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[Geometry, analysis, and computation in mathematics and applied science]. Progress report

Description: The principal investigators` work on a variety of pure and applied problems in Differential Geometry, Calculus of Variations and Mathematical Physics has been done in a computational laboratory and been based on interactive scientific computer graphics and high speed computation created by the principal investigators to study geometric interface problems in the physical sciences. We have developed software to simulate various physical phenomena from constrained plasma flow to the electron microscope imaging of the microstructure of compound materials, techniques for the visualization of geometric structures that has been used to make significant breakthroughs in the global theory of minimal surfaces, and graphics tools to study evolution processes, such as flow by mean curvature, while simultaneously developing the mathematical foundation of the subject. An increasingly important activity of the laboratory is to extend this environment in order to support and enhance scientific collaboration with researchers at other locations. Toward this end, the Center developed the GANGVideo distributed video software system and software methods for running lab-developed programs simultaneously on remote and local machines. Further, the Center operates a broadcast video network, running in parallel with the Center`s data networks, over which researchers can access stored video materials or view ongoing computations. The graphical front-end to GANGVideo can be used to make ``multi-media mail`` from both ``live`` computing sessions and stored materials without video editing. Currently, videotape is used as the delivery medium, but GANGVideo is compatible with future ``all-digital`` distribution systems. Thus as a byproduct of mathematical research, we are developing methods for scientific communication. But, most important, our research focuses on important scientific problems; the parallel development of computational and graphical tools is driven by scientific needs.
Date: February 1, 1994
Creator: Hoffman, D.
Partner: UNT Libraries Government Documents Department

A finite element analysis of room temperature silicon crystals for the advanced photon source bending-magnet and insertion-device beams

Description: In this paper, we give the results of a series of thermal and distortion finite element analyses performed on room temperature silicon for the three standard APS sources, namely, the bending magnet, Wiggler A, and Undulator A. The modeling was performed with the silicon cooled directly with water or liquid gallium through rectangular channels.
Date: October 1, 1994
Creator: Assoufid, L.; Lee, W.K. & Mills, D.
Partner: UNT Libraries Government Documents Department

Moving Bed Granular Bed Filter Development Program. Topical report, September 1994

Description: Five test arrangements have been designed to support the Granular Bed Filter Development Program as defined in the Test Plan. The first arrangement is a 3.6 ft. diameter half filter, with a glass covering along the cross section to allow visual examination of the granular alumina material passing through the filter. The second test arrangement is a 3.6 ft diameter full size filter having refractory lining to simulate actual surface roughness conditions. The third test arrangement will examine filter geometry scale up by testing a 6.0 ft. diameter full size filter. The fourth Test Arrangement consists of a small 12 inch diameter fluidizer to measure the minimum fluidization velocity of the 7 m (approx. size) alumina material to be used in the filter assemblies. The last Test Unit is used to evaluation relative abrasion characteristics of potential refractory and ceramic materials to be installed in high abrasion areas in the pneumatic transport piping.
Date: September 1, 1994
Creator: Haas, J.C.; Prudhomme, J.W. & Wilson, K.W.
Partner: UNT Libraries Government Documents Department

Differential geometry on Hopf algebras and quantum groups

Description: The differential geometry on a Hopf algebra is constructed, by using the basic axioms of Hopf algebras and noncommutative differential geometry. The space of generalized derivations on a Hopf algebra of functions is presented via the smash product, and used to define and discuss quantum Lie algebras and their properties. The Cartan calculus of the exterior derivative, Lie derivative, and inner derivation is found for both the universal and general differential calculi of an arbitrary Hopf algebra, and, by restricting to the quasitriangular case and using the numerical R-matrix formalism, the aforementioned structures for quantum groups are determined.
Date: December 15, 1994
Creator: Watts, P.
Partner: UNT Libraries Government Documents Department

Development of self-absorption coefficients for the determination of gamma-emitting radionuclides in environmental and mixed waste samples

Description: As the need for rapid and more accurate determinations of gamma-emitting radionuclides in environmental and mixed waste samples grows, there is continued interest in the development of theoretical tools to eliminate the need for some laboratory analyses and to enhance the quality of information from necessary analyses. In gamma spectrometry the use of theoretical self-absorption coefficients (SACs) can eliminate the need to determine the SAC empirically by counting a known source through each sample. This empirical approach requires extra counting time and introduces another source of counting error, which must be included in the calculation of results. The empirical determination of SACs is routinely used when the nuclides of interest are specified; theoretical determination of the SAC can enhance the information for the analysis of true unknowns, where there may be no prior knowledge about radionuclides present in a sample. Determination of an exact SAC does require knowledge about the total composition of a sample. In support of the Department of Energy`s (DOE) Environmental Survey Program, the Analytical Chemistry Laboratory (ACL) at Argonne National Laboratory developed theoretical self-absorption models to estimate SACs for the determination of non-specified radionuclides in samples of unknown, widely-varying, compositions. Subsequently, another SAC model, in a different counting geometry and for specified nuclides, was developed for another application. These two models are now used routinely for the determination of gamma-emitting radionuclides in a wide variety of environmental and mixed waste samples.
Date: May 1, 1994
Creator: Streets, W. E.
Partner: UNT Libraries Government Documents Department

A graphic view of Geometric Dimensioning and Tolerancing

Description: This paper points out a weakness frequently encountered in communication between Engineering Documents and Manufacturing Practices. In addition this paper gives an overview of a symbolic language designed to provide important communication between the Engineering Document and the Manufacturing process for every part and assembly. It will define the application of the characters used. Unlike the English language where the same word can have several meanings, the characters used in this symbolic language have only one.
Date: May 1, 1994
Creator: Swanson, R. A. C.
Partner: UNT Libraries Government Documents Department

Simulation of the GEM silicon central tracker using GEANT

Description: The silicon central tracker of the GEM detector has been simulated using the high energy physics simulations code GEANT. This paper will describe the level of detail of the geometry of the tracker that is in the code, including the silicon detectors themselves as well as all non-sensitive volumes such as support structures; the digitization, or detector response to particles, of the silicon detectors; the coordinate reconstruction from the digitizations, and some of the results of the simulations regarding the detector performance.
Date: January 1, 1994
Creator: Brooks, M. L. & Kinnison, W. W.
Partner: UNT Libraries Government Documents Department

Sorting and Hardware Assisted Rendering for Volume Visualization

Description: We present some techniques for volume rendering unstructured data. Interpolation between vertex colors and opacities is performed using hardware assisted texture mapping, and color is integrated for use with a volume rendering system. We also present an O(n{sup 2}) method for sorting n arbitrarily shaped convex polyhedra prior to visualization. It generalizes the Newell, Newell and Sancha sort for polygons to 3-D volume elements.
Date: March 1, 1994
Creator: Stein, C.; Becker, B. & Max, N.
Partner: UNT Libraries Government Documents Department

Linear-size nonobtuse triangulation of polygons

Description: We give an algorithm for triangulating n-vertex polygonal regions (with holes) so that no angle in the final triangulation measures more than {pi}/2. The number of triangles in the triangulation is only 0(n), improving a previous bound of 0(n{sup 2}), and the worst-case running time is 0(n log{sup 2} n). The basic technique used in the algorithm, recursive subdivision by disks, is new and may have wider application in mesh generation. We also report on an implementation of our algorithm.
Date: May 1, 1994
Creator: Bern, M.; Mitchell, S. & Ruppert, J.
Partner: UNT Libraries Government Documents Department

Geometry creation for MCNP by Sabrina and XSM

Description: The Monte Carlo N-Particle transport code MCNP is based on a surface description of 3-dimensional geometry. Cells are defined in terms of boolean operations on signed quadratic surfaces. MCNP geometry is entered as a card image file containing coefficients of the surface equations and a list of surfaces and operators describing cells. Several programs are available to assist in creation of the geometry specification, among them Sabrina and the new ``Smart Editor`` code XSM. We briefly describe geometry creation in Sabrina and then discuss XSM in detail. XSM is under development; our discussion is based on the state of XSM as of January 1, 1994.
Date: February 1, 1994
Creator: Van Riper, K. A.
Partner: UNT Libraries Government Documents Department

Criticality calculations with MCNP{trademark}: A primer

Description: With the closure of many experimental facilities, the nuclear criticality safety analyst increasingly is required to rely on computer calculations to identify safe limits for the handling and storage of fissile materials. However, in many cases, the analyst has little experience with the specific codes available at his/her facility. This primer will help you, the analyst, understand and use the MCNP Monte Carlo code for nuclear criticality safety analyses. It assumes that you have a college education in a technical field. There is no assumption of familiarity with Monte Carlo codes in general or with MCNP in particular. Appendix A gives an introduction to Monte Carlo techniques. The primer is designed to teach by example, with each example illustrating two or three features of MCNP that are useful in criticality analyses. Beginning with a Quickstart chapter, the primer gives an overview of the basic requirements for MCNP input and allows you to run a simple criticality problem with MCNP. This chapter is not designed to explain either the input or the MCNP options in detail; but rather it introduces basic concepts that are further explained in following chapters. Each chapter begins with a list of basic objectives that identify the goal of the chapter, and a list of the individual MCNP features that are covered in detail in the unique chapter example problems. It is expected that on completion of the primer you will be comfortable using MCNP in criticality calculations and will be capable of handling 80 to 90 percent of the situations that normally arise in a facility. The primer provides a set of basic input files that you can selectively modify to fit the particular problem at hand.
Date: June 6, 1994
Creator: Harmon, C. D. II; Busch, R. D.; Briesmeister, J. F. & Forster, R. A.
Partner: UNT Libraries Government Documents Department

Unified GUI for the Los Alamos Radiation Transport Code System

Description: Justine is a Unified Graphical User Interface (UGUI) which is used to define geometries using constructive solid geometric (CSG) operations on three-dimensional objects. These user defined geometries, along with other code specific parameters also controlled by Justine, are used by the Los Alamos Radiation Transport Code System (LARTCS), which includes the Radiation Transport Group`s (X-6) Monte Carlo and deterministic transport codes. Justine enhances user productivity, aids in code debugging, and enhances the reliability of the LARTCS.
Date: August 1, 1994
Creator: Lee, S. R.; Collins, D. G. & Anderson, J.
Partner: UNT Libraries Government Documents Department

Influence of electrode geometry on the high-field characteristics of photoconductive silicon wafers

Description: A series of experiment were conducted to study the influence of electrode geometry on the prebreakdown (and breakdown) characteristics of high resistivity ({rho} > 30 k{Omega}-cm), p-type Si wafers under quasi-uniform and non-uniform electric field configurations. In the quasi-uniform field configuration, the 1mm thick Si wafer was mounted between the slots of two plane parallel stainless steel disc electrodes (parallel), while the non-uniform field was obtained by mounting the wafer between two pillar-type electrodes with a hemispherical tip (pillar). The main objective of the above investigation was to verify if the uniform field configuration under a parallel system has a positive influence by reducing the field enhancement at the contact region, as opposed to the definite field enhancement present in the case of the non-uniform pillar system. Also, it was proposed to study the effect of the contact profile on the field distribution over the wafer surface and hence its influence on the high-field performance of the Si wafers.
Date: July 1, 1994
Creator: Madangarli, V. P.; Gradinaru, G.; Korony, G.; Sudarshan, T. S.; Loubriel, G. M.; Zutavern, F. J. et al.
Partner: UNT Libraries Government Documents Department

Effect of conductor geometry on source localization: Implications for epilepsy studies

Description: We shall discuss the effects of conductor geometry on source localization for applications in epilepsy studies. The most popular conductor model for clinical MEG studies is a homogeneous sphere. However, several studies have indicated that a sphere is a poor model for the head when the sources are deep, as is the case for epileptic foci in the mesial temporal lobe. We believe that replacing the spherical model with a more realistic one in the inverse fitting procedure will improve the accuracy of localizing epileptic sources. In order to include a realistic head model in the inverse problem, we must first solve the forward problem for the realistic conductor geometry. We create a conductor geometry model from MR images, and then solve the forward problem via a boundary integral equation for the electric potential due to a specified primary source. One the electric potential is known, the magnetic field can be calculated directly. The most time-intensive part of the problem is generating the conductor model; fortunately, this needs to be done only once for each patient. It takes little time to change the primary current and calculate a new magnetic field for use in the inverse fitting procedure. We present the results of a series of computer simulations in which we investigate the localization accuracy due to replacing the spherical model with the realistic head model in the inverse fitting procedure. The data to be fit consist of a computer generated magnetic field due to a known current dipole in a realistic head model, with added noise. We compare the localization errors when this field is fit using a spherical model to the fit using a realistic head model. Using a spherical model is comparable to what is usually done when localizing epileptic sources in humans, where the conductor model ...
Date: July 1, 1994
Creator: Schlitt, H.; Heller, L.; Best, E.; Ranken, D. & Aaron, R.
Partner: UNT Libraries Government Documents Department

Tomographic Reconstruction Based on Flexible Geometric Models

Description: When dealing with ill-posed inverse problems in data analysis, the Bayesian approach allows one to use prior information to guide the solution toward reasonable solutions. In this work the model consists of an object whose amplitude is constant inside a flexible boundary. The flexibility of the boundary is controlled by a distortion energy. We present an example of reconstruction of the cross section of a blood vessel from just two projections.
Date: August 1, 1994
Creator: Hanson, K. M.; Cunningham, G. S.; Jennings, G. R. Jr. & Wolf, D. R.
Partner: UNT Libraries Government Documents Department

Fixture and layout planning for reconfigurable workcells. LDRD final report

Description: The work in this program covered four primary areas: solid modeling, path planning, modular fixturing, and stability analysis. This report contains highlights of results from the program, references to published reports, and, in an appendix, a currently unpublished report which has been accepted for journal publication, but has yet to appear.
Date: June 1, 1994
Creator: Strip, D. & Phillips, C.
Partner: UNT Libraries Government Documents Department