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Quantifying the Contribution of Lubrication Oil to Particulate Emissions from a Diesel Engine
The contribution of lubrication oil to particulate matter (PM) emissions from a Cummins B5.9 Diesel engine was measured using accelerator mass spectrometry to trace carbon isotope concentrations. The engine operated at fixed medium load (285 N-m (210 ft.lbs.) 1600 m) used 100% biodiesel fuel (B100) with a contemporary carbon-14 ({sup 14}C) concentration of 103 amol {sup 14}C/ mg C. The C concentration of the exhaust C02 and PM were 102 and 99 amol {sup 14}C/mg C, respectively. The decrease in I4C content in the PM is due to the consumption of lubrication oil which is {sup 14}C-free. Approximately 4% of the carbon in PM came from lubrication oil under these operating conditions. The slight depression in CO{sub 2} isotope content could be attributed to ambient CO{sub 2} levels and measurement uncertainty.
Date:
December 6, 2002
Creator:
Cheng, A. S.; Rich, D.; Dibble, R. W. & Buchholz, B. A.
Object Type:
Article
System:
The UNT Digital Library
Practical Issues Associated with Mortar Projections in Large Deformation Contact/Impact Analysis
Several recent works have considered variants of the mortar-finite element method for numerical treatment of contact phenomena. The method has shown considerable promise for the spatial discretization of contact interactions, particularly for kinematically linear applications where one or both of the contacting surfaces are flat. Desirable features already demonstrated for the method in this specialized setting include passage of patch tests, preservation of convergence rates that would be obtained with a perfectly conforming mesh, and accurate resolution of contact stresses on interfaces. This paper concerns itself with the successful extension of these methods to encompass contact of geometrically noncoincident surfaces. The issue of patch test passage over curved interfaces will be discussed. It will be shown that a generalization of the mortar projection method is required to pass patch tests in this instance. Issues relating to the exact numerical integration of the mortar projection integrals will also be outlined, and a convergence study for a mortar tying application will be presented.
Date:
May 2, 2002
Creator:
Laursen, T. A.; Puso, M. A. & Heinstein, M. W.
Object Type:
Article
System:
The UNT Digital Library
National Ignition Facility Configuration Management Plan
This Configuration Management Plan (CMP) describes the technical and administrative management process for controlling the National Ignition Facility (NIF) Project configuration. The complexity of the NIF Project (i.e., participation by multiple national laboratories and subcontractors involved in the development, fabrication, installation, and testing of NIF hardware and software, as well as construction and testing of Project facilities) requires implementation of the comprehensive configuration management program defined in this plan. A logical schematic illustrating how the plan functions is provided in Figure 1. A summary of the process is provided in Section 4.0, Configuration Change Control. Detailed procedures that make up the overall process are referenced. This CMP is consistent with guidance for managing a project's configuration provided in Department of Energy (DOE) Order 430.1, Guide PMG 10, ''Project Execution and Engineering Management Planning''. Configuration management is a formal discipline comprised of the following four elements: (1) Identification--defines the functional and physical characteristics of a Project and uniquely identifies the defining requirements. This includes selection of components of the end product(s) subject to control and selection of the documents that define the project and components. (2) Change management--provides a systematic method for managing changes to the project and its physical and …
Date:
October 1, 2002
Creator:
Cabral, S. G. & Moore, T. L.
Object Type:
Report
System:
The UNT Digital Library
The National Ignition Facility: Status and Plans for Laser Fusion and High-Energy-Density Experimental Studies
The National Ignition Facility (NIF), currently under construction at the University of California's Lawrence Livermore National Laboratory is a $2.25B stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, 351-nm laser system. NIF is being built by the National Nuclear Security Agency and when completed will be the world's largest laser system, providing a national center to study inertial confinement fusion and the physics of extreme energy densities and pressures. In NIF up to 192 energetic laser beams will compress small fusion targets to conditions where they will ignite and burn, liberating more energy than is required to initiate the fusion reactions. NIF experiments will allow the study of physical processes at temperatures approaching 100 million K and 100 billion times atmospheric pressure. These conditions exist naturally only in the interior of stars and in nuclear weapons explosions. In the course of designing the world's most energetic laser system, a number of significant technology breakthroughs have been achieved. Research is also underway to develop a shorter pulse capability on NIF for high power applications. We discuss here the technology challenges and solutions that have made NIF possible along with enhancements to NIF's design that could lead to exawatt power levels.
Date:
January 11, 2002
Creator:
Moses, E I
Object Type:
Article
System:
The UNT Digital Library
Non-Equilibrium Zeldovich-Von Neumann-Doring Theory and Reactive Flow Modeling of Detonation
This paper discusses the Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation waves and the Ignition and Growth reactive flow model of shock initiation and detonation wave propagation in solid explosives. The NEZND theory identified the non-equilibrium excitation processes that precede and follow the exothermic decomposition of a large high explosive molecule into several small reaction product molecules. The thermal energy deposited by the leading shock wave must be distributed to the vibrational modes of the explosive molecule before chemical reactions can occur. The induction time for the onset of the initial endothermic reactions can be calculated using high pressure, high temperature transition state theory. Since the chemical energy is released well behind the leading shock front of a detonation wave, a physical mechanism is required for this chemical energy to reinforce the leading shock front and maintain its overall constant velocity. This mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure of detonation waves observed for all explosives. For practical predictions of shock initiation and detonation in hydrodynamic codes, …
Date:
May 2, 2002
Creator:
Tarver, C M; Forbes, J W & Urtiew, P A
Object Type:
Article
System:
The UNT Digital Library
A SPICE Model and Electrostatic Field Analysis of the MOS Turn-Off Thyristor
This paper presents a circuit model and an electrostatic field analysis with an approximate model of the SDM170HK MOS turn-off thyristor (MTO) fabricated by Silicon Power Corporation. The circuit model consists of five cells, each containing two bipolar junction transistors and three resistors. The turn-off feature of the MTO was simulated by inserting an array of 21 Fairchild FDS6670A MOSFET importable sub-circuit components between the cathode and the turn-on gate. The model was then used to create a four-terminal sub-circuit component representing the MTO that can be readily imported into computer-aided circuit design programs such as PSPICE and Micro-Cap. The generated static I-V characteristics and simulated switching waveforms are shown. The electrostatic field analysis was done for the maximum operating voltage of 4.5 kV using the Ansoft Maxwell 3D field simulator. Electrostatic field magnitudes that exceed the nominal air breakdown threshold of 30 kV/cm were observed surrounding the simulated turn-off gate wire, the turn-off gate ring contact, and the cathode ring contact. The resulting areas of high fields are a concern, as arc track marks have been found on the inner surface of the ceramic insulator near the internal gate connections of a failed device.
Date:
August 5, 2002
Creator:
Kelly, D. Q.; Mayhall, D. J.; Wilson, M. J. & Lahowe, D. A.
Object Type:
Report
System:
The UNT Digital Library
Unstructured Mesh Connectivity in Unstructured Mapping
The connectivity interface for UnstructuredMapping has been rewritten to provide a more thorough interface to the mesh. This new design also resembles the TSTT mesh query interface. While data is still stored in array form, indexed by integers, the interface provides iterators through the mesh entities and adjacencies. This document describes the additions to the UnstructuredMapping class as well as the definition and use of the UnstructuredMappingIterator and UnstructuredMappingAdjacencyIterator classes.
Date:
October 22, 2002
Creator:
Chand, K
Object Type:
Text
System:
The UNT Digital Library
Materials Properties Database for Selection of High-Temperature Alloys and Concepts of Alloy Design for SOFC Applications
To serve as an interconnect / gas separator in an SOFC stack, an alloy should demonstrate the ability to provide (i) bulk and surface stability against oxidation and corrosion during prolonged exposure to the fuel cell environment, (ii) thermal expansion compatibility with the other stack components, (iii) chemical compatibility with adjacent stack components, (iv) high electrical conductivity of the surface reaction products, (v) mechanical reliability and durability at cell exposure conditions, (vii) good manufacturability, processability and fabricability, and (viii) cost effectiveness. As the first step of this approach, a composition and property database was compiled for high temperature alloys in order to assist in determining which alloys offer the most promise for SOFC interconnect applications in terms of oxidation and corrosion resistance. The high temperature alloys of interest included Ni-, Fe-, Co-base superal
Date:
November 24, 2002
Creator:
Yang, Z Gary; Paxton, Dean M.; Weil, K. Scott; Stevenson, Jeffry W. & Singh, Prabhakar
Object Type:
Report
System:
The UNT Digital Library
Comparison Between Keyhole Weld Model and Laser Welding Experiments
A series of laser welds were performed using a high-power diode-pumped continuous-wave Nd:YAG laser welder. In a previous study, the experimental results of those welds were examined, and the effects that changes in incident power and various welding parameters had on weld geometry were investigated. In this report, the fusion zones of the laser welds are compared with those predicted from a laser keyhole weld simulation model for stainless steels (304L and 21-6-9), vanadium, and tantalum. The calculated keyhole depths for the vanadium and 304L stainless steel samples fit the experimental data to within acceptable error, demonstrating the predictive power of numerical simulation for welds in these two materials. Calculations for the tantalum and 21-6-9 stainless steel were a poorer match to the experimental values. Accuracy in materials properties proved extremely important in predicting weld behavior, as minor changes in certain properties had a significant effect on calculated keyhole depth. For each of the materials tested, the correlation between simulated and experimental keyhole depths deviated as the laser power was increased. Using the model as a simulation tool, we conclude that the optical absorptivity of the material is the most influential factor in determining the keyhole depth. Future work will …
Date:
September 23, 2002
Creator:
Wood, B C; Palmer, T A & Elmer, J W
Object Type:
Report
System:
The UNT Digital Library
Characterization of Vadose Zone Sediment: Borehole C3103 Located in the 216-B-7A Crib Near the B Tank Farm
This report summarizes data collected from samples in borehole C3103. Borehole C3103 was completed to further characterize the nature and extent of vadose zone contaminants supplied by intentional liquid discharges into the crib 216-B7A/7B between 1954 and 1967. These cribs received dilute waste streams from the bismuth phosphate fuel reprocessing program in the 1950's and decontamination waste in the 1960's. Elevated concentrations of several constituents were primarily measured at different depth intervals. The primary radionuclides present in this borehole are cesium-137 and uranium near the top of the borehole. Chemical characteristics attributed to wastewater-soil interaction at different locations within this zone are elevated pH, sodium, fluoride, carbonate nitrate, and sulphate
Date:
December 1, 2002
Creator:
Lindenmeier, Clark W.; Serne, R JEFFREY.; Bjornstad, Bruce N.; Last, George V.; Lanigan, David C.; Lindberg, Michael J. et al.
Object Type:
Report
System:
The UNT Digital Library
Hybrid Heat Capacity - Moving Slab Laser Concept
A hybrid configuration of a heat capacity laser (HCL) and a moving slab laser (MSL) has been studied. Multiple volumes of solid-state laser material are sequentially diode-pumped and their energy extracted. When a volume reaches a maximum temperature after a ''sub-magazine depth'', it is moved out of the pumping region into a cooling region, and a new volume is introduced. The total magazine depth equals the submagazine depth times the number of volumes. The design parameters are chosen to provide high duty factor operation, resulting in effective use of the diode arrays. The concept significantly reduces diode array cost over conventional heat capacity lasers, and it is considered enabling for many potential applications. A conceptual design study of the hybrid configuration has been carried out. Three concepts were evaluated using CAD tools. The concepts are described and their relative merits discussed. Because of reduced disk size and diode cost, the hybrid concept may allow scaling to average powers on the order of 0.5 MW/module.
Date:
April 1, 2002
Creator:
Stappaerts, E A
Object Type:
Report
System:
The UNT Digital Library
Horizontal and Slant-Path Surveillance with Speckle Imaging
A fundamental problem in providing high-quality surveillance images recorded over long horizontal or slant paths is the blurring caused by atmospheric turbulence, which reduces both the resolution and contrast. The objective of the work reported here is to develop a capability for long-range imaging through the atmosphere that is not limited by the atmosphere but only by the fundamental diffraction limit of the optics. This paper describes our recent horizontal and slant-path imaging experiments of point targets and extended scenes as well as simulations of point targets in comparison to experiment. We show the near-diffraction limited resolution results obtained using bispectral speckle-imaging techniques. The experiments were performed with an 8-inch diameter telescope placed either in a field, on a rooftop, or on a hillside and cover ranges of interest from 100 meters up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures.
Date:
August 19, 2002
Creator:
Carrano, C J & Brase, J M
Object Type:
Article
System:
The UNT Digital Library
Electronic Structure and Doping of P-Type Transparent Conducting Oxides: Preprint
Transparent conducting oxides (TCOs) are a group of materials that are widely used in solar cells and other optoelectronic devices. Recently, Cu-containing p-type TCOs such as MII Cu2 O2 (MIII=Mg, Ca, Sr, Ba) and CuMIII O2 (MIII=Al, Ga, In) have been proposed. Using first-principles band structure methods, we have systematically studied the electronic and optical properties of these p-type transparent oxides. For MII Cu2 O2 , we predict that adding a small amount of Ca into Sr Cu2 O2 can increase the transparency and conductivity. For CuMIII O2 , we explained the doping and band gap anomalies in this system and proposed a new approach to search for bipolar dopable wide-gap materials.
Date:
May 1, 2002
Creator:
Wei, S.-H.; Nie, X. & Zhang, S. B.
Object Type:
Article
System:
The UNT Digital Library
A Parallel Multigrid Method for the Finite Element Analysis of Mechanical Contact
A geometrical multigrid method for solving the linearized matrix equations arising from node-on-face three-dimensional finite element contact is described. The development of an efficient implementation of this combination that minimizes both the memory requirements and the computational cost requires careful construction and storage of the portion of the coarse mesh stiffness matrices that are associated with the contact stiffness on the fine mesh. The multigrid contact algorithm is parallelized in a manner suitable for distributed memory architectures: results are presented that demonstrates the scheme's scalability. The solution of a large contact problem derived from an analysis of the factory joints present in the Space Shuttle reusable solid rocket motor demonstrates the usefulness of the general approach.
Date:
March 21, 2002
Creator:
Hales, J. D. & Parsons, I. D.
Object Type:
Report
System:
The UNT Digital Library
20% Partial Siberian Snake in the AGS.
An 11.4% partial Siberian snake was used to successfully accelerate polarized proton through a strong intrinsic depolarizing spin resonance in the AGS. No noticeable depolarization was observed. This opens up the possibility of using a 20% to 30% partial Siberian snake in the AGS to overcome all weak and strong depolarizing spin resonances. Some design and operation issues of the new partial Siberian snake are discussed.
Date:
November 6, 2002
Creator:
Huang, H.; Bai, M.; Brown, K. A.; Glenn, W.; Luccio, A. U.; MacKay, W. W. et al.
Object Type:
Article
System:
The UNT Digital Library
Ultrasound Imaging Using Diffraction Tomography in a Cylindrical Geometry
Tomographic images of tissue phantoms and a sample of breast tissue have been produced from an acoustic synthetic array system for frequencies near 500 kHz. The images for sound speed and attenuation show millimeter resolution and demonstrate the feasibility of obtaining high-resolution tomographic images with frequencies that can deeply penetrate tissue. The image reconstruction method is based on the Born approximation to acoustic scattering and is a simplified version of a method previously used by Andre (Andre, et. al., Int. J. Imaging Systems and Technology, Vol 8, No. 1, 1997) for a circular acoustic array system. The images have comparable resolution to conventional ultrasound images at much higher frequencies (3-5 MHz) but with lower speckle noise. This shows the potential of low frequency, deeply penetrating, ultrasound for high-resolution quantitative imaging.
Date:
January 24, 2002
Creator:
Chambers, D H & Littrup, P
Object Type:
Article
System:
The UNT Digital Library
A Dynamically Adaptive Arbitrary Lagrangian-Eulerian Method for Hydrodynamics
A new method that combines staggered grid Arbitrary Lagrangian-Eulerian (ALE) techniques with structured local adaptive mesh refinement (AMR) has been developed for solution of the Euler equations. The novel components of the combined ALE-AMR method hinge upon the integration of traditional AMR techniques with both staggered grid Lagrangian operators as well as elliptic relaxation operators on moving, deforming mesh hierarchies. Numerical examples demonstrate the utility of the method in performing detailed three-dimensional shock-driven instability calculations.
Date:
October 19, 2002
Creator:
Anderson, R W; Pember, R B & Elliott, N S
Object Type:
Article
System:
The UNT Digital Library
Structured Extended Finite Element Methods of Solids Defined by Implicit Surfaces
A paradigm is developed for generating structured finite element models from solid models by means of implicit surface definitions. The implicit surfaces are defined by radial basis functions. Internal features, such as material interfaces, sliding interfaces and cracks are treated by enrichment techniques developed in the extended finite element method (X-FEM). Methods for integrating the weak form for such models are proposed. These methods simplify the generation of finite element models. Results presented for several examples show that the accuracy of this method is comparable to standard unstructured finite element methods.
Date:
November 17, 2002
Creator:
Belytschko, T; Mish, K; Moes, N & Parimi, C
Object Type:
Report
System:
The UNT Digital Library
Statistical Stability and Time-Reversal Imgaing in Random Media
Localization of targets imbedded in a heterogeneous background medium is a common problem in seismic, ultrasonic, and electromagnetic imaging problems. The best imaging techniques make direct use of the eigenfunctions and eigenvalues of the array response matrix, as recent work on time-reversal acoustics has shown. Of the various imaging functionals studied, one that is representative of a preferred class is a time-domain generalization of MUSIC (MUltiple Signal Classification), which is a well-known linear subspace method normally applied only in the frequency domain. Since statistical stability is not characteristic of the frequency domain, a transform back to the time domain after first diagonalizing the array data in the frequency domain takes optimum advantage of both the time-domain stability and the frequency-domain orthogonality of the relevant eigenfunctions.
Date:
February 5, 2002
Creator:
Berryman, J; Borcea, L; Papanicolaou, G & Tsogka, C
Object Type:
Article
System:
The UNT Digital Library
Hierarchical Volume Representation with 3{radical}2 Subdivision and Trivariate B-Spline Wavelets
Multiresolution methods provide a means for representing data at multiple levels of detail. They are typically based on a hierarchical data organization scheme and update rules needed for data value computation. We use a data organization that is based on what we call n{radical}2 subdivision. The main advantage of subdivision, compared to quadtree (n = 2) or octree (n = 3) organizations, is that the number of vertices is only doubled in each subdivision step instead of multiplied by a factor of four or eight, respectively. To update data values we use n-variate B-spline wavelets, which yields better approximations for each level of detail. We develop a lifting scheme for n = 2 and n = 3 based on the n{radical}2-subdivision scheme. We obtain narrow masks that could also provide a basis for view-dependent visualization and adaptive refinement.
Date:
January 11, 2002
Creator:
Linsen, L; Gray, JT; Pascucci, V; Duchaineau, M & Hamann, B
Object Type:
Article
System:
The UNT Digital Library
A study on D0 Run2b stave structural performance
Two different structural solutions have been proposed and studied for the D0 Run2b stave (Figure 1 and Figure 3). The way the stave structural stiffness is achieved in both designs is essentially the same: the structural material is displaced as far as possible from the neutral axis in order to increase the bending moment of the stave. The agreement of the measured data with what has been theoretically predicted is excellent. The C channel stave with dog-bones glued on top of the sensor (stave No.2) has outperformed the other mockups with a predicted sag of 51 {micro}m for a distributed load of 2.28 N/m [0.013 lbf/in] and a consequent natural frequency of 89.2Hz. The other three C channel staves with the dog-bones not glued on the sensor have a bending stiffness that is -19.0%, -10.8%, +4.0% of that of stave No.2, being 11.0%, 7.8%, 15.1% lighter respectively. An optimized stave structural proposal with 130.5% of the design stiffness within the mass budget is presented at the end of this paper.
Date:
April 1, 2002
Creator:
Lanfranco, Giobatta
Object Type:
Report
System:
The UNT Digital Library
Contribution of Neutron Beta Decay to Radiation Belt Pumping from High Altitude Nuclear Explosion
In 1962, several satellites were lost following high altitude nuclear tests by the United States and the Soviet Union. These satellite failures were caused by energetic electrons injected into the earth's radiation belts from the beta decay of bomb produced fission fragments and neutrons. It has been 40 years since the last high altitude nuclear test; there are now many more satellites in orbit, and it is important to understand their vulnerability to radiation belt pumping from nuclear explosions at high altitude or in space. This report presents the results of a calculation of the contribution of neutron beta decay to artificial belt pumping. For most high altitude nuclear explosions, neutrons are expected to make a smaller contribution than fission products to the total trapped electron inventory, and their contribution is usually neglected. However, the neutron contribution may dominate in cases where the fission product contribution is suppressed due to the altitude or geomagnetic latitude of the nuclear explosion, and for regions of the radiation belts with field lines far from the detonation point. In any case, an accurate model of belt pumping from high altitude nuclear explosions, and a self-consistent explanation of the 1962 data, require inclusion of the …
Date:
November 13, 2002
Creator:
Marrs, R
Object Type:
Report
System:
The UNT Digital Library
Time Reversal Signal Processing in Communications - A Feasibility Study
A typical communications channel is subjected to a variety of signal distortions, including multipath, that corrupt the information being transmitted and reduce the effective channel capacity. The mitigation of the multipath interference component is an ongoing concern for communication systems operating in complex environments such as might be experienced inside buildings, urban environments, and hilly or heavily wooded areas. Communications between mobile units and distributed sensors, so important to national security, are dependent upon flawless conveyance of information in complex environments. The reduction of this multipath corruption necessitates better channel equalization, i.e., the removal of channel distortion to extract the transmitted information. But, the current state of the art in channel equalization either requires a priori knowledge of the channel or the use of a known training sequence and adaptive filtering. If the ''assumed'' model within the equalization processor does not at least capture the dominant characteristics of the channel, then the received information may still be highly distorted and possibly useless. Also, the processing required for classical equalization is demanding in computational resources. To remedy this situation, many techniques have been investigated to replace classical equalization. Such a technique, the subject of this feasibility study, is Time Reversal Signal …
Date:
January 30, 2002
Creator:
Meyer, A W; Candy, J V & Poggio, A J
Object Type:
Report
System:
The UNT Digital Library
The Multi-Scale Model Approach to Thermohydrology at Yucca Mountain
The Multi-Scale Thermo-Hydrologic (MSTH) process model is a modeling abstraction of them1 hydrology (TH) of the potential Yucca Mountain repository at multiple spatial scales. The MSTH model as described herein was used for the Supplemental Science and Performance Analyses (BSC, 2001) and is documented in detail in CRWMS M&O (2000) and Glascoe et al. (2002). The model has been validated to a nested grid model in Buscheck et al. (In Review). The MSTH approach is necessary for modeling thermal hydrology at Yucca Mountain for two reasons: (1) varying levels of detail are necessary at different spatial scales to capture important TH processes and (2) a fully-coupled TH model of the repository which includes the necessary spatial detail is computationally prohibitive. The MSTH model consists of six ''submodels'' which are combined in a manner to reduce the complexity of modeling where appropriate. The coupling of these models allows for appropriate consideration of mountain-scale thermal hydrology along with the thermal hydrology of drift-scale discrete waste packages of varying heat load. Two stages are involved in the MSTH approach, first, the execution of submodels, and second, the assembly of submodels using the Multi-scale Thermohydrology Abstraction Code (MSTHAC). MSTHAC assembles the submodels in a …
Date:
March 27, 2002
Creator:
Glascoe, L.; Buscheck, T. A.; Gansemer, J. & Sun, Y.
Object Type:
Report
System:
The UNT Digital Library