States

New Security Results on Encrypted Key Exchange (open access)

New Security Results on Encrypted Key Exchange

Schemes for encrypted key exchange are designed to provide two entities communicating over a public network, and sharing a (short) password only, with a session key to be used to achieve data integrity and/or message confidentiality. An example of a very efficient and ''elegant'' scheme for encrypted key exchange considered for standardization by the IEEE P1363 Standard working group is AuthA. This scheme was conjectured secure when the symmetric-encryption primitive is instantiated via either a cipher that closely behaves like an ''ideal cipher,'' or a mask generation function that is the product of the message with a hash of the password. While the security of this scheme in the former case has been recently proven, the latter case was still an open problem. For the first time we prove in this paper that this scheme is secure under the assumptions that the hash function closely behaves like a random oracle and that the computational Diffie-Hellman problem is difficult. Furthermore, since Denial-of-Service (DoS) attacks have become a common threat we enhance AuthA with a mechanism to protect against them.
Date: December 15, 2003
Creator: Bresson, Emmanuel; Chevassut, Olivier & Pointcheval, David
System: The UNT Digital Library
On the hydrogen emission from the type Ia supernova 2002ic (open access)

On the hydrogen emission from the type Ia supernova 2002ic

The discovery of SN 2002ic by the Supernova Factory and the subsequent spectroscopic studies have led to the surprising finding that SN 2002ic is a type Ia supernova with strong ejecta-circumstellar interaction. Here we show that nearly 1 year after the explosion the supernova has become fainter overall, but the H-alpha emission has brightened and broadened dramatically compared to earlier observations. We have obtained spectropolarimetry data which show that the hydrogen-rich matter is highly aspherically distributed. These observations suggest that the supernova exploded inside a dense, clumpy, disk-like circumstellar environment.
Date: December 10, 2003
Creator: Wang, Lifan; Baade, Dietrich; Hoflich, Peter; Wheeler, J. Craig; Kawabata, Koji & Nomoto, Ken'ichi
System: The UNT Digital Library
Applications of photoemission electron microscopy (PEEM) in magnetism research (open access)

Applications of photoemission electron microscopy (PEEM) in magnetism research

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Date: December 12, 2003
Creator: Scholl, Andreas
System: The UNT Digital Library
Diffractive physics results at CDF (open access)

Diffractive physics results at CDF

Forward detectors are described together with the first physics results from Run II. Using new data and dedicated diffractive triggers, a measurement of single diffractive dijet production rate, with particular focus on the diffractive structure function of the antiproton, is discussed. Upper limits on the exclusive dijet and {chi}{sub c}{sup 0} production cross sections are also presented.
Date: December 18, 2003
Creator: Gallinaro, Michele
System: The UNT Digital Library
NuTeV cross-section and structure function measurements (open access)

NuTeV cross-section and structure function measurements

The NuTeV experiment has obtained a unique high statistics sample of neutrino and antineutrino interactions using its high-energy sign-selected beam. Charged-current {nu} and {bar {nu}} differential cross sections are extracted. Neutrino-Iron structure functions, F{sub 2}(x, Q{sup 2}) and xF{sub 3}(x, Q{sup 2}), are determined by fitting the y-dependence of the differential cross sections. NuTeV has precise understanding of its hadron and muon energy scales, which improves the systematic precision of this measurement.
Date: December 10, 2003
Creator: al., Donna Naples et
System: The UNT Digital Library
Rare charm and B decays at CDF (open access)

Rare charm and B decays at CDF

We present results on rare charm and B decays using 65pb{sup -1} of data taken with the CDF detector in Run II. Three results are discussed, a measurement of the relative branching ratios {Lambda}(D{sup 0} {yields} K{sup +}K{sup -})/{Lambda}(D{sup 0} {yields} K{pi}) and {Lambda}(D{sup 0} {yields} {pi}{sup +}{pi}{sup -})/{Lambda}(D{sup 0} {yields} K{pi}) and the direct CP-violating decay rate asymmetry, and a limit on the branching ratio of the FCNC decay D{sup 0} {yields} {mu}{sup +}{mu}{sup -}. We also discuss the prospects for the search for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays.
Date: December 15, 2003
Creator: Thom, Julia
System: The UNT Digital Library
Cold asymmetrical fermion superfluids (open access)

Cold asymmetrical fermion superfluids

The recent experimental advances in cold atomic traps have induced a great amount of interest in fields from condensed matter to particle physics, including approaches and prospects from the theoretical point of view. In this work we investigate the general properties and the ground state of an asymmetrical dilute gas of cold fermionic atoms, formed by two particle species having different densities. We have show in a recent paper, that a mixed phase composed of normal and superfluid components is the energetically favored ground state of such a cold fermionic system. Here we extend the analysis and verify that in fact, the mixed phase is the preferred ground state of an asymmetrical superfluid in various situations. We predict that the mixed phase can serve as a way of detecting superfluidity and estimating the magnitude of the gap parameter in asymmetrical fermionic systems.
Date: December 19, 2003
Creator: Caldas, Heron
System: The UNT Digital Library
Effect of Hydroxamate Siderophores on Fe Release and Pb(II) Adsorption by Goethite (open access)

Effect of Hydroxamate Siderophores on Fe Release and Pb(II) Adsorption by Goethite

OAK-B135 Results of laboratory experiments are presented on the dissolution behavior of the mineral, goethite, in the presence of hydroxamate siderophores. Data also are presented on the removal of lead adsorbed on goethite by siderophores.
Date: December 17, 2003
Creator: Sposito, G.
System: The UNT Digital Library
Collider and detector protection at beam accidents (open access)

Collider and detector protection at beam accidents

Dealing with beam loss due to abort kicker prefire is considered for hadron colliders. The prefires occurred at Tevatron (Fermilab) during Run I and Run II are analyzed and a protection system implemented is described. The effect of accidental beam loss in the Large Hadron Collider (LHC) at CERN on machine and detector components is studied via realistic Monte Carlo calculations. The simulations show that beam loss at an unsynchronized beam abort would result in severe heating of conventional and superconducting magnets and possible damage to the collider detector elements. A proposed set of collimators would reduce energy deposition effects to acceptable levels. Special attention is paid to reducing peak temperature rise within the septum magnet and minimizing quench region length downstream of the LHC beam abort straight section.
Date: December 10, 2003
Creator: Rakhno, I. L.; Mokhov, N. V. & Drozhdin, A. I.
System: The UNT Digital Library
Understanding Biodiesel Fuel Quality and Performances (open access)

Understanding Biodiesel Fuel Quality and Performances

The purpose of this paper is to provide the reader with sufficient information to understand Biodiesel fuel quality and the effect various quality parameters have on diesel equipment performance. Biodiesel is produced from vegetable oils, recycled cooking greases and animal fat. The American Society of Testing Material test methods are used as a basis for drawing comparisons between regular diesel fuel and Biodiesel. Failure to control the processes for manufacturing, blending and storage of Biodiesel can lead to performance problems in all types of diesel fueled equipment.
Date: December 12, 2003
Creator: Weiksner, J. M., Sr.; Crump, Stephen L. & White, Thomas L.
System: The UNT Digital Library
The BTeV trigger: Recent developments (open access)

The BTeV trigger: Recent developments

BTeV is a collider experiment at the Fermilab Tevatron dedicated to precision measurements of CP violation, mixing and rare decays of beauty and charm hadrons. The detector is a forward spectrometer with a pixel vertex detector inside a dipole magnet. A unique feature of BTeV is the trigger, which reconstructs tracks and vertices in every beam crossing. They present here an overview of the BTeV trigger and a description of recent improvements in trigger timing.
Date: December 1, 2003
Creator: Kasper, Penelope
System: The UNT Digital Library
Spectroscopic Properties and Potential Energy Curves of Low-lying electronic States of RuC (open access)

Spectroscopic Properties and Potential Energy Curves of Low-lying electronic States of RuC

The RuC molecule has been a challenging species due to the open-shell nature of Ru resulting in a large number of low-lying electronic states. We have carried out state-of-the-art calculations using the complete active space multi-configuration self-consistent field (CASSCF) followed by multireference configuration interaction (MRCI) methods that included up 18 million configurations, in conjunction with relativistic effects. We have computed 29 low-lying electronic states of RuC with different spin multiplicities and spatial symmetries with energy separations less than 38 000 cm{sup -1}. We find two very closely low-lying electronic states for RuC, viz., {sup 1}{Sigma}{sup +} and {sup 3}{Delta} with the {sup 1}{Sigma}{sup +} being stabilized at higher levels of theory. Our computed spectroscopic constants and dipole moments are in good agreement with experiment although we have reported more electronic states than those that have been observed experimentally. Our computations reveal a strongly bound X{sup 1}{Sigma}{sup +} state with a large dipole moment and an energetically close {sup 3}{Delta} state with a smaller dipole moment. Overall our computed spectroscopic constants of the excited states with energy separations less than 18000 cm{sup -1} agree quite well with those of the corresponding observed states.
Date: December 22, 2003
Creator: Balasubramanian, K & Guo, R
System: The UNT Digital Library
The Effect of Habitat Inhomogeneities and Fragmentation on Population Density and Time to Extinction (open access)

The Effect of Habitat Inhomogeneities and Fragmentation on Population Density and Time to Extinction

We present a study, based on simulations with SERDYCA, a spatially-explicit individual based model of rodent dynamics, on the connection between population persistence and the presence of inhomogeneities in the habitat. We are specifically interested on the effect that inhomogeneities that do not fragment the environment, have on population persistence. Our results suggest that a certain percentage of inhomogeneities can increase the average time to extinction of the population. Inhomogeneities decrease the population density and can increase the ratio of juveniles in the population thus providing a better chance for the population to restore itself after a severe period with critically low population density. We call this the ''inhomogeneity localization effect''.
Date: December 22, 2003
Creator: Kostova, Tanya & Carlsen, Tina
System: The UNT Digital Library
Deployment, Commissioning and Operation of Plasma Electrode Pockels Cells in the National Ignition Facility (open access)

Deployment, Commissioning and Operation of Plasma Electrode Pockels Cells in the National Ignition Facility

Large aperture Plasma Electrode Pockels Cells (PEPCs) are an enabling technology in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. The Pockels cells allow the NIF laser to take advantage of multipass main amplifier architecture, thus reducing costs and physical size of the facility. Each Pockels cell comprises four 40-cm x 40-cm apertures arranged in a 4 x 1 array. The combination of the Pockels cell and a thin-film polarizer, also configured in a 4 x 1 array, forms an optical switch that is key to achieving the required multi-pass operation. The operation of the PEPC is a follows: Before the arrival of the laser pulse, optically transparent, low-density helium plasmas are initiated to serve as electrodes for the KDP crystals mounted in the Pockels cell. During beam propagation through the main laser cavity a longitudinal electric field is impressed on the electro-optic crystals. The polarization of the propagating beams is rotated by 90{sup o} on each of two passes, thereby allowing the beam to be trapped in the main laser amplifier cavity for a total of four passes before being switched out into the cavity spatial filter. The physics aspects of the PEPC are well documented. …
Date: December 1, 2003
Creator: Arnold, P. A.; Ollis, C. W.; Hinz, A.; Robb, C.; Primdahl, K. A.; Watson, J. J. et al.
System: The UNT Digital Library
Selection of Batteries and Fuel Cells for Yucca Mountain Robots (open access)

Selection of Batteries and Fuel Cells for Yucca Mountain Robots

The Performance Confirmation program of the Yucca Mountain Repository Development Project needs to employ remotely operated robots to work inside the emplacement drifts which will have an environment unsuitable for humans (radiation environment of up to 200 rad/hour (mostly gamma rays, some neutrons)) and maximum temperatures of 180 C. The robots will be required to operate inside the drifts for up to 8 hours per mission. Based on available functional requirements, we have developed the following specifications for the power needed by the robots:
Date: December 8, 2003
Creator: Upadhye, R S
System: The UNT Digital Library
Simulated (n,f) cross section of isomeric 235m-U (open access)

Simulated (n,f) cross section of isomeric 235m-U

The neutron-induced fission cross section on the {sup 235}U, T{sub 1/2} {approx} 26 min isomer has been deduced for incident neutron energies in the range E{sub n}=0.1-2.5 MeV, using the surrogate-reaction technique. In this technique, {sup 236}U fission probabilities measured in the {sup 234}U(t, pf) reaction have been converted into {sup 235}U(n,f) and {sup 235m}U(n,f) cross sections, using reaction theory to compensate for the differences in angular-momentum and parity distributions in the fissioning systems, transferred by the (t,p) and neutron-induced reactions. Based on the comparison between the {sup 235}U(n,f) cross section extracted in this work and independent experimental data, the deduced {sup 235m}U(n,f) cross section is believed to be reliable to 20% below E{sub n} {approx} 0.5 MeV and 10% at higher energies. The surrogate-reaction technique, its validation in the case of the {sup 235}U(n,f) cross section, and the deduced {sup 235m}U(n,f) cross section are discussed. Validation of this method allows (n,f) cross sections for many short-lived nuclei, as well as isomeric nuclei, to be extracted from measured fission probabilities.
Date: December 18, 2003
Creator: Becker, J; Britt, H & Younes, W
System: The UNT Digital Library
Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow (open access)

Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow

The ignition temperature of nitrogen-diluted dimethyl ether (DME) by heated air in counterflow was experimentally determined for DME concentration from 5.9 to 30%, system pressure from 1.5 to 3.0 atmospheres, and pressure-weighted strain rate from 110 to 170/s. These experimental data were compared with two mechanisms that were respectively available in 1998 and 2003, with the latter being a substantially updated version of the former. The comparison showed that while the 1998-mechanism uniformly over-predicted the ignition temperature, the 2003-mechanism yielded surprisingly close agreement for all experimental data. Sensitivity analysis for the near-ignition state based on both mechanisms identified the deficiencies of the 1998-mechanism, particularly the specifics of the low-temperature cool flame chemistry in effecting ignition at higher temperatures, as the fuel stream is being progressively heated from its cold boundary to the high-temperature ignition region around the hot-stream boundary. The 2003-mechanism, consisting of 79 species and 398 elementary reactions, was then systematically simplified by using the directed relation graph method to a skeletal mechanism of 49 species and 251 elementary reactions, which in turn was further simplified by using computational singular perturbation method and quasi-steady-state species assumption to a reduced mechanism consisting of 33 species and 28 lumped reactions. It …
Date: December 19, 2003
Creator: Zheng, X L; Lu, T F; Law, C K & Westbrook, C K
System: The UNT Digital Library
The MACHO Project Large Magellanic Cloud Variable Star Inventory. XIII. Fourier Parameters for the First Overtone RR Lyrae Variables and the LMC Distance (open access)

The MACHO Project Large Magellanic Cloud Variable Star Inventory. XIII. Fourier Parameters for the First Overtone RR Lyrae Variables and the LMC Distance

Shapes of RR Lyrae light curves can be described in terms of Fourier coefficients which past research has linked with physical characteristics such as luminosity, mass and temperature. Fourier coefficients have been derived for the V and R light curves of 785 overtone RR Lyrae variables in 16 MACHO fields near the bar of the LMC. In general, the Fourier phase differences {phi}{sub 21}, {phi}{sub 31} and {phi}{sub 41} increase and the amplitude ratio R{sub 21} decreases with increasing period. The coefficients for both the V and R magnitudes follow these patterns, but the phase differences for the R curves are on average slightly greater, and their amplitudes are about 20% smaller, than the ones for the V curves. The {phi}{sub 31} and R{sub 21} coefficients have been compared with those of the first overtone RR Lyrae variables in the Galactic globular clusters NGC 6441, M107, M5, M3, M2, {omega} Centauri and M68. The results indicate that many of the LMC variables have properties similar to the ones in M2, M3, M5 and the Oosterhoff type I variables in {omega} Cen, but they are different from the Oosterhoff type II variables in {omega} Cen. Equations derived from hydrodynamic pulsation models …
Date: December 31, 2003
Creator: Alcock, C.; Alves, D.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C. et al.
System: The UNT Digital Library
NIF Capsule Sensitivity to Drive Asymmetry (open access)

NIF Capsule Sensitivity to Drive Asymmetry

We examine 300 eV ICF capsules with ablators of Ge-doped CH, and consider the 2-D parameter space of ablator thickness and DT-ice thickness. At each point in this parameter space, we optimize the drive for a low entropy implosion. At five points in this parameter space, we run 2-D sensitivity studies with radiation drive asymmetries with both constant and time-varying Legendre coefficient P{sub 2}, P{sub 4}, P{sub 6}, and P{sub 8} to determine how much asymmetry the capsule can tolerate before the yield degrades substantially. We find that the thinner capsules with higher implosion velocities are more tolerant of drive asymmetries.
Date: December 17, 2003
Creator: Haan, S; Suter, L; Pollaine, S; Herrmann, M; Amendt, P & Jones, O
System: The UNT Digital Library
Monitoring Permeable Reactive Barriers using Electrical Resistance Tomography (open access)

Monitoring Permeable Reactive Barriers using Electrical Resistance Tomography

An electrical resistivity tomography (ERT) method is being evaluated as a measurement tool to determine the integrity of permeable reactive barriers (PRBs) during and after construction of the barrier and as a monitoring tool to determine the long-term operational health of the barrier. The method is novel because it inserts the electrodes directly into the barrier itself. Numerical modeling calculations indicate that the ERT method can detect flaws (voids) in the barrier as small as 0.11 m{sup 2} (0.33 m x 0.33 m) when the aspect ratio of the electrodes are 2:1. Laboratory measurements indicate that the change in resistance over time of the iron-filling mixture used to create the PRB is sufficient for ERT to monitor the long-term health of the barrier. The use of this ERT method allows for the cost-effective installation of the barrier, especially when the vadose zone is large, because borehole installation methods, rather than trenching methods, can be used.
Date: December 8, 2003
Creator: Ramirez, A.; Bratton, W.; Maresca, J.; Daily, W. & Dickerson, W.
System: The UNT Digital Library
Multinomial Combinatorial Group Representations of the Octahedral and Cubic Symmetries (open access)

Multinomial Combinatorial Group Representations of the Octahedral and Cubic Symmetries

We consider the full multinomial combinatorics of all irreducible representations of the octahedral (cubic) symmetry as a function of partitions for vertex, face and edge colorings. Full combinatorial tables for all irreducible representations and all multinomial partitions are constructed. These enumerations constitute multinomial expansions of character-based cycle index polynomials, and grow in combinatorial complexity as a function of edge or vertex coloring partitions.
Date: December 22, 2003
Creator: Balasubramanian, K
System: The UNT Digital Library
The Solid-State Heat-Capacity Laser (open access)

The Solid-State Heat-Capacity Laser

Heat-capacity operation of a laser is a novel method by which high average powers can be generated. In this paper, we present the principles behind heat-capacity operation, in addition to describing the results of recent experiments.
Date: December 8, 2003
Creator: Rotter, M D; Dane, C B; Gonzales, S A; Merrill, R D; Mitchell, S C; Parks, C W et al.
System: The UNT Digital Library
Isochoric Heating Into the Warm Dense Matter Regime by Laser-Solid Produced K(Alpha) X-Rays (open access)

Isochoric Heating Into the Warm Dense Matter Regime by Laser-Solid Produced K(Alpha) X-Rays

The study of matter at near solid density and at temperatures of 1-10 eV is a great challenge to both experimentalists and theorists, because such matter exhibits internal energy density which is very high but insufficient to overpower the inter-atomic potentials. This form of matter, intermediate to condensed matter and plasmas, exists in many astrophysical systems. In this paper, we describe an experimental program to study solid-density matter heated to temperatures near 1 eV per atom with ultrafast pulses of x-rays. An intense, ultra-short laser pulse incident upon a thin foil produces a burst of K-{alpha} x-rays, which are used to flash heat an adjacent bulk sample. Optical interferometric probing of the sample with sub-ps time resolution allows us to measure its expansion into vacuum upon heating. K-{alpha} source target properties are optimized for irradiation of the adjacent sample. Initial results on K-{alpha} yields and heating of Al foils will be discussed.
Date: December 13, 2003
Creator: Dyer, G; Ditmire, T; Shepherd, R; Kuba, J; Price, D; Wootton, A et al.
System: The UNT Digital Library
Deliquescence of NaCl-NaNO3 and KNO3-NaNO3 Salt Mixtures at 90C (open access)

Deliquescence of NaCl-NaNO3 and KNO3-NaNO3 Salt Mixtures at 90C

We conducted reversed deliquescence experiments in saturated NaCl-NaNO3-H2O and KNO{sub 3}-NaNO{sub 3}-H{sub 2}O systems at 90 C to determine relative humidity and solution composition. NaCl, NaNO{sub 3}, and KNO{sub 3} represent members of dust salt assemblages that are likely to deliquesce and form concentrated brines on high-level radioactive waste package surfaces in a repository environment at Yucca Mountain, NV, USA. Model predictions agree with experimental results for the NaCl-NaNO{sub 3}-H{sub 2}O system, but underestimate relative humidity by as much as 8% and solution composition by as much as 50% in the KNO{sub 3}-NaNO{sub 3}-H{sub 2}O system.
Date: December 29, 2003
Creator: Carroll, S; Craig, L & Wolery, T
System: The UNT Digital Library