Partner: UNT Libraries Government Documents Department

Visualization for the Large Scale Data Analysis Project

Description: In this paper the authors overview the visualization approach used as part of the Large Scale Data Analysis project. This project used the AVS5 software to create interface tools for the public domain database management system POSTGRES. This work utilized hardware and software available through the AVRC. This work is part of ongoing research on data analysis tools for large (terabyte) data sets. Statistical analysis and browsing tools for the data sets were implemented as part of an AVS5 software system network which interfaces to the POSTGRES database management system. These networks were implemented to provide uniform graphical interfaces for both the feature extraction stage and the post processing stage of the entire system. The network of tools for these interfaces, rather than the statistical tools themselves, are the focus of this paper.
Date: April 1, 1996
Creator: Flanery, R.E. Jr. & Donato, J.M.
Partner: UNT Libraries Government Documents Department

Coefficient adaptive triangulation for strongly anisotropic problems

Description: Second order elliptic partial differential equations arise in many important applications, including flow through porous media, heat conduction, the distribution of electrical or magnetic potential. The prototype is the Laplace problem, which in discrete form produces a coefficient matrix that is relatively easy to solve in a regular domain. However, the presence of anisotropy produces a matrix whose condition number is increased, making the resulting linear system more difficult to solve. In this work, we take the anisotropy into account in the discretization by mapping each anisotropic region into a ``stretched`` coordinate space in which the anisotropy is removed. The region is then uniformly triangulated, and the resulting triangulation mapped back to the original space. The effect is to generate long slender triangles that are oriented in the direction of ``preferred flow.`` Slender triangles are generally regarded as numerically undesirable since they tend to cause poor conditioning; however, our triangulation has the effect of producing effective isotropy, thus improving the condition number of the resulting coefficient matrix.
Date: January 1, 1996
Creator: D`Azevedo, E.F.; Romine, C.H. & Donato, J.M.
Partner: UNT Libraries Government Documents Department

Modeling of dynamical processes in laser ablation

Description: Various physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed-laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume, plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms, hydrodynamic and collisional descriptions of plume transport, and molecular dynamics models of the interaction of plume particles with the deposition substrate.
Date: December 31, 1995
Creator: Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A. et al.
Partner: UNT Libraries Government Documents Department

Modeling of plume dynamics in laser ablation processes for thin film deposition of materials

Description: The transport dynamics of laser-ablated neutral/plasma plumes are of significant interest for film growth by pulsed-laser deposition of materials since the magnitude and kinetic energy of the species arriving at the deposition substrate are key processing parameters. Dynamical calculations of plume propagation in vacuum and in background gas have been performed using particle-in-cell hydrodynamics, continuum gas dynamics, and scattering models. Results from these calculations are presented and compared with experimental observations.
Date: December 31, 1995
Creator: Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A. et al.
Partner: UNT Libraries Government Documents Department

Modeling of thermal, electronic, hydrodynamic, and dynamic deposition processes for pulsed-laser deposition of thin films

Description: Various physical processes during laser ablation of solids for pulsed-laser deposition (PLD) are studied using a variety of computational techniques. In the course of the authors combined theoretical and experimental effort, they have been trying to work on as many aspects of PLD processes as possible, but with special focus on the following areas: (a) the effects of collisional interactions between the particles in the plume and in the background on the evolving flow field and on thin film growth, (b) interactions between the energetic particles and the growing thin films and their effects on film quality, (c) rapid phase transformations through the liquid and vapor phases under possibly nonequilibrium thermodynamic conditions induced by laser-solid interactions, (d) breakdown of the vapor into a plasma in the early stages of ablation through both electronic and photoionization processes, (c) hydrodynamic behavior of the vapor/plasma during and after ablation. The computational techniques used include finite difference (FD) methods, particle-in-cell model, and atomistic simulations using molecular dynamics (MD) techniques.
Date: November 1, 1994
Creator: Liu, C.L.; LeBoeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Chen, K.R. et al.
Partner: UNT Libraries Government Documents Department

Mining multi-dimensional data for decision support

Description: While it is widely recognized that data can be a valuable resource for any organization, extracting information contained within the data is often a difficult problem. Attempts to obtain information from data may be limited by legacy data storage formats, lack of expert knowledge about the data, difficulty in viewing the data, or the volume of data needing to be processed. The rapidly developing field of Data Mining or Knowledge Data Discovery is a blending of Artificial Intelligence, Statistics, and Human-Computer Interaction. Sophisticated data navigation tools to obtain the information needed for decision support do not yet exist. Each data mining task requires a custom solution that depends upon the character and quantity of the data. This paper presents a two-stage approach for handling the prediction of personal bankruptcy using credit card account data, combining decision tree and artificial neural network technologies. Topics to be discussed include the pre-processing of data, including data cleansing, the filtering of data for pertinent records, and the reduction of data for attributes contributing to the prediction of bankruptcy, and the two steps in the mining process itself.
Date: June 1, 1998
Creator: Donato, J.M.; Schryver, J.C.; Hinkel, G.C.; Schmoyer, R.L. Jr.; Grady, N.W. & Leuze, M.R.
Partner: UNT Libraries Government Documents Department

Mechanisms affecting kinetic energies of laser-ablated materials

Description: Laser materials processing techniques are expected to have a dramatic impact on materials science and engineering in the near future and beyond. One of the main laser materials processing techniques is Pulsed Laser Deposition (PLD) for thin film growth. While experimentalists search for optimal approaches for thin film growth with pulsed laser deposition (PLD), a systematic effort in theory and modeling of various processes during PLD is needed. The quality of film deposited depends critically on the range and profile of the kinetic energy and density of the ablated plume. While it is to the advantage of pulsed laser deposition to have high kinetic energy, plumes that are too energetic causes film damage. A dynamic source effect was found to accelerate the plume expansion velocity much higher than that from a conventional free expansion model. A self-similar theory and a hydrodynamic model are developed to study this effect, which may help to explain experimentally observed high front expansion velocity. Background gas can also affect the kinetic energies. High background gas may cause the ablated materials to go backward. Experimentally observed plume splitting is also discussed.
Date: December 1995
Creator: Chen, K. R.; Leboeuf, J. N.; Wood, R. F.; Geohegan, D. B.; Donato, J. M.; Liu, C. L. et al.
Partner: UNT Libraries Government Documents Department

Vapor breakdown during ablation by nanosecond laser pulses

Description: Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no attempts made on vapor breakdown by nanosecond laser pulses. This work intends to fill the gap. A kinetic model is developed considering following factors: (1) two temperatures of both electrons and heavy-body particles (ions, neutrals, and excited states of neutrals), (2) absorption mechanisms of laser energy include inverse bremstrahlung (IB) processes and photoionization of excited states, (3) ionization acceleration mechanisms included are electron-impact excitation of ground state neutrals, electron-impact ionization of exited states of neutrals, photoionization of excited states of neutrals, and all necessary reverse processes. The rates of various processes considered are calculated according to the formula given by Zel`dovich and Raizer. The authors use a second order predictor-corrector numerical scheme for iterations of the rate equations. The rate equations are solved for five quantities, namely, densities of electrons, neutrals, and excited states of neutrals, and the temperatures of electrons and heavy-body particles. The total breakdown times (sum of evaporation time and vapor breakdown time) at different energy fluences are then calculated. The results are compared with experimental observations of Si target ablation using a KrF laser. A more detailed description of the model and the results will be published later.
Date: April 1, 1995
Creator: Liu, C.L.; Leboeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Chen, K.R. et al.
Partner: UNT Libraries Government Documents Department

Dynamical modeling of laser ablation processes

Description: Several physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume; plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.
Date: September 1, 1995
Creator: Leboeuf, J. N.; Chen, K. R.; Donato, J. M.; Geohegan, D. B.; Liu, C. L.; Puretzky, A. A. et al.
Partner: UNT Libraries Government Documents Department

Laser-solid interaction and dynamics of laser-ablated materials

Description: An annealing model is extended to treat the vaporization process, and a hydrodynamic model describes the ablated material. We find that dynamic source and ionization effects accelerate the expansion front of the ablated plume with thermal vaporization temperature. The vaporization process and plume propagation in high background gas pressure are studied.
Date: September 1995
Creator: Chen, K. R.; Neboeuf, J. N.; Wood, R. F.; Geohegan, D. B.; Donato, J. M.; Liu, C. L. et al.
Partner: UNT Libraries Government Documents Department

Laser-solid interaction and dynamics of the laser-ablated materials

Description: Rapid transformations through the liquid and vapor phases induced by laser-solid interactions are described by the authors` thermal model with the Clausius-Clapeyron equation to determine the vaporization temperature under different surface pressure condition. Hydrodynamic behavior of the vapor during and after ablation is described by gas dynamic equations. These two models are coupled. Modeling results show that lower background pressure results lower laser energy density threshold for vaporization. The ablation rate and the amount of materials removed are proportional to the laser energy density above its threshold. The authors also demonstrate a dynamic source effect that accelerates the unsteady expansion of laser-ablated material in the direction perpendicular to the solid. A dynamic partial ionization effect is studied as well. A self-similar theory shows that the maximum expansion velocity is proportional to c{sub s}{alpha}, where 1 {minus} {alpha} is the slope of the velocity profile. Numerical hydrodynamic modeling is in good agreement with the theory. With these effects, {alpha} is reduced. Therefore, the expansion front velocity is significantly higher than that from conventional models. The results are consistent with experiments. They further study how the plume propagates in high background gas condition. Under appropriate conditions, the plume is slowed down, separates with the background, is backward moving, and hits the solid surface. Then, it splits into two parts when it rebounds from the surface. The results from the modeling will be compared with experimental observations where possible.
Date: July 1, 1995
Creator: Chen, K. R.; Leboeuf, J. N.; Geohegan, D. B.; Wood, R. F.; Donato, J. M.; Liu, C. L. et al.
Partner: UNT Libraries Government Documents Department