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Analysis of the Effect of Geometry Generated Turbulence on HCCI Combustion by Multi-Zone Modeling

Description: This paper illustrates the applicability of a sequential fluid mechanics, multi-zone chemical kinetics model to analyze HCCI experimental data for two combustion chamber geometries with different levels of turbulence: a low turbulence disc geometry (flat top piston), and a high turbulence square geometry (piston with a square bowl). The model uses a fluid mechanics code to determine temperature histories in the engine as a function of crank angle. These temperature histories are then fed into a chemical kinetic solver, which determines combustion characteristics for a relatively small number of zones (40). The model makes the assumption that there is no direct linking between turbulence and combustion. The results show that the multi-zone model yields good results for both the disc and the square geometries. The model makes good predictions of pressure traces and heat release rates. The experimental results indicate that the high turbulence square geometry has longer burn duration than the low turbulence disc geometry. This difference can be explained by the sequential multi-zone model, which indicates that the cylinder with the square bowl has a thicker boundary layer that results in a broader temperature distribution. This broader temperature distribution tends to lengthen the combustion, as cold mass within the cylinder takes longer to reach ignition temperature when compressed by the expansion of the first burned gases. The multi-zone model, which makes the basic assumption that HCCI combustion is controlled by chemical kinetics, is therefore capable of explaining the experimental results obtained for different levels of turbulence, without considering a direct interaction between turbulence and combustion. A direct connection between turbulence and HCCI combustion may still exists, but it seems to play a relatively minor role in determining burn duration at the conditions analyzed in this paper.
Date: December 13, 2004
Creator: Aceves, S M; Flowers, D L; Martinez-Frias, J; Espinosa-Loza, F; Christensen, M; Johansson, B et al.
Partner: UNT Libraries Government Documents Department

Realizing the Opportunities of Neutron Cross Section Measurements at RIA

Description: The Rare Isotope Accelerator will produce many isotopes at never before seen rates. This will allow for the first time measurements on isotopes very far from stability and new measurement opportunities for unstable nuclei near stability. In fact, the production rates are such that it should be possible to collect 10 micrograms of many isotopes with a half-life of 1 day or more. This ability to make targets of short-lived nuclei enables the possibility of making neutron cross-section measurements important to the astrophysics and the stockpile stewardship communities. But to fully realize this opportunity, the appropriate infrastructure must be included at the RIA facility. This includes isotope harvesting capabilities, radiochemical areas for processing collected material, and an intense, ''mono-energetic'', tunable neutron source. As such, we have been developing a design for neutron source facility to be included at the RIA site. This facility would produce neutrons via intense beams of deuterons and protons on a variety of targets. The facility would also include the necessary radiochemical facilities for target processing. These infrastructure needs will be discussed in addition to the methods that would be employed at RIA for measuring these neutron cross-sections.
Date: October 13, 2004
Creator: Ahle, L; Hausmann, M; Reifarth, R; Roberts, K; Roeben, M; Rusnak, B et al.
Partner: UNT Libraries Government Documents Department

Automatic registration of serial mammary gland sections

Description: We present two new methods for automatic registration of microscope images of consecutive tissue sections. They represent two possibilities for the first step in the 3-D reconstruction of histological structures from serially sectioned tissue blocks. The goal is to accurately align the sections in order to place every relevant shape contained in each image in front of its corresponding shape in the following section before detecting the structures of interest and rendering them in 3D. This is accomplished by finding the best rigid body transformation (translation and rotation) of the image being registered by maximizing a matching function based on the image content correlation. The first method makes use of the entire image information, whereas the second one uses only the information located at specific sites, as determined by the segmentation of the most relevant tissue structures. To reduce computing time, we use a multiresolution pyramidal approach that reaches the best registration transformation in increasing resolution steps. In each step, a subsampled version of the images is used. Both methods rely on a binary image which is a thresholded version of the Sobel gradients of the image (first method) or a set of boundaries manually or automatically obtained that define important histological structures of the sections. Then distance-transform of the binary image is computed. A proximity function is then calculated between the distance image of the image being registered and that of the reference image. The transformation providing a maximum of the proximity function is then used as the starting point of the following step. This is iterated until the registration error lies below a minimum value.
Date: April 13, 2004
Creator: Arganda-Carreras, Ignacio; Fernandez-Gonzalez, Rodrigo & Ortiz-de-Solorzano, Carlos
Partner: UNT Libraries Government Documents Department

RECENT RESULTS FROM OPTIMIZATION STUDIES OF LINEAR NON-SCALING FFAGs FOR MUON ACCELERATION.

Description: Because of the highly repetitive nature and simple cell structure of FFAG lattices, it is possible to automatically design these lattices. In designing an FFAG lattice, one will try to meet certain constraints and then minimize some cost function by varying any remaining free parameters. I will first review previously published work on optimized FFAG design. Then I will describe recent advances in the understanding of linear non-scaling FFAG design that have come from these optimization techniques. I will describe how the lattice designs depend on some input parameters to the design. Finally, I will present a set of FFAG lattices that are optimized for muon acceleration using these techniques.
Date: October 13, 2004
Creator: BERG,J.S.
Partner: UNT Libraries Government Documents Department

Global analysis of inclusive B decays

Description: In light of the large amount of new experimental data, we revisit the determination of |V{sub cb}| and m{sub b} from inclusive semileptonic and radiative B decays. We study shape variables to order {Lambda}{sub QCD}{sup 3}/m{sub b}{sup 3} and {alpha}{sub s}{sup 2}{beta}{sub 0}, and include the order {alpha}{sub s} {Lambda}{sub QCD}/m{sub b} correction to the hadron mass spectrum in semileptonic decay, which improves the agreement with the data. We focus on the 1S and kinetic mass schemes for the b quark, with and without expanding m{sub b}-m{sub c} in HQET. We perform fits to all available data from BABAR, BELLE, CDF, CLEO, and DELPHI, discuss the theoretical uncertainties, and compare with earlier results. We find |V{sub cb}| = (41.9 {+-} 0.6 {+-} 0.1{sub {tau}{sub B}}) x 10{sup -3} and m{sub b}{sup 1S} = 4.68 {+-} 0.04GeV, including our estimate of the theoretical uncertainty in the fit.
Date: August 13, 2004
Creator: Bauer, Christian W.; Ligeti, Zoltan; Luke, Michael; Manohar, Aneesh & Trott, Michael
Partner: UNT Libraries Government Documents Department

Including dislocation flux in a continuum crystal plasticity model to produce size scale effects

Description: A novel model has been developed to capture size scale and gradient effects within the context of continuum crystal plasticity by explicitly incorporating details of dislocation transport, coupling dislocation transport to slip, evolving spatial distributions of dislocations consistent with the flux, and capturing the interactions among various dislocation populations. Dislocation flux and density are treated as nodal degrees of freedom in the finite element model, and they are determined as part of the global system of equations. The creation, annihilation and flux of dislocations between elements are related by transport equations. Crystallographic slip is coupled to the dislocation flux and the stress state. The resultant gradients in dislocation density and local lattice rotations are analyzed for geometrically necessary and statistically stored dislocation contents that contribute to strength and hardening. Grain boundaries are treated as surfaces where dislocation flux is restricted depending on the relative orientations of the neighboring grains. Numerical results show different behavior near free surfaces and non-deforming surfaces resulting from differing levels of dislocation transmission. Simulations also show development of dislocation pile-ups at grain boundaries and an increase in flow strength reminiscent of the Hall-Petch model. The dislocation patterns have a characteristic size independent of the numerical discretization.
Date: February 13, 2004
Creator: Becker, R; Arsenlis, A; Bulatov, V V & Parks, D M
Partner: UNT Libraries Government Documents Department

Laboratory simulation of cometary x rays using a high-resolution microcalorimeter

Description: X-ray emission following charge exchange has been studied on the University of California Lawrence Livermore National Laboratory electron beam ion traps EBIT-I and EBIT-II using a high-resolution microcalorimeter. The measured spectra include the K-shell emission from hydrogen-like and helium-like C, N, O, and Ne needed for simulations of cometary x-ray emission. A comparison of the spectra produced in the interaction of O{sup 8+} with N{sub 2} and CH{sub 4} is presented that illustrates the dependence of the observed spectrum on the interaction gas.
Date: August 13, 2004
Creator: Beiersdorfer, P; Chen, H; Boyce, K R; Brown, G V; Kelley, R L; Kilbourne, C A et al.
Partner: UNT Libraries Government Documents Department

Target Diagnostic Technology Research & Development for the LLNL ICF and HED Program

Description: The National Ignition Facility is operational at LLNL. The ICF and HED programs at LLNL have formed diagnostic research and development groups to institute improvements outside the charter of core diagnostics. We will present data from instrumentation being developed. A major portion of our work is improvements to detectors and readout systems. We have efforts related to CCD device development. Work has been done in collaboration with the University of Arizona to back thin a large format CCD device. We have developed in collaboration with a commercial vendor a large format, compact CCD system. We have coupled large format CCD systems to our optical and x-ray streak cameras leading to improvements in resolution and dynamic range. We will discuss gate-width and uniformity improvements to MCP-based framing cameras. We will present data from single shot data link work and discuss technology aimed at improvements of dynamic range for high-speed transient measurements from remote locations.
Date: April 13, 2004
Creator: Bell, P; Landen, O; Weber, F; Lowry, M; Bennett, C; Kimbrough, J et al.
Partner: UNT Libraries Government Documents Department

The BDGP gene disruption project: Single transposon insertions associated with 40 percent of Drosophila genes

Description: The Berkeley Drosophila Genome Project (BDGP) strives to disrupt each Drosophila gene by the insertion of a single transposable element. As part of this effort, transposons in more than 30,000 fly strains were localized and analyzed relative to predicted Drosophila gene structures. Approximately 6,300 lines that maximize genomic coverage were selected to be sent to the Bloomington Stock Center for public distribution, bringing the size of the BDGP gene disruption collection to 7,140 lines. It now includes individual lines predicted to disrupt 5,362 of the 13,666 currently annotated Drosophila genes (39 percent). Other lines contain an insertion at least 2 kb from others in the collection and likely mutate additional incompletely annotated or uncharacterized genes and chromosomal regulatory elements. The remaining strains contain insertions likely to disrupt alternative gene promoters or to allow gene mis-expression. The expanded BDGP gene disruption collection provides a public resource that will facilitate the application of Drosophila genetics to diverse biological problems. Finally, the project reveals new insight into how transposons interact with a eukaryotic genome and helps define optimal strategies for using insertional mutagenesis as a genomic tool.
Date: January 13, 2004
Creator: Bellen, Hugo J.; Levis, Robert W.; Liao, Guochun; He, Yuchun; Carlson, Joseph W.; Tsang, Garson et al.
Partner: UNT Libraries Government Documents Department

LLNL Scientists Use NERSC to Advance Global Aerosol Simulations

Description: While ''greenhouse gases'' have been the focus of climate change research for a number of years, DOE's ''Aerosol Initiative'' is now examining how aerosols (small particles of approximately micron size) affect the climate on both a global and regional scale. Scientists in the Atmospheric Science Division at Lawrence Livermore National Laboratory (LLNL) are using NERSC's IBM supercomputer and LLNL's IMPACT (atmospheric chemistry) model to perform simulations showing the historic effects of sulfur aerosols at a finer spatial resolution than ever done before. Simulations were carried out for five decades, from the 1950s through the 1990s. The results clearly show the effects of the changing global pattern of sulfur emissions. Whereas in 1950 the United States emitted 41 percent of the world's sulfur aerosols, this figure had dropped to 15 percent by 1990, due to conservation and anti-pollution policies. By contrast, the fraction of total sulfur emissions of European origin has only dropped by a factor of 2 and the Asian emission fraction jumped six fold during the same time, from 7 percent in 1950 to 44 percent in 1990. Under a special allocation of computing time provided by the Office of Science INCITE (Innovative and Novel Computational Impact on Theory and Experiment) program, Dan Bergmann, working with a team of LLNL scientists including Cathy Chuang, Philip Cameron-Smith, and Bala Govindasamy, was able to carry out a large number of calculations during the past month, making the aerosol project one of the largest users of NERSC resources. The applications ran on 128 and 256 processors. The objective was to assess the effects of anthropogenic (man-made) sulfate aerosols. The IMPACT model calculates the rate at which SO{sub 2} (a gas emitted by industrial activity) is oxidized and forms particles known as sulfate aerosols. These particles have a short lifespan in the atmosphere, ...
Date: October 13, 2004
Creator: Bergmann, D J; Chuang, C & Rotman, D
Partner: UNT Libraries Government Documents Department

Poroelastic fluid effects on shear for rocks with soft anisotropy

Description: A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluid mechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2 x 2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy introduced through the poroelastic coefficients, interacts with the mechanics of the pore fluid and produces shear dependence on fluid properties in the overall poroelastic system. The analysis shows for example that this effect is always present (though sometimes small in magnitude) in the systems studied, and can be quite large (on the order of 10 to 20%) for wave propagation studies in some real granites and sandstones, including Spirit River sandstone and Schuler-Cotton Valley sandstone. Some of the results quoted here are obtained by using a new product formula relating local bulk and uniaxial shear energy to the product of the two eigenvalues that are coupled to the fluid mechanics. This product formula was first derived in prior work, but is given a more intuitive derivation here. The results obtained here are observed to be useful both for explaining difficult to reconcile experimental data, and for benchmarking of poroelastic codes.
Date: April 13, 2004
Creator: Berryman, J G
Partner: UNT Libraries Government Documents Department

Improved Pinhole-Apertured Point-Projection Backlighter Geometry

Description: Pinhole-apertured point-projection x-ray radiography is an important diagnostic technique for obtaining high resolution, high contrast, and large field-of-view images used to diagnose the hydrodynamic evolution of high energy density experiments. In this technique, a pinhole aperture is placed between a laser irradiated foil (x-ray source) and an imaging detector. In this letter, we present an improved backlighter geometry that utilizes a tilted pinhole for debris mitigation and a front-side illuminated backlighter foil for improved photon statistics.
Date: April 13, 2004
Creator: Blue, B; Robey, H F & Hansen, J F
Partner: UNT Libraries Government Documents Department

A Progressive Subdivision Paradigm (PSP)

Description: The increasing rate of growth in size of currently available datasets is a well known issue. The possibility of developing fast and easy to implement frameworks able to visualize at least part of a tera-sized volume is a challenging task. Subdivision methods in recent years have been one of the most successful techniques applied to the multiresolution representation and visualization of surface meshes. Extensions of these techniques to the volumetric case presents positive effects and major challenges mainly concerning the generalization of the combinatorial structure of the refinement procedure and the analysis of the smoothness of the limit mesh. In this paper we address mainly the first part of the problem, presenting a framework that exploits a subdivision scheme suitable for extension to 3D and higher dimensional meshes.
Date: December 13, 2004
Creator: Borgo, R; Scopigno, R; Cignoni, P & Pascucci, V
Partner: UNT Libraries Government Documents Department

Colloquium and Report on Systems Microbiology: Beyond Microbial Genomics

Description: The American Academy of Microbiology convened a colloquium June 4-6, 2004 to confer about the scientific promise of systems microbiology. Participants discussed the power of applying a systems approach to the study of biology and to microbiology in particular, specifics about current research efforts, technical bottlenecks, requirements for data acquisition and maintenance, educational needs, and communication issues surrounding the field. A number of recommendations were made for removing barriers to progress in systems microbiology and for improving opportunities in education and collaboration. Systems biology, as a concept, is not new, but the recent explosion of genomic sequences and related data has revived interest in the field. Systems microbiology, a subset of systems biology, represents a different approach to investigating biological systems. It attempts to examine the emergent properties of microorganisms that arise from the interplay of genes, proteins, other macromolecules, small molecules, organelles, and the environment. It is these interactions, often nonlinear, that lead to the emergent properties of biological systems that are generally not tractable by traditional approaches. As a complement to the long-standing trend toward reductionism, systems microbiology seeks to treat the organism or community as a whole, integrating fundamental biological knowledge with genomics, metabolomics, and other data to create an integrated picture of how a microbial cell or community operates. Systems microbiology promises not only to shed light on the activities of microbes, but will also provide biology the tools and approaches necessary for achieving a better understanding of life and ecosystems. Microorganisms are ideal candidates for systems biology research because they are relatively easy to manipulate and because they play critical roles in health, environment, agriculture, and energy production. Potential applications of systems microbiology research range from improvements in the management of bacterial infections to the development of commercial-scale microbial hydrogen generation. A number of technical ...
Date: December 13, 2004
Creator: Buckley, Merry R.
Partner: UNT Libraries Government Documents Department

Thermal Design and Performance of the Gamma-Ray Spectrometer for the MESSENGER Spacecraft

Description: A gamma-ray spectrometer (GRS) has been built and delivered to the Mercury MESSENGER spacecraft which launched on August 3, 2004, from Cape Canaveral, Florida. The GRS, a part of seven scientific instruments on board MESSENGER, is based on a coaxial high-purity germanium detector. Gamma-ray detectors based on germanium have the advantage of providing excellent energy resolution, which is critical to achieving the science goals of the mission. However, germanium has the disadvantage that it must operate at cryogenic temperatures (typically {approx}80 K). This requirement is easy to satisfy in the laboratory but difficult near Mercury, which has an extremely hot thermal radiation environment. To cool the detector, a Stirling cycle mechanical cooler is employed. In addition, radiation and conduction techniques a are used to reduce the GRS heat load. Before delivering the flight sensor, a complete thermal prototype was built and tested. The results of these test, including thermal design, radiative and conductive heat loads, and cooler performance are described.
Date: October 13, 2004
Creator: Burks, M; Cork, C P; Eckels, D; Hull, E; Madden, N W; Miller, W et al.
Partner: UNT Libraries Government Documents Department

Raman Spectroscopic Analysis of Biochemical Changes in Individual Triglyceride-Rich Lipoproteins in the Pre- and Postprandial State

Description: Individual triglyceride-rich lipoprotein (TGRL) particles derived from human volunteers are non-destructively analyzed by laser tweezers Raman microspectroscopy and information on their composition and distribution is obtained. The Raman signature of single optically trapped very low-density lipoproteins (VLDL), a subclass of TGRL, which play an important role in cardiovascular disease, exhibits distinct peaks associated with molecular vibrations of fatty acids, proteins, lipids, and structural rearrangements of lipids. Our analysis of pre- and postprandial VLDL exhibits the signature of biochemical changes in individual lipoprotein particles following the consumption of meals. Interaction of VLDL with endothelium leads to the breakdown of complex triacylglycerols and the formation of a highly ordered core of free saturated fatty acids in the particle. A particle distribution analysis reveals trends in the degree to which this process has occurred in particles at different times during the postprandial period. Differences in particle distributions based on the different ratios of polyunsaturated to saturated fats in the consumed meals are also easily discerned. Individual lipoprotein particles hydrolyzed in-vitro through addition of lipoprotein lipase (LpL) exhibit strikingly similar changes in their Raman spectra. These results demonstrate the feasibility of monitoring the dynamics of lipid metabolism of individual TGRL particles as they interact with LpL in the endothelial cell wall using Raman spectroscopy.
Date: September 13, 2004
Creator: Chan, J; Motton, D; Rutledge, J; Keim, N & Huser, T
Partner: UNT Libraries Government Documents Department

Report on the Instrument Development Workshop for Biological Imaging Experiments at LCLS

Description: The Linac Coherent Light Source (LCLS) will launch a new era in X-ray science by providing 200 fs pulses of X rays with a peak brightness up to 10 orders of magnitude greater than current sources. One of the most exciting and far-reaching experiments that this new source will enable is single-particle diffraction imaging, whereby atomic-resolution structure of biological macromolecules, complexes, or viruses could be obtained without the need for crystallization. Time-resolved structures and dynamic processes could be studied, with time steps as short as the LCLS pulse duration. Many of the components of a diffraction imaging experiment have been demonstrated individually, such as image reconstruction and electrospray mass-spectrometer particle selection. There are many issues that cannot be resolved until bright pulsed X-ray sources become available in 2005 to test theories. Bringing all the techniques together to field an experiment at LCLS in 2009 is a challenging, but quite feasible, undertaking that requires a coordinated and sustained effort of the community.
Date: August 13, 2004
Creator: Chapman, H; Hajdu, J & Hodgson, K
Partner: UNT Libraries Government Documents Department

Evaluation of Glass From The DWPF Melter

Description: The Defense Waste Processing Facility (DWPF) melter has operated for over eight years with more than six years of radioactive operations. For each sludge batch of waste processed a sample of the radioactive glass is analyzed. In conjunction with the pour stream sampling of Sludge Batch 2, a sample of the glass in contact with the pour spout insert was also collected for analysis. The samples were evaluated for chemical composition, crystal content and redox.
Date: February 13, 2004
Creator: Cozzi, AD
Partner: UNT Libraries Government Documents Department

A New Method for Estimating Neutron Reaction Cross Sections Based on Wick's Limit

Description: Wick's limit is an inequality that relates the zero-degree differential elastic scattering cross section to the total cross section. The deviation of Wick's limit from an exact equality is small over a wide range of incident energies and target masses. Under these circumstances we show that Wick's limit can be used to correlate the uncertainties in the two terms of the reaction (nonelastic) cross section expressed as the difference between the total and angle-integrated elastic cross sections. When suitable elastic angular distributions are available, we show that the reaction cross section may be obtained with small errors (typically 1.5-3%). Examples are shown for {sup 208P}b, {sup 54-56}Fe, {sup 232}Th, and {sup 238}U.
Date: October 13, 2004
Creator: Dietrich, F S; Anderson, J D; Bauer, R W & Grimes, S M
Partner: UNT Libraries Government Documents Department

Surrogate Nuclear Reactions and the Origin of the Heavy Elements

Description: An innovative method for indirectly determining reaction cross sections via Surrogate Nuclear Reactions is presented. Exploring indirect approaches for obtaining reaction cross sections is important since a large number of nuclear reactions relevant to astrophysics cannot be measured with currently available techniques. A program is outlined for developing a comprehensive framework for planning and interpreting experiments that can yield the cross sections of interest. The applications will focus on reactions involving unstable nuclei that play a key role in the production of the elements between iron and uranium.
Date: July 13, 2004
Creator: Escher, J; Ahle, L; Bernstein, L; Church, J; Dietrich, F; Forssen, C et al.
Partner: UNT Libraries Government Documents Department

Structure, Stability and ELM Dynamics of the H-Mode Pedestal in DIII-D

Description: Experiments are described that have increased understanding of the transport and stability physics that set the H-mode edge pedestal width and height, determine the onset of Type-I edge localized modes (ELMs), and produce the nonlinear dynamics of the ELM perturbation in the pedestal and scrape-off layer (SOL). Predictive models now exist for the n{sub e} pedestal profile and the p{sub e} height at the onset of Type-I ELMs, and progress has been made toward predictive models of the T{sub e} pedestal width and nonlinear ELM evolution. Similarity experiments between DIII-D and JET suggested that neutral penetration physics dominates in the relationship between the width and height of the n{sub e} pedestal while plasma physics dominates in setting the T{sub e} pedestal width. Measured pedestal conditions including edge current at ELM onset agree with intermediate-n peeling-ballooning (P-B) stability predictions. Midplane ELM dynamics data show the predicted (P-B) structure at ELM onset, large rapid variations of the SOL parameters, and fast radial propagation in later phases, similar to features in nonlinear ELM simulations.
Date: October 13, 2004
Creator: Fenstermacher, M E; Leonard, A W; Osborne, T H; Snyder, P B; Thomas, D M; Boedo, J A et al.
Partner: UNT Libraries Government Documents Department

Monolithic Nickel (II) Oxide Aerogels Using an Organic Epoxide: The Importance of the Counter Ion

Description: The synthesis and characterization of nickel (II) oxide aerogel materials prepared using the epoxide addition method is described. The addition of the organic epoxide propylene oxide to an ethanolic solution of NiCl{sub 2} 6H{sub 2}O resulted in the formation of an opaque light green monolithic gel and subsequent drying with supercritical CO{sub 2} gave a monolithic aerogel material of the same color. This material has been characterized using powder X-ray diffraction, electron microscopy, elemental analysis, and nitrogen adsorption/desorption analysis. The results indicate that the nickel (II) oxide aerogel has very low bulk density (98 kg/m{sup 3} ({approx}98 %porous)), high surface area (413 m{sup 2}/g), and has a particulate-type aerogel microstructure made up of very fine spherical particles with an open porous network. By comparison, a precipitate of Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} is obtained when the same preparation is attempted with the common Ni(NO{sub 3}){sub 2} 6H{sub 2}O salt as the precursor. The implications of the difference of reactivity of the two different precursors are discussed in the context of the mechanism of gel formation via the epoxide addition method. The synthesis of nickel (II) oxide aerogel, using the epoxide addition method, is especially unique in our experience. It is our first example of the successful preparation of a metal oxide aerogel using a metal divalent metal ion and may have implications for the application of this method to the preparation of aerogels or nanoparticles of other divalent metal oxides. To our knowledge this is the first report of a monolithic pure nickel (II) oxide aerogel materials.
Date: January 13, 2004
Creator: Gash, A E; Satcher, J H & Simpson, R L
Partner: UNT Libraries Government Documents Department

Multi Dimensional Phase Only Filter

Description: Today's sensor networks provide a wide variety of application domain for high-speed pattern classification systems. Such high-speed systems can be achieved by the use of optical implementation of specialized POF correlator. In this research we discuss the modeling and simulation of the phase only filter (POF) in the task of pattern classification of multi-dimensional data.
Date: July 13, 2004
Creator: Gudmundsson, K & Awwal, A
Partner: UNT Libraries Government Documents Department

Line-Based Object Recognition using Hausdorff Distance: From Range Images to Molecular Secondary Structure

Description: Object recognition algorithms are fundamental tools in automatic matching of geometric shapes within a background scene. Many approaches have been proposed in the past to solve the object recognition problem. Two of the key aspects that distinguish them in terms of their practical usability are: (i) the type of input model description and (ii) the comparison criteria used. In this paper we introduce a novel scheme for 3D object recognition based on line segment representation of the input shapes and comparison using the Hausdor distance. This choice of model representation provides the flexibility to apply the scheme in different application areas. We define several variants of the Hausdor distance to compare the models within the framework of well defined metric spaces. We present a matching algorithm that efficiently finds a pattern in a 3D scene. The algorithm approximates a minimization procedure of the Hausdor distance. The output error due to the approximation is guaranteed to be within a known constant bound. Practical results are presented for two classes of objects: (i) polyhedral shapes extracted from segmented range images and (ii) secondary structures of large molecules. In both cases the use of our approximate algorithm allows to match correctly the pattern in the background while achieving the efficiency necessary for practical use of the scheme. In particular the performance is improved substantially with minor degradation of the quality of the matching.
Date: December 13, 2004
Creator: Guerra, C & Pascucci, V
Partner: UNT Libraries Government Documents Department