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Monopole Condensation and Confining Phase of N=1 Gauge Theories Via M Theory Fivebrane

Description: The fivebrane of M theory is used in order to study the moduli space of vacua of confining phase N=1 supersymmetric gauge theories in four dimensions. The supersymmetric vacua correspond to the condensation of massless monopoles and confinement of photons. The monopole and meson vacuum expectation values are computed using the fivebrane configuration. The comparison of the fivebrane computation and the field theory analysis shows that at vacua with a classically enhanced gauge group SU(r) the effective superpotential obtained by the"integrating in" method is exact for r=2 but is not exact for r> 2. The fivebrane configuration corresponding to N=1 gauge theories with Landau-Ginzburg type superpotentials is studied. N=1 non-trivial fixed points are analyzed using the brane geometry.
Date: August 7, 1997
Creator: de Boer, Jan & Oz, Yaron
Partner: UNT Libraries Government Documents Department

On the Geometry of the Quantum Poincare Group

Description: We review the construction of the multiparametric inhomogeneousorthogonal quantum group ISO{sub q,r}(N) as a projection from SO{sub q,r}(N+2), and recall the conjugation that for N=4 leads to the quantum Poincare group. We study the properties of the universal enveloping algebra U{sub q,r}(iso(N)), and give an R-matrix formlation. A quantum Lie algebra and a bicovariant differential calculus on twisted ISO(N) are found.
Date: May 1, 1997
Creator: Aschieri, P.
Partner: UNT Libraries Government Documents Department

Generation of multi-million element meshes for solid model-based geometries: The Dicer algorithm

Description: The Dicer algorithm generates a fine mesh by refining each element in a coarse all-hexahedral mesh generated by any existing all-hexahedral mesh generation algorithm. The fine mesh is geometry-conforming. Using existing all-hexahedral meshing algorithms to define the initial coarse mesh simplifies the overall meshing process and allows dicing to take advantage of improvements in other meshing algorithms immediately. The Dicer algorithm will be used to generate large meshes in support of the ASCI program. The authors also plan to use dicing as the basis for parallel mesh generation. Dicing strikes a careful balance between the interactive mesh generation and multi-million element mesh generation processes for complex 3D geometries, providing an efficient means for producing meshes of varying refinement once the coarse mesh is obtained.
Date: June 1, 1997
Creator: Melander, D.J.; Benzley, S.E. & Tautges, T.J.
Partner: UNT Libraries Government Documents Department

Refractive aiming corrections for satellite observation of stars

Description: Standard references describe how apparent zenith angles differ from true zenith angles for observers on the Earth. In fact, correction formulae are available for aiming Earth-based sensors at stars; some corrections give variations as a function of observer altitude. Such corrections have not been available for observers in space. This report develops formulae appropriate for proper aiming from space-based sensors toward the relatively few stars that are near the Earth`s limb at any given time. These formulae correct for refractive effects and may be critical for steerable space-borne sensors with fields of view less than one degree, tasked to observe starlight passing near the Earth`s surface. Ray tracing in the U.S. Standard Atmosphere, 1976 including H{sub 2}O effects, is used to determine relations between the refracted tangent height, the apparent tangent height resulting from observation at the sensor, and the angle through which the detected rays have deviated. Analytic fits of the ray deviation as a function of apparent tangent height allows quick determination of corrections needed for a space-borne sensor. Using those results that apply in the plane of incidence and using the necessary coordinate rotations, alterations in the star`s apparent right ascension and declination are evaluated to improve the aim. Examples illustrate that alterations can be larger than one degree, with effects lasting up to a few minutes.
Date: March 1, 1997
Creator: Vittitoe, C. N. & Schmidt, R. L.
Partner: UNT Libraries Government Documents Department

Geometric reasoning about assembly tools

Description: Planning for assembly requires reasoning about various tools used by humans, robots, or other automation to manipulate, attach, and test parts and subassemblies. This paper presents a general framework to represent and reason about geometric accessibility issues for a wide variety of such assembly tools. Central to the framework is a use volume encoding a minimum space that must be free in an assembly state to apply a given tool, and placement constraints on where that volume must be placed relative to the parts on which the tool acts. Determining whether a tool can be applied in a given assembly state is then reduced to an instance of the FINDPLACE problem. In addition, the author presents more efficient methods to integrate the framework into assembly planning. For tools that are applied either before or after their target parts are mated, one method pre-processes a single tool application for all possible states of assembly of a product in polynomial time, reducing all later state-tool queries to evaluations of a simple expression. For tools applied after their target parts are mated, a complementary method guarantees polynomial-time assembly planning. The author presents a wide variety of tools that can be described adequately using the approach, and surveys tool catalogs to determine coverage of standard tools. Finally, the author describes an implementation of the approach in an assembly planning system and experiments with a library of over one hundred manual and robotic tools and several complex assemblies.
Date: January 1, 1997
Creator: Wilson, R.H.
Partner: UNT Libraries Government Documents Department

Path planning for everday robotics with SANDROS

Description: We discuss the integration of the SANDROS path planner into a general robot simulation and control package with the inclusion of a fast geometry engine for distance calculations. This creates a single system that allows the path to be computed, simulated, and then executed on the physical robot. The architecture and usage procedures are presented. Also, we present examples of its usage in typical environments found in our organization. The resulting system is as easy to use as the general simulation system (which is in common use here) and is fast enough (example problems are solved in seconds) to be used interactively on an everyday basis.
Date: February 1, 1997
Creator: Watterberg, P.; Xavier, P. & Hwang, Y.
Partner: UNT Libraries Government Documents Department

Remote secure proof of identity using biometrics

Description: Biometric measurements derived from finger- or voiceprints, hand geometry, retinal vessel pattern and iris texture characteristics etc. can be identifiers of individuals. In each case, the measurements can be coded into a statistically unique bit-string for each individual. While in electronic commerce and other electronic transactions the proof of identity of an individual is provided by the use of either public key cryptography or biometric data, more secure applications can be achieved by employing both. However the former requires the use of exact bit patterns. An error correction procedure allows us to successfully combine the use of both to provide a general procedure for remote secure proof of identity using a generic biometric device. One such procedure has been demonstrated using a device based on hand geometry.
Date: June 10, 1997
Creator: Sengupta, S. K.; Pearson, P. & Strait, R.S.
Partner: UNT Libraries Government Documents Department

Effects of divertor geometry and pumping on plasma performance on DIII-D

Description: This paper reports the status of an ongoing investigation to discern the influence of the divertor and plasma geometry on the confinement of both ELM-free and ELMing discharges in DIII-D. The ultimate goal is to achieve a high-performance core plasma which coexists with an advanced divertor plasma. The divertor plasma must reduce the heat flux to acceptable levels; the current technique disperses the heat flux over a wide area by radiation (a radiative divertor). To date, we have obtained our best performance in double-null (DN) high-triangularity ({delta} {approximately} 0.8) ELM-free discharges. As discussed in detail elsewhere, there are several advantages for both the core and divertor plasma with highly-shaped DN operation. Previous radiative-divertor experiments with D{sub 2} injection in DN high-{delta} ELMing H-mode have shown that this configuration is more sensitive to gas puffing ({tau} decreases). Moving the X-point away from the target plate (to {approximately}15 cm above the plate) decreases this sensitivity. Preliminary measurements also indicate that gas puffing reduces the divertor heat flux but does not reduce the plasma pressure along the field line. The up/down heat flux balance can be varied magnetically (by changing the distance between the separatrices), with a slight magnetic imbalance required to balance the heat flux. The overall mission of the Radiative Divertor Project (RDP) is to install a fully pumped and baffled high-{delta} DN divertor. To date, however, both the DIII-D divertor diagnostics and pump were optimized for lower single-null (LSN) low-{delta} ({delta}{approximately} 0.4) plasmas, so much of the divertor physics has been performed in LSN; these results are discussed in Section 2. As part of the first phase of the RDP, we have installed a new high-{delta} USN divertor baffle and pump; these results are discussed in Section 3. Both divertor and core parameters are discussed in each case.
Date: June 1, 1997
Creator: Allen, S.L.; Hill, D.N. & Porter, G.D.
Partner: UNT Libraries Government Documents Department

The geometry of SU(3)

Description: The group SU(3) is parameterized in terms of generalized {open_quotes}Euler angles{close_quotes}. The differential operators of SU(3) corresponding to the Lie Algebra elements are obtained, the invariant forms are found, the group invariant volume element is found, and some relevant comments about the geometry of the group manifold are made.
Date: October 1, 1997
Creator: Byrd, M.
Partner: UNT Libraries Government Documents Department

Feature recognition applications in mesh generation

Description: The use of feature recognition as part of an overall decomposition-based hexahedral meshing approach is described in this paper. The meshing approach consists of feature recognition, using a c-loop or hybrid c-loop method, and the use of cutting surfaces to decompose the solid model. These steps are part of an iterative process, which proceeds either until no more features can be recognized or until the model has been completely decomposed into meshable sub-volumes. This method can greatly reduce the time required to generate an all-hexahedral mesh, either through the use of more efficient meshing algorithms on more of the geometry or by reducing the amount of manual decomposition required to mesh a volume.
Date: June 1, 1997
Creator: Tautges, T.J.; Liu, S.S.; Lu, Y.; Kraftcheck, J. & Gadh, R.
Partner: UNT Libraries Government Documents Department

A study of the process of using Pro/ENGINEER geometry models to create finite element models

Description: Methods for building Pro/ENGINEER models which allowed integration with structural and thermal mesh generation and analyses software without recreating geometry were evaluated. This study was not intended to be an in-depth study of the mechanics of Pro/ENGINEER or of mesh generation or analysis software, but instead was a first cut attempt to provide recommendations for Sandia personnel which would yield useful analytical models in less time than an analyst would require to create a separate model. The study evaluated a wide variety of geometries built in Pro/ENGINEER and provided general recommendations for designers, drafters, and analysts.
Date: February 1, 1997
Creator: Kistler, B.L.
Partner: UNT Libraries Government Documents Department

Data and image fusion for geometrical cloud characterization

Description: Clouds have a strong influence on the Earth`s climate and therefore on climate change. An important step in improving the accuracy of models that predict global climate change, general circulation models, is improving the parameterization of clouds and cloud-radiation interactions. Improvements in the next generation models will likely include the effect of cloud geometry on the cloud-radiation parameterizations. We have developed and report here methods for characterizing the geometrical features and three-dimensional properties of clouds that could be of significant value in developing these new parameterizations. We developed and report here a means of generating and imaging synthetic clouds which we used to test our characterization algorithms; a method for using Taylor`s hypotheses to infer spatial averages from temporal averages of cloud properties; a computer method for automatically classifying cloud types in an image; and a method for producing numerical three-dimensional renderings of cloud fields based on the fusion of ground-based and satellite images together with meteorological data.
Date: April 1, 1997
Creator: Thorne, L.R.; Buch, K.A.; Sun, Chen-Hui & Diegert, C.
Partner: UNT Libraries Government Documents Department

Advances in 3D electromagnetic finite element modeling

Description: Numerous advances in electromagnetic finite element analysis (FEA) have been made in recent years. The maturity of frequency domain and eigenmode calculations, and the growth of time domain applications is briefly reviewed. A high accuracy 3D electromagnetic finite element field solver employing quadratic hexahedral elements and quadratic mixed-order one-form basis functions will also be described. The solver is based on an object-oriented C++ class library. Test cases demonstrate that frequency errors less than 10 ppm can be achieved using modest workstations, and that the solutions have no contamination from spurious modes. The role of differential geometry and geometrical physics in finite element analysis is also discussed.
Date: August 1, 1997
Creator: Nelson, E.M.
Partner: UNT Libraries Government Documents Department

Performance of NDA techniques on a vitrified waste form

Description: Rocky Flats Environmental Technology Site (RFETS) is currently considering the use of vitrified transuranic (TRU)-waste forms for the final disposition of several waste materials. To date, however, little nondestructive assay (NDA) data have been acquired in the general NDA community to assist in this endeavor. This paper describes the efforts to determine constraints and operating parameters for using NDA instrumentation on vitrified waste. The present study was conducted on a sample composed of a plutonium-contaminated ash, similar to that found in the RFETS inventory, and a borosilicate-based glass. The vitrified waste item was fabricated at Los Alamos National Laboratory (LANL) using methods and equipment similar to those being proposed by RFETS to treat their ash material. The focus of this study centered on the segmented gamma scanner (SGS) with 1/2-inch collimation, a technique that is presently available at RFETS. The accuracy and precision of SGS technology was evaluated, with particular attention to bias issues involving matrix geometry, homogeneity, and attenuation. Tomographic gamma scanning was utilized in the determination of the waste form homogeneity. A thermal neutron technique was also investigated and comparisons made with the gamma results.
Date: November 1, 1997
Creator: Hurd, J.R.; Veazey, G.W.; Prettyman, T.H.; Mercer, D.J.; Ricketts, T.E. & Nakaoka, R.K.
Partner: UNT Libraries Government Documents Department


Description: This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range ...
Date: September 23, 1997
Partner: UNT Libraries Government Documents Department

Fifth SIAM conference on geometric design 97: Final program and abstracts. Final technical report

Description: The meeting was divided into the following sessions: (1) CAD/CAM; (2) Curve/Surface Design; (3) Geometric Algorithms; (4) Multiresolution Methods; (5) Robotics; (6) Solid Modeling; and (7) Visualization. This report contains the abstracts of papers presented at the meeting. Proceding the conference there was a short course entitled ``Wavelets for Geometric Modeling and Computer Graphics``.
Date: December 31, 1997
Partner: UNT Libraries Government Documents Department

Compartmentalization analysis using discrete fracture network models

Description: This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.
Date: December 31, 1997
Creator: La Pointe, P.R.; Eiben, T.; Dershowitz, W. & Wadleigh, E.
Partner: UNT Libraries Government Documents Department

Microseismic and deformation imaging of hydraulic fracture growth and geometry in the C sand interval, GRI/DOE M-Site project

Description: Six hydraulic-fracture injections into a fluvial sandstone at a depth of 4300 ft were monitored with multi-level tri-axial seismic receivers in two wells and an inclinometer array in one well, resulting in maps of the growth and final geometry of each fracture injection. These diagnostic images show the progression of height and length growth with fluid volume, rate and viscosity. Complexities associated with shut downs and high treatment pressures can be observed. Validation of the seismic geometry was made with the inclinometers and diagnostic procedures in an intersecting well. Fracture information related to deformation, such as fracture closure pressure, residual widths, and final prop distribution, were obtained from the inclinometer data.
Date: August 1, 1997
Creator: Warpinski, N.R.; Uhl, J.E. & Engler, B.P.
Partner: UNT Libraries Government Documents Department

Good terrain geometry, cheap!

Description: Real-time terrain rendering for interactive visualization remains a demanding task. We present a novel algorithm with several advantages over previous methods: our method is unusually stingy with polygons yet achieves real-time performance and is scalable to arbitrary regions and resolutions. The method provides a continuous terrain mesh of specified triangle count having provably minimum error in restricted but reasonably general classes of permissible meshes and error metrics. Our method provides an elegant solution to guaranteeing certain elusive types of consistency in scenes produced by multiple scene generators which share a common finest-resolution database but which otherwise operate entirely independently. This consistency is achieved by exploiting the freedom of choice of error metric allowed by the algorithm to provide, for example, multiple exact lines-of-sight in real-time. Our methods rely on an off-line pre-processing phase to construct a multi-scale data structure consisting of triangular terrain approximations enhanced ({open_quotes}thickened{close_quotes}) with world-space error information. In real time, this error data is efficiently transformed into screen-space where it is used to guide a greedy top-down triangle subdivision algorithm which produces the desired minimal error continuous terrain mesh. Our algorithm has been implemented and it operates at real-time rates.
Date: April 1, 1997
Creator: Duchaineau, M.; Wolinsky, M. & Sigeti, D.E.
Partner: UNT Libraries Government Documents Department

Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

Description: Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-950l. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate the viscoelastic based model show that the observed characteristic behavior is captured by this model.
Date: July 1, 1997
Creator: Browning, R.V. & Scammon, R.J.
Partner: UNT Libraries Government Documents Department

Analysis of classical transport equations for the Tokamak edge plasma

Description: The classical fluid transport equations for a magnet-plasma as given, for example, by Braginskii [1], are complicated in their most general form. Here we obtain the simplest reduced set which contains the essential physics of the tokamak edge problem in slab geometry by systematically applying a parameter ordering and making use of specific symmetries. An important ingredient is a consistent set of boundary conditions as described elsewhere [2]. This model clearly resolves some important issues concerning diamagnetic drifts, high parallel viscosity, and the ambipolarity constraint. The final equations can also serve as a model for understanding the structure of the equations in the presence of anomalous transport terms arising from fluctuations. In fact, Braginskii-like equations are the basis of a number of scrape-off layer (SOL) transport codes [3]. However, all of these codes contain ad hoc radial diffusion terms and often neglect some classical terms, both of which make the self-consistency of the models questionable. Braginskii's equations [1] have been derived from the first principles via the kinetic equations and, thereby, contain such ''built-in'' features as the symmetry of kinetic coefficients, and automatic quasineutrality of a cross-field diffusion in a system with toroidal symmetry such as a tokamak. Our model thus maintains these properties.
Date: September 29, 1997
Creator: Rognlien, T. D., LLNL
Partner: UNT Libraries Government Documents Department

Human supervisory approach to modeling industrial scenes using geometric primitives

Description: A three-dimensional world model is crucial for many robotic tasks. Modeling techniques tend to be either fully manual or autonomous. Manual methods are extremely time consuming but also highly accurate and flexible. Autonomous techniques are fast but inflexible and, with real-world data, often inaccurate. The method presented in this paper combines the two, yielding a highly efficient, flexible, and accurate mapping tool. The segmentation and modeling algorithms that compose the method are specifically designed for industrial environments, and are described in detail. A mapping system based on these algorithms has been designed. It enables a human supervisor to quickly construct a fully defined world model from unfiltered and unsegmented real-world range imagery. Examples of how industrial scenes are modeled with the mapping system are provided.
Date: November 19, 1997
Creator: Luck, J.P.; Little, C.Q. & Roberts, R.S.
Partner: UNT Libraries Government Documents Department