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2,182 Matching Results
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A doubly logarithmic communication algorithm for the Completely Connected Optical Communication Parallel Computer
In this paper we consider the problem of interprocessor communication on a Completely Connected Optical Communication Parallel Computer (OCPC). The particular problem we study is that of realizing an h-relation. In this problem, each processor has at most h messages to send and at most h messages to receive. It is clear that any 1-relation can be realized in one communication step on an OCPC. However, the best known p-processor OCPC algorithm for realizing an arbitrary h-relation for h > 1 requires {Theta}(h + log p) expected communication steps. (This algorithm is due to Valiant and is based on earlier work of Anderson and Miller.) Valiant`s algorithm is optimal only for h = {Omega}(log p) and it is an open question of Gereb-Graus and Tsantilas whether there is a faster algorithm for h = o(log p). In this paper we answer this question in the affirmative by presenting a {Theta} (h + log log p) communication step algorithm that realizes an arbitrary h-relation on a p-processor OCPC. We show that if h {le} log p then the failure probability can be made as small as p{sup -{alpha}} for any positive constant {alpha}.
Date:
January 20, 1993
Creator:
Goldberg, L. A.; Jerrum, M.; Leighton, T. & Rao, S.
Object Type:
Article
System:
The UNT Digital Library
Communication on the Paragon
In this note the authors describe the results of some tests of the message-passing performance of the Intel Paragon. These tests have been carried out under both the Intel-supplied OSF/1 operating system with an NX library, and also under an operating system called SUNMOS (Sandia UNM Operating System). For comparison with the previous generation of Intel machines, they have also included the results on the Intel Touchstone Delta. The source code used for these tests is identical for all systems. As a result of these tests, the authors can conclude that SUNMOS demonstrates that the Intel Paragon hardware is capable of very high bandwidth communication, and that the message coprocessor on Paragon nodes can be used to give quite respectable latencies. Further tuning can be expected to yield even better performance.
Date:
October 15, 1993
Creator:
Greenberg, D.; Maccabe, B.; McCurley, K. S.; Riesen, R. & Wheat, S.
Object Type:
Report
System:
The UNT Digital Library
A Philosophical Study of the Holistic Paradigm with Heuristic Implications for Written Language
The problem of this study was to investigate the philosophical assumptions underlying the holistic paradigm. These underlying philosophical assumptions include beliefs about the nature of being (ontology), goals (axiology), and knowledge (epistemology). The interdependence of these assumptions, as well as how they translate into different research processes, is noted in this study.
Date:
December 1993
Creator:
Campbell, Carol L. (Carol Louise)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Risk communication in environmental restoration programs
The author advocates adoption of a convergence model in place of the traditional source-receiver model of communication for communicating with members of the public who have a stake in remediation of a nearby site. The source-receiver model conceives of communication as the transmission of a message from a risk management agency (sender) to a target audience of the public (receivers). The underlying theme is that the sender intends to change the perception of the receiver of either the issue or the sender of information. The theme may be appropriate for health campaigns which seek to change public behavior; however, the author draws on her experience at a DOE site undergoing remediation to illustrate why the convergence model is more appropriate in the context of cleanup. This alternative model focuses on the Latin derivation of communication as sharing or making common to many, i.e., as involving a relationship between participants who engage in a process of communication. The focus appears to be consistent with recently issued DOE policy that calls for involving the public in identifying issues and problems and in formulating and evaluating decision alternatives in cleanup. By emphasizing context, process and participants, as opposed to senders and receivers, the …
Date:
April 1, 1993
Creator:
Bradbury, J.A.
Object Type:
Article
System:
The UNT Digital Library
Risk communication in environmental restoration programs
The author advocates adoption of a convergence model in place of the traditional source-receiver model of communication for communicating with members of the public who have a stake in remediation of a nearby site. The source-receiver model conceives of communication as the transmission of a message from a risk management agency (sender) to a target audience of the public (receivers). The underlying theme is that the sender intends to change the perception of the receiver of either the issue or the sender of information. The theme may be appropriate for health campaigns which seek to change public behavior; however, the author draws on her experience at a DOE site undergoing remediation to illustrate why the convergence model is more appropriate in the context of cleanup. This alternative model focuses on the Latin derivation of communication as sharing or making common to many, i.e., as involving a relationship between participants who engage in a process of communication. The focus appears to be consistent with recently issued DOE policy that calls for involving the public in identifying issues and problems and in formulating and evaluating decision alternatives in cleanup. By emphasizing context, process and participants, as opposed to senders and receivers, the …
Date:
April 1, 1993
Creator:
Bradbury, J. A.
Object Type:
Article
System:
The UNT Digital Library
A lower bound for routing on a completely connected optical communication parallel computer
The task of routing a 2-relation on an n-processor completely connected optical communication parallel computer (OCPC) is considered. A lower bound is presented that applies to any randomized distributed algorithm for this task: specifically, it is shown that the expected number of steps required to route a 2-relation is {Omega}({radical} log log n) in the worst case. For comparison, the best upper bound known is O(log log n).
Date:
August 3, 1993
Creator:
Goldberg, L. A.; Jerrum, M. & MacKenzie, P. D.
Object Type:
Article
System:
The UNT Digital Library
A thermodynamic theory of dynamic fragmentation
We present a theory of dynamic fragmentation of brittle materials based on thermodynamic arguments. We recover the expressions for average fragment size and number as originally derived by Grady. We extend the previous work by obtaining descriptions of fragment size distribution and compressibility change due to the fragmentation process. The size distribution is assumed to be proportional to the spectral power of the strain history and a sample distribution is presented for a fragmentation process corresponding to a constant rate strain history. The description of compressibility change should be useful in computational studies of fragmentation. These results should provide insight into the process of fragmentation of brittle materials from hypervelocity impact.
Date:
August 1, 1993
Creator:
Yew, Ching H. & Taylor, P. A.
Object Type:
Article
System:
The UNT Digital Library
JAC Audio Interview: Donald Davidson
JAC interview of Donald Davidson discussing communicative interaction in relation to writing, philosophy, and rhetoric.
Date:
1993
Creator:
Kent, Thomas & Davidson, Donald, 1917-2003
Object Type:
Sound
System:
The UNT Digital Library
An efficient communication scheme for solving the S{sub n} equations on message-passing multiprocessors
Early models of Intel`s hypercube multiprocessors, e.g. the IPSC/I and iPSC/2, were characterized by the high latency of message-passing. This relatively weak dependence of the communication penalty on the size of messages, in contrast to its strong dependence on the number of messages, justified using the Fan-in Fan-out algorithm to perform global operations, such as global sums, etc. Recent models of message passing computers, such as the iPSC/860 and the Paragon, have been found to possess much smaller latency, thus forcing a re-examination of the issue of performance optimization with respect to communication schemes. Essentially, the Fan-in Fan-out scheme minimizes the number of nonsimultaneous messages sent but not the volume of data traffic across the network. Furthermore, if a global operation is performed in conjunction with the message-passing, a large fraction of the attached nodes remains idle as the number of utilized processors is halved in each step of the process. On the other hand, the Recursive Halving scheme offers the smallest communication cost for global operations, but has some drawbacks. First, it requires the simultaneous exchange of messages between adjacent nodes, which while permissible on many message-passing computers, requires additional programing on the iPSC/860, the target platform in this …
Date:
October 1, 1993
Creator:
Azmy, Y. Y.
Object Type:
Article
System:
The UNT Digital Library
Lattice Gas Hydrodynamics: Theory and Simulations
The first successful application of a microscopic analogy to create a skeleton cellular automaton and analyze it with statistical mechanical tools, was the work of Frisch, Hasslacher and Pomeau on the Navier-Stokes equation in two and three dimensions. This has become a very large research area with lattice gas models and methods being used for both fundamental investigations into the foundations of statistical mechanics and a large number of diverse applications. This present research was devoted to enlarging the fundamental scope of lattice gas models and proved successful. Since the beginning of this proposal, cellular automata have been constructed for statistical mechanical models, fluids, diffusion and shock systems in fundamental investigations. In applied areas, there are now excellent lattice gas models for complex flows through porous media, chemical reaction and combustion dynamics, multiphase flow systems, and fluid mixtures with natural boundaries. With extended cellular fluid models, one can do problems with arbitrary pairwise potentials. Recently, these have been applied to such problems as non-newtonian or polymeric liquids and a mixture of immiscible fluids passing through fractal or spongelike media in two and three dimensions. This proposal has contributed to and enlarged the scope of this work.
Date:
January 1, 1993
Creator:
Hasslacher, B.
Object Type:
Report
System:
The UNT Digital Library
Lattice gas hydrodynamics: Theory and simulations
The first successful application of a microscopic analogy to create a skeleton cellular automaton and analyze it with statistical mechanical tools, was the work of Frisch, Hasslacher and Pomeau on the Navier-Stokes equation in two and three dimensions. This has become a very large research area with lattice gas models and methods being used for both fundamental investigations into the foundations of statistical mechanics and a large number of diverse applications. This present research was devoted to enlarging the fundamental scope of lattice gas models and proved quite successful. Since the beginning of this proposal, cellular automata have been constructed for statistical mechanical models, fluids, diffusion and shock systems in fundamental investigations. In applied areas, there are now excellent lattice gas models for complex flows through porous media, chemical reaction and combustion dynamics, multiphase flow systems, and fluid mixtures with natural boundaries. With extended cellular fluid models, one can do problems with arbitrary pairwise potentials. Recently, these have been applied to such problems as non-newtonian or polymeric liquids and a mixture of immiscible fluids passing through fractal or spongelike media in two and three dimensions. This proposal has contributed to and enlarged the scope of this work.
Date:
January 1, 1993
Creator:
Hasslacher, B.
Object Type:
Report
System:
The UNT Digital Library
First Theory Institute on Computational Differentiation
Computational differentiation (CD) is concerned with tools, techniques, and mathematics for generating, with little human effort, efficient and accurate derivative codes from programs written in such computer languages as C and Fortran. The primary purposes of the meeting were to explore the deep complexity issues that lie at the heart of the computation of derivatives from computer programs and to provide a forum for brainstorming on future research directions, including the applications of automatic differentiation (AD) in scientific computing and the development of AD tools.
Date:
December 31, 1993
Creator:
Bischof, Christian H.; Griewank, Andreas & Khademi, Peyvand M.
Object Type:
Article
System:
The UNT Digital Library
Fusion Plasma Theory project summaries
This Project Summary book is a published compilation consisting of short descriptions of each project supported by the Fusion Plasma Theory and Computing Group of the Advanced Physics and Technology Division of the Department of Energy, Office of Fusion Energy. The summaries contained in this volume were written by the individual contractors with minimal editing by the Office of Fusion Energy. Previous summaries were published in February of 1982 and December of 1987. The Plasma Theory program is responsible for the development of concepts and models that describe and predict the behavior of a magnetically confined plasma. Emphasis is given to the modelling and understanding of the processes controlling transport of energy and particles in a toroidal plasma and supporting the design of the International Thermonuclear Experimental Reactor (ITER). A tokamak transport initiative was begun in 1989 to improve understanding of how energy and particles are lost from the plasma by mechanisms that transport them across field lines. The Plasma Theory program has actively-participated in this initiative. Recently, increased attention has been given to issues of importance to the proposed Tokamak Physics Experiment (TPX). Particular attention has been paid to containment and thermalization of fast alpha particles produced in a …
Date:
October 1, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Theory, modeling, and simulation annual report, 1992
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.
Date:
May 1, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Theory of the negative magnetoresistance in magnetic metallic multilayers
The Boltzman equation is solved for a system consisting of alternating ferromagnetic normal metallic layers. The in-plane conductance of the film is calculated for two configurations: successive ferromagnetic layers aligned parallel and antiparallel to each other. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by application of an extemal magnetic field. The calculation depends on geometric parameters (the thicknesses of the layers); intrinsic metal parameters (number of conduction electrons, magnetization and effective masses in the layers); bulk sample properties (conductivity relaxation times); and interface scattering properties (diffuse scattering versus potential scattering at the interfaces). It is found that a large negative magnetoresistance requires, in general, considerable asymmetry in the interface scattering for the two spin orienmtions. All qualitative features of the experiments are reproduced. Quantitative agreement can be achieved with sensible values of the parameters. The effect can be conceptually explained based on considerations of phase-space availability for an electron of a given spin orientation as it travels through the multilayer sample in the various configurations and traverses the interfaces.
Date:
April 1, 1993
Creator:
Hood, R. Q. & Falicov, L. M.
Object Type:
Article
System:
The UNT Digital Library
Application of semiclassical methods to reaction rate theory
This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. In SCTST, the Hamiltonian is expanded about the barrier and the ``good`` action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a …
Date:
November 1, 1993
Creator:
Hernandez, R.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
UST-ID robotics: Wireless communication and minimum conductor technology, and end-point tracking technology surveys
This report is a technology review of the current state-of-the-art in two technologies applicable to the Underground Storage Tank (UST) program at the Hanford Nuclear Reservation. The first review is of wireless and minimal conductor technologies for in-tank communications. The second review is of advanced concepts for independent tool-point tracking. This study addresses the need to provide wireless transmission media or minimum conductor technology for in-tank communications and robot control. At present, signals are conducted via contacting transmission media, i.e., cables. Replacing wires with radio frequencies or invisible light are commonplace in the communication industry. This technology will be evaluated for its applicability to the needs of robotics. Some of these options are radio signals, leaky coax, infrared, microwave, and optical fiber systems. Although optical fiber systems are contacting transmission media, they will be considered because of their ability to reduce the number of conductors. In this report we will identify, evaluate, and recommend the requirements for wireless and minimum conductor technology to replace the present cable system. The second section is a technology survey of concepts for independent end-point tracking (tracking the position of robot end effectors). The position of the end effector in current industrial robots is determined …
Date:
October 1, 1993
Creator:
Holliday, M. A.
Object Type:
Report
System:
The UNT Digital Library
Lattice gas hydrodynamics: Theory and simulations. Final report
The first successful application of a microscopic analogy to create a skeleton cellular automaton and analyze it with statistical mechanical tools, was the work of Frisch, Hasslacher and Pomeau on the Navier-Stokes equation in two and three dimensions. This has become a very large research area with lattice gas models and methods being used for both fundamental investigations into the foundations of statistical mechanics and a large number of diverse applications. This present research was devoted to enlarging the fundamental scope of lattice gas models and proved quite successful. Since the beginning of this proposal, cellular automata have been constructed for statistical mechanical models, fluids, diffusion and shock systems in fundamental investigations. In applied areas, there are now excellent lattice gas models for complex flows through porous media, chemical reaction and combustion dynamics, multiphase flow systems, and fluid mixtures with natural boundaries. With extended cellular fluid models, one can do problems with arbitrary pairwise potentials. Recently, these have been applied to such problems as non-newtonian or polymeric liquids and a mixture of immiscible fluids passing through fractal or spongelike media in two and three dimensions. This proposal has contributed to and enlarged the scope of this work.
Date:
May 1, 1993
Creator:
Hasslacher, B.
Object Type:
Report
System:
The UNT Digital Library
Fundamental theory of light for applications: Notes for five informal lectures
These notes give an overview of some aspects of the quantum theory of light and its interaction with matter. A description is given of basic emission and absorption processes, as well as the theory of photodetection and optical coherence. Basic research in this area is increasingly relevant to areas of technological importance, including microlaser devices and the noise characteristics of semiconductor lasers.
Date:
June 18, 1993
Creator:
Milonni, P.W.
Object Type:
Article
System:
The UNT Digital Library
Fundamental theory of light for applications: Notes for five informal lectures
These notes give an overview of some aspects of the quantum theory of light and its interaction with matter. A description is given of basic emission and absorption processes, as well as the theory of photodetection and optical coherence. Basic research in this area is increasingly relevant to areas of technological importance, including microlaser devices and the noise characteristics of semiconductor lasers.
Date:
June 18, 1993
Creator:
Milonni, P. W.
Object Type:
Article
System:
The UNT Digital Library
Modern integral equation techniques for quantum reactive scattering theory
Rigorous calculations of cross sections and rate constants for elementary gas phase chemical reactions are performed for comparison with experiment, to ensure that our picture of the chemical reaction is complete. We focus on the H/D+H{sub 2} {yields} H{sub 2}/DH + H reaction, and use the time independent integral equation technique in quantum reactive scattering theory. We examine the sensitivity of H+H{sub 2} state resolved integral cross sections {sigma}{sub v{prime}j{prime},vj}(E) for the transitions (v = 0,j = 0) to (v{prime} = 1,j{prime} = 1,3), to the difference between the Liu-Siegbahn-Truhlar-Horowitz (LSTH) and double many body expansion (DMBE) ab initio potential energy surfaces (PES). This sensitivity analysis is performed to determine the origin of a large discrepancy between experimental cross sections with sharply peaked energy dependence and theoretical ones with smooth energy dependence. We find that the LSTH and DMBE PESs give virtually identical cross sections, which lends credence to the theoretical energy dependence.
Date:
November 1, 1993
Creator:
Auerbach, S. M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Applications of Rapidly Mixing Markov Chains to Problems in Graph Theory
In this dissertation the results of Jerrum and Sinclair on the conductance of Markov chains are used to prove that almost all generalized Steinhaus graphs are rapidly mixing and an algorithm for the uniform generation of 2 - (4k + 1,4,1) cyclic Mendelsohn designs is developed.
Date:
August 1993
Creator:
Simmons, Dayton C. (Dayton Cooper)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Early Site Permit Demonstration Program: Recommendations for communication activities and public participation in the Early Site Permit Demonstration Program
On October 24, 1992, President Bush signed into law the National Energy Policy Act of 1992. The bill is a sweeping, comprehensive overhaul of the Nation`s energy laws, the first in more than a decade. Among other provisions, the National Energy Policy Act reforms the licensing process for new nuclear power plants by adopting a new approach developed by the US Nuclear Regulatory Commission (NRC) in 1989, and upheld in court in 1992. The NRC 10 CFR Part 52 rule is a three-step process that guarantees public participation at each step. The steps are: early site permit approval; standard design certifications; and, combined construction/operating licenses for nuclear power reactors. Licensing reform increases an organization`s ability to respond to future baseload electricity generation needs with less financial risk for ratepayers and the organization. Costly delays can be avoided because design, safety and siting issues will be resolved before a company starts to build a plant. Specifically, early site permit approval allows for site suitability and acceptability issues to be addressed prior to an organization`s commitment to build a plant. Responsibility for site-specific activities, including communications and public participation, rests with those organizations selected to try out early site approval. This plan …
Date:
January 27, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Theory of continuum damping of toroidal Alfven Eigenmodes in finite-{beta} tokamaks
We have formulated a general theoretical approach for analyzing two-dimensional structures of high-n Toroidal Alfven Eigenmodes (TAE) in large aspect-ratio, finite-{beta} tokamaks. Here, n is the toroidal wave number and {beta} is the ratio between plasma and magnetic pressures. The present approach generalizes the standard ballooning-mode formalism and is capable of treating eigenmodes with extended global radial structures as well as finite coupling between discrete and continuous spectra. Employing the well-known (s,{alpha}) model equilibrium and assuming a linear equilibrium profile, we have applied the present approach and calculated the corresponding resonant continuum damping rate of TAE modes. Here, s and {alpha} denote, respectively, the strengths of magnetic shear and pressure gradients. In particular, it is found that there exists a critical {alpha}{sub c}(s), such that, as {alpha} {yields} {alpha}{sub c}, the continuum damping rate is significantly enhanced and, thus, could suppress the potential TAE instability.
Date:
May 1993
Creator:
Zonca, F. & Chen, Liu
Object Type:
Report
System:
The UNT Digital Library