Spatial Analysis of Emissions Sources for HCCI Combustion at Low Loads Using a Multi-Zone Model (open access)

Spatial Analysis of Emissions Sources for HCCI Combustion at Low Loads Using a Multi-Zone Model

We have conducted a detailed numerical analysis of HCCI engine operation at low loads to investigate the sources of HC and CO emissions and the associated combustion inefficiencies. Engine performance and emissions are evaluated as fueling is reduced from typical HCCI conditions, with an equivalence ratio f = 0.26 to very low loads (f = 0.04). Calculations are conducted using a segregated multi-zone methodology and a detailed chemical kinetic mechanism for iso-octane with 859 chemical species. The computational results agree very well with recent experimental results. Pressure traces, heat release rates, burn duration, combustion efficiency and emissions of hydrocarbon, oxygenated hydrocarbon, and carbon monoxide are generally well predicted for the whole range of equivalence ratios. The computational model also shows where the pollutants originate within the combustion chamber, thereby explaining the changes in the HC and CO emissions as a function of equivalence ratio. The results of this paper contribute to the understanding of the high emission behavior of HCCI engines at low equivalence ratios and are important for characterizing this previously little explored, yet important range of operation.
Date: February 20, 2004
Creator: Aceves, S. M.; Flowers, D. L.; Espinosa-Loza, F.; Martinez-Frias, J.; Dec, J. E.; Sjoberg, M. et al.
Object Type: Article
System: The UNT Digital Library
Public Aid and Faith-Based Organizations (Charitable Choice): Background and Selected Legal Issues (open access)

Public Aid and Faith-Based Organizations (Charitable Choice): Background and Selected Legal Issues

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Date: February 20, 2002
Creator: Ackerman, David M.
Object Type: Report
System: The UNT Digital Library
The {phi} mean free path in hot hadronic matter (open access)

The {phi} mean free path in hot hadronic matter

We calculate the {phi} meson collision rate and mean free path in a hot hadronic gas. The Hidden Local Symmetry model is used to take into account interactions of {phi} mesons with pseudoscalar ({pi}, K) and vector mesons ({rho}, {omega}, K*, {phi}). In contrast to previous calculations we find a significantly small mean free path (around 1 fm at T=200MeV). This implies that {phi} mesons produced after hadronization in relativistic heavy ion collisions will not leave the collision region without scattering. The consequences of these findings to the analysis of {phi} yields are discussed.
Date: February 20, 2002
Creator: Alvarez-Ruso, Luis & Koch, Volker
Object Type: Article
System: The UNT Digital Library
Phi meson propagation in a hot hadronic gas (open access)

Phi meson propagation in a hot hadronic gas

The Hidden Local Symmetry Lagrangian is used to study the interactions of phi mesons with other pseudoscalar and vector mesons in a hadronic gas at finite temperature. We have found a significantly small phi mean free path (less than 2.4 fm at T > 170 MeV) due to large collision rates with rho mesons, kaons and predominantly K* in spite of their heavy mass. This implies that phi mesons produced after hadronization in relativistic heavy ion collisions will not leave the hadronic system without scattering. The effect of these interactions on the time evolution of the phi density in the expanding hadronic fireball is investigated.
Date: February 20, 2002
Creator: Alvarez-Ruso, Luis & Koch, Volker
Object Type: Article
System: The UNT Digital Library
FY 2007 Miniature Spherical Retroreflectors Final Report (open access)

FY 2007 Miniature Spherical Retroreflectors Final Report

Miniature spherical retroreflectors, less than 8 millimeters in diameter, are currently being developed to enhance remote optical detection of nuclear proliferation activities. These retroreflecting spheres resemble small, sand-colored marbles that have the unique optical property of providing a strong reflection directly back to the source (i.e., retroreflecting) when illuminated with a laser. The addition of specific coatings, sensitive to specific chemicals or radioactive decay in the environment, can be applied to the surface of these retroreflectors to provide remote detection of nuclear proliferation activities. The presence of radioactive decay (e.g., alpha, gamma, neutron) or specific chemicals in the environment (e.g., TBP, acids) will change the optical properties of the spheres in a predictable fashion, thus indicating the presence or absence of the target materials. One possible scenario might employ an airborne infrared laser system (e.g., quantum-cascade lasers) to illuminate a section of ground littered with these retroreflective spheres. Depending on the coating and the presence of a specific chemical or radioisotope in the environment, the return signal would be modified in some predictable fashion because of fluorescence, frequency shifting, intensity attenuation/enhancement, or change in polarization. Research conducted in FY 2007 focused on developing novel optical fabrication processes and exploiting the …
Date: February 20, 2008
Creator: Anheier, Norman C.; Bernacki, Bruce E. & Krishnaswami, Kannan
Object Type: Report
System: The UNT Digital Library
Preoperational Subsurface Conditions at the Idaho Nuclear Technology and Engineering Center Service Wastewater Discharge Facility (open access)

Preoperational Subsurface Conditions at the Idaho Nuclear Technology and Engineering Center Service Wastewater Discharge Facility

The Idaho Nuclear Technology and Engineering Center (INTEC) Service Wastewater Discharge Facility replaces the existing percolation ponds as a disposal facility for the INTEC Service Waste Stream. A preferred alternative for helping decrease water content in the subsurface near INTEC, closure of the existing ponds is required by the INTEC Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Record of Decision (ROD) for Waste Area Group 3 Operable Unit 3-13 (DOE-ID 1999a). By August 2002, the replacement facility was constructed approximately 2 miles southwest of INTEC, near the Big Lost River channel. Because groundwater beneath the Idaho National Engineering and Environmental Laboratory (INEEL) is protected under Federal and State of Idaho regulations from degradation due to INEEL activities, preoperational data required by U.S. Department of Energy (DOE) Order 5400.1 were collected. These data include preexisting physical, chemical, and biological conditions that could be affected by the discharge; background levels of radioactive and chemical components; pertinent environmental and ecological parameters; and potential pathways for human exposure or environmental impact. This document presents specific data collected in support of DOE Order 5400.1, including: four quarters of groundwater sampling and analysis of chemical and radiological parameters; general facility description; site specific geology, stratigraphy, …
Date: February 20, 2002
Creator: Ansley, Shannon L.
Object Type: Report
System: The UNT Digital Library
Fabrication of large diameter alumino-silicate K{sup +} sources (open access)

Fabrication of large diameter alumino-silicate K{sup +} sources

Alumino-silicate K{sup +} sources have been used in HIF experiments for many years. For example the Neutralized Transport Expt. (NTX) and the High Current Transport Expt. (HCX) are now using this type of ion source with diameters of 2.54 cm and 10 cm respectively. These sources have demonstrated ion currents of 80 mA and 700 mA, for typical HIF pulse lengths of 5-10 {micro}s. The corresponding current density is {approx} 10-15 mA/cm{sup 2}, but much higher current density has been observed using smaller size sources. Recently we have improved our fabrication techniques and, therefore, are able to reliably produce large diameter ion sources with high quality emitter surface without defects. This note provides a detailed description of the procedures employed in the fabrication process. The variables in the processing steps affecting surface quality, such as substrate porosity, powder size distribution, coating technique on large area concave surfaces, drying, and heat firing temperature have been investigated.
Date: February 20, 2003
Creator: Baca, D.; Chacon-Golcher, E.; Kwan, J. W. & Wu, J. K.
Object Type: Article
System: The UNT Digital Library
The Strategic Petroleum Reserve: History, Perspectives and Issues (open access)

The Strategic Petroleum Reserve: History, Perspectives and Issues

This reports discusses the history and establishment of Strategic Petroleum Reserve (SPR), acquisition of crude oil for the SPR. It talks about the debate over the years regarding when should the SPR be used.
Date: February 20, 2009
Creator: Bamberger, Robert
Object Type: Report
System: The UNT Digital Library
HEAT OF DILUTION CALCULATION FOR 19 MOLAR SODIUM HYDROXIDE WITH WATER FOR USE IN 241-S-112 (open access)

HEAT OF DILUTION CALCULATION FOR 19 MOLAR SODIUM HYDROXIDE WITH WATER FOR USE IN 241-S-112

High concentration caustic solutions are known to cause stress corrosion cracking in carbon steel at elevated temperature. This calculation establishes the conditions where heat of dilution will not cause the solution temperature--concentration to exceed the boundary for stress corrosion cracking as established by NACE International.
Date: February 20, 2007
Creator: Barton, W. B.
Object Type: Report
System: The UNT Digital Library
Farm and Food Support Under USDA's Section 32 Program (open access)

Farm and Food Support Under USDA's Section 32 Program

The 110th Congress in June 2008 passed a new omnibus farm bill (P.L. 110-246). Provisions in this new law now spell out more explicitly how the Secretary is to use the annual Section 32 appropriation. Section 32 of the act of August 24, 1935 (P.L. 74-320 as amended; 7 U.S.C. 612c) authorizes a permanent appropriation equal to 30% of annual U.S. customs receipts.
Date: February 20, 2009
Creator: Becker, Geoffrey S.
Object Type: Report
System: The UNT Digital Library
High-resolution crystal spectrometer for the 10-60 (angstrom) EUV region (open access)

High-resolution crystal spectrometer for the 10-60 (angstrom) EUV region

A vacuum crystal spectrometer with nominal resolving power approaching 1000 is described for measuring emission lines with wavelength in the extreme ultraviolet region up to 60 Angstroms. The instrument utilizes a flat octadecyl hydrogen maleate (OHM) crystal and a thin-window 1-D position-sensitive gas proportional detector. This detector employs a 1 {micro}m-thick 100 x8 mm{sup 2} aluminized polyimide window and operates at one atmosphere pressure. The spectrometer has been implemented on the Livermore electron beam ion traps. The performance of the instrument is illustrated in measurements of the newly discovered magnetic field-sensitive line in Ar{sup 8+}.
Date: February 20, 2004
Creator: Beiersdorfer, P; Brown, G V; Goddard, R & Wargelin, B J
Object Type: Article
System: The UNT Digital Library
Three-Loop Superfiniteness of N=8 Supergravity (open access)

Three-Loop Superfiniteness of N=8 Supergravity

We construct the three-loop four-point amplitude of N = 8 supergravity using the unitarity method. The amplitude is ultraviolet finite in four dimensions. Novel cancellations, not predicted by traditional superspace power-counting arguments, render its degree of divergence in D dimensions to be no worse than that of N = 4 super-Yang-Mills theory--a finite theory in four dimensions. Similar cancellations can be identified at all loop orders in certain unitarity cuts, suggesting that N = 8 supergravity may be a perturbatively finite theory of quantum gravity.
Date: February 20, 2007
Creator: Bern, Z.; Carrasco, J.J.; Dixon, L.J.; Johansson, H.; Kosower, D.A. & Roiban, R.
Object Type: Article
System: The UNT Digital Library
Intelligence Issues for Congress (open access)

Intelligence Issues for Congress

This report discusses intelligence issues for Congress including narcotics trafficking, conflicts between Israel and Palestine, in Iraq, and among the former Yugoslav states, and North Korean missile capabilities. Updated February 20, 2002.
Date: February 20, 2002
Creator: Best, Richard A., Jr.
Object Type: Report
System: The UNT Digital Library
The Physical Renormalization of Quantum Field Theories (open access)

The Physical Renormalization of Quantum Field Theories

The profound revolutions in particle physics likely to emerge from current and future experiments motivates an improved understanding of the precise predictions of the Standard Model and new physics models. Higher order predictions in quantum field theories inevitably requires the renormalization procedure, which makes sensible predictions out of the naively divergent results of perturbation theory. Thus, a robust understanding of renormalization is crucial for identifying and interpreting the possible discovery of new physics. The results of this thesis represent a broad set of investigations in to the nature of renormalization. The author begins by motivating a more physical approach to renormalization based on gauge-invariant Green's functions. The resulting effective charges are first applied to gauge coupling unification. This approach provides an elegant formalism for understanding all threshold corrections, and the gauge couplings unify in a more physical manner compared to the usual methods. Next, the gauge-invariant three-gluon vertex is studied in detail, revealing an interesting and rich structure. The effective coupling for the three-gluon vertex, {alpha}(k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}), depends on three momentum scales and gives rise to an effective scale Q{sub eff}{sup 2}(k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}) which governs the …
Date: February 20, 2007
Creator: Binger, Michael William.
Object Type: Report
System: The UNT Digital Library
Estimating Filtering Errors Using the Peano Kernel Theorem (open access)

Estimating Filtering Errors Using the Peano Kernel Theorem

The Peano Kernel Theorem is introduced and a frequency domain derivation is given. It is demonstrated that the application of this theorem yields simple and accurate formulas for estimating the error introduced into a signal by filtering it to reduce noise.
Date: February 20, 2009
Creator: Blair, Jerome
Object Type: Article
System: The UNT Digital Library
An investigation of the resistance rise and power fade in high-power Li-ion cells. (open access)

An investigation of the resistance rise and power fade in high-power Li-ion cells.

Two different cell chemistries, Gen 1 and Gen 2, were subjected to accelerated aging experiments. In Gen 1 calendar-life experiments, useful cell life was strongly affected by temperature and time. Higher temperatures accelerated the degradation of cell performance. The rates of resistance increase and power fade followed simple laws based on a power of time and Arrhenius kinetics. The data have been modeled using these two concepts, and the calculated data agree well with the experimental values. The Gen 1 calendar-life resistance increase and power fade data follow (time){sup 1/2} kinetics. This may be due to solid electrolyte interface (SEI) layer growth. From the cycle-life experiments, the resistance increase data also follow (time){sup 1/2} kinetics. But there is an apparent change in overall power fade mechanism going from 3% to 6% {Delta}SOC. Here, the power of time changes to a value less than 0.5, indicating that the power fade mechanism is more complex than layer growth. The Gen 2 calendar- and cycle-life experiments show the effect of cell chemistry on kinetics. The calendar-life resistance and power fade follow either linear or linear plus (time){sup 1/2} kinetics, depending on temperature. Temperature dependence for the kinetic law was also found in the …
Date: February 20, 2002
Creator: Bloom, I.; Jones, S. A.; Battaglia, V. S.; Polzin, E. G.; Henriksen, G. L.; Motloch, C. G. et al.
Object Type: Article
System: The UNT Digital Library
Modeling of Laser-Induced Metal Combustion (open access)

Modeling of Laser-Induced Metal Combustion

Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.
Date: February 20, 2008
Creator: Boley, C D & Rubenchik, A M
Object Type: Article
System: The UNT Digital Library
The differentiation history of the terrestrial planets as recorded on the moon (open access)

The differentiation history of the terrestrial planets as recorded on the moon

The outline for this report is: (1) Factors Leading to Lunar Magma Ocean Model for Planetary Differentiation (2) Rationale for Magma Oceans on Other Planets Means for early efficient differentiation (Works on Moon why not here?) (3) Some Inconsistencies between the Lunar Magma Ocean Model and Observations. The conclusions are: (1) Differentiation via solidification of a magma ocean is derived from geologic observations of the Moon (2) Although geologic observations on other bodies are often consistent with differentiation via magma ocean solidification, it is not generally required. (3) There are some fundamental inconsistencies between observed lunar data and the model, that will require this model to be modified (4) Nevertheless, the Moon is the only location we know of to study magma ocean process in detail.
Date: February 20, 2007
Creator: Borg, L
Object Type: Article
System: The UNT Digital Library
Predicting the Cosmological Constant from the CausalEntropic Principle (open access)

Predicting the Cosmological Constant from the CausalEntropic Principle

We compute the expected value of the cosmological constant in our universe from the Causal Entropic Principle. Since observers must obey the laws of thermodynamics and causality, it asserts that physical parameters are most likely to be found in the range of values for which the total entropy production within a causally connected region is maximized. Despite the absence of more explicit anthropic criteria, the resulting probability distribution turns out to be in excellent agreement with observation. In particular, we find that dust heated by stars dominates the entropy production, demonstrating the remarkable power of this thermodynamic selection criterion. The alternative approach--weighting by the number of ''observers per baryon''--is less well-defined, requires problematic assumptions about the nature of observers, and yet prefers values larger than present experimental bounds.
Date: February 20, 2007
Creator: Bousso, Raphael; Harnik, Roni; Kribs, Graham D. & Perez, Gilad
Object Type: Report
System: The UNT Digital Library
Using an Ersatz Thermosiphon Loop to Model Natural Convection Flows Inside a Shallow Enclosure (open access)

Using an Ersatz Thermosiphon Loop to Model Natural Convection Flows Inside a Shallow Enclosure

Natural convection loops (NCL) can occur when extracting energy from thermal storage with immersed heat exchangers. To assist in heat exchanger design and annual performance simulations of such systems, this paper proposes modeling an NCL with a comparatively simple ''ersatz'' thermosiphon loop (ETL). In an actual thermosiphon loop, fluid in channels or pipes flows in a closed loop, driven by a net buoyancy head which is equal to the total pressure drop. In the proposed approach, ersatz flow channels corresponding to the actual NCL flow are first defined, based upon experiment, numerical solution, or other information. The heat transfer and friction coefficients in the simplified ETL model must then be adjusted to fit these known data. The test case analyzed here is a horizontal shallow enclosure with temperature boundary conditions at both ends. A numerical solution is used to calibrate the ETL, and an analytical solution is used to extrapolate to other conditions for testing the ETL mo del predictions. It is shown that over two orders of magnitude variation in heat transfer, the calibrated ETL model predicts the heat transfer to 8% RMSD.
Date: February 20, 2001
Creator: Burch, J.D. & Gawlik, K.M.
Object Type: Article
System: The UNT Digital Library
Efficient Web Change Monitoring with Page Digest (open access)

Efficient Web Change Monitoring with Page Digest

The Internet and the World Wide Web have enabled a publishing explosion of useful online information, which has produced the unfortunate side effect of information overload: it is increasingly difficult for individuals to keep abreast of fresh information. In this paper we describe an approach for building a system for efficiently monitoring changes to Web documents. This paper has three main contributions. First, we present a coherent framework that captures different characteristics of Web documents. The system uses the Page Digest encoding to provide a comprehensive monitoring system for content, structure, and other interesting properties of Web documents. Second, the Page Digest encoding enables improved performance for individual page monitors through mechanisms such as short-circuit evaluation, linear time algorithms for document and structure similarity, and data size reduction. Finally, we develop a collection of sentinel grouping techniques based on the Page Digest encoding to reduce redundant processing in large-scale monitoring systems by grouping similar monitoring requests together. We examine how effective these techniques are over a wide range of parameters and have seen an order of magnitude speed up over existing Web-based information monitoring systems.
Date: February 20, 2004
Creator: Buttler, David J.; Rocco, Daniel & Liu, Ling
Object Type: Article
System: The UNT Digital Library
2005 Electrochemistry Gordon Conference (open access)

2005 Electrochemistry Gordon Conference

This report is on Electrochemistry for Gordon Conference
Date: February 20, 2005
Creator: Buttry, Daniel
Object Type: Article
System: The UNT Digital Library
Determination of Importance Evaluation for Exploratory Studies Facility (ESF) Subsurface Testing Activities (open access)

Determination of Importance Evaluation for Exploratory Studies Facility (ESF) Subsurface Testing Activities

This Determination of Importance Evaluation (DIE) applies to the Subsurface Exploratory Studies Facility (ESF), encompassing the Topopah Spring (TS) Loop from Station 0+00 meters (m) at the North Portal to breakthrough at the South Portal (approximately 78+77 m), and ancillary test and operation support areas including the Enhanced Characterization of the Repository Block (ECRB) Cross Drift. This evaluation applies specifically to site characterization testing activities ongoing and planned in the Subsurface ESF. ESF site characterization activities are being performed to obtain the information necessary to determine whether the Yucca Mountain Site is suitable as a geologic repository for spent nuclear fuel and high-level radioactive waste. A more detailed description of these testing activities is provided in Section 6 of this DIE. Generally, the construction and operation of excavations associated with these testing activities are evaluated in the DIE for the Subsurface ESF (CRWMS M&O 1999a) and the DIE for the ESF ECRB Cross Drift (CRWMS M&O 2000a). The scope of this DIE also entails the proposed Unsaturated Zone (UZ) Transport Test at Busted Butte. Although, not a part of the TS Loop or ECRB Cross Drift, the associated testing activities are Subsurface testing activities. Busted Butte is located to the …
Date: February 20, 2001
Creator: Byrne, C.J.
Object Type: Report
System: The UNT Digital Library
Campaign Finance Bills Passed in the 107th Congress: Comparison of S. 27 (McCain-Feingold), H.R. 2356 (Shays-Meehan), and Current Law (open access)

Campaign Finance Bills Passed in the 107th Congress: Comparison of S. 27 (McCain-Feingold), H.R. 2356 (Shays-Meehan), and Current Law

This report summarizes and compares the two campaign finance reforms bills that have passed the House and Senate in the 107th congress and current law cases.
Date: February 20, 2002
Creator: Cantor, Joseph E. & Whitaker, L. Paige
Object Type: Report
System: The UNT Digital Library