Resource Type

Month

High-Performance Corrosion-Resistant Iron-Based Amorphous Metals: The Effects of Composition, Structure and Environment on Corrosion Resistance (open access)

High-Performance Corrosion-Resistant Iron-Based Amorphous Metals: The Effects of Composition, Structure and Environment on Corrosion Resistance

New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative thermal phase stability, microstructure, mechanical properties, damage tolerance, and corrosion resistance. Some alloy additions are known to promote glass formation and to lower the critical cooling rate [F. Guo, S. J. Poon, Applied Physics Letters, 83 (13) 2575-2577, 2003]. Other elements are known to enhance the corrosion resistance of conventional stainless steels and nickel-based alloys [A. I. Asphahani, Materials Performance, Vol. 19, No. 12, pp. 33-43, 1980] and have been found to provide similar benefits to iron-based amorphous metals. Many of these materials can be cast as relatively thick ingots, or applied as coatings with advanced thermal spray technology. A wide variety of thermal spray processes have been developed by industry, and can be used to apply these new materials as coatings. Any of these can be used for the deposition of the formulations discussed here, with varying degrees of residual porosity and crystalline structure. Thick protective coatings have now been made that are fully dense and completely amorphous in the as-sprayed condition. An overview of the High-Performance Corrosion Resistant Materials (HPCRM) Project will be given, with particular …
Date: April 11, 2006
Creator: Farmer, J; Choi, J S; Haslam, J; Lian, T; Day, S; Yang, N et al.
System: The UNT Digital Library
Dark Energy in the Dark Ages (open access)

Dark Energy in the Dark Ages

Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or"reasonable'" canonical scalar fields. Such dark energy can be constrained tightly through investigation of the growth of structure, with limits of<~;;2percent of total energy density at z>> 1 for many models. Intermediate dark energy can have effects distinct from its energy density; the dark ages acceleration can be constrained to last less than 5percent of a Hubble e-fold time, exacerbating the coincidence problem. Both the total linear growth, or equivalently sigma 8, and the shape and evolution of the nonlinear mass power spectrum for z<2 (using the Linder-White nonlinear mapping prescription) provide important windows. Probes of growth, such as weak gravitational lensing, can interact with supernovae and CMB distance measurements to scan dark energy behavior over the entire range z=0-1100.
Date: April 11, 2006
Creator: Linder, Eric V.
System: The UNT Digital Library
A Novel Mechanical Method to Measure Shear Strength in Specimens Under Pressure (open access)

A Novel Mechanical Method to Measure Shear Strength in Specimens Under Pressure

A new experimental apparatus has been developed for performing shear tests on specimens held under moderately high hydrostatic pressures (on the order of 4 GPa). This testing procedure experimentally determines the pressure-dependent shear strength of thin foil specimens. The experiments provide calibration data for models of materials subjected to extreme pressures such as the Steinberg-Guinan hardening model and can assist in model validation for discrete dislocation dynamics simulations, among others. This paper reports the development of the experimental procedures and the results of initial experiments on thin foils of polycrystalline Ta performed under hydrostatic pressures ranging from 1 to 4 GPa. Both yielding and hardening behavior of Ta are observed to be sensitive to the imposed pressure.
Date: April 11, 2006
Creator: Escobedo, J. P.; Field, D.; Lassila, D. & Leblanc, M.
System: The UNT Digital Library
Origin and properties of GEMS (open access)

Origin and properties of GEMS

GEMS are to the outer solar system what chondrules are to the inner solar system. Ten years after it was first proposed that GEMS are the long-sought interstellar amorphous silicates, ion microprobe measurements have confirmed that some of them are indeed interstellar amorphous silicates. The new challenges are to obtain even higher precision isotope measurements from these submicrometer-sized objects and to clarify how and where they originally formed. Individual GEMS exhibit a strikingly narrow (0.1-0.5 {micro}m diameter) size distribution and they are systematically depleted from solar abundances in S/Si, Mg/Si, Ca/Si and Fe/Si, implying that they formed by a common mechanism. Mineralogical and petrographic evidence suggest that irradiation processing may be that mechanism. Recent nanometer-scale compositional mapping using new-generation transmission electron microscopes reveals that truly pristine GEMS may be relatively rare and new metrics need to be developed to distinguish the primordial properties of GEMS from more recent secondary alteration effects.
Date: April 11, 2006
Creator: Dai, Z R & Bradley, J P
System: The UNT Digital Library
Measurement of CP Asymmetry in B0 ---> F0 K0(S), B0 ---> Phi K0 And B0 ---> K+ K- K0(S) Decays (open access)

Measurement of CP Asymmetry in B0 ---> F0 K0(S), B0 ---> Phi K0 And B0 ---> K+ K- K0(S) Decays

The authors present results on time-dependent CP asymmetries in f{sub 0}(980)({yields} {pi}{sup +}{pi}{sup -})K{sub S}{sup 0} and B{sup 0} {yields} K{sup +}K{sup -}K{sup 0}. The measurements use a data sample consisting of approximately 209(f{sub 0}(980)({yields} {pi}{sup +}{pi}{sup -})K{sub S}{sup 0}) and 227(B{sup 0} {yields} K{sup +}K{sup -}K{sup 0}) million B-meson pairs recorded at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II B-meson Factory at SLAC.
Date: April 11, 2006
Creator: Kutter, Paul E.
System: The UNT Digital Library
Hadronic Tau Decay at BaBar (open access)

Hadronic Tau Decay at BaBar

Recent results on hadronic decays of tau from BaBar are reviewed. The branching fraction of {tau}{sup -} {yields} 3h{sup -} 2h{sup +}{nu}{sub {tau}} is measured to be (8.56 {+-} 0.05{sub stat} {+-} 0.42{sub sys}) x 10{sup -4}. The underlaying substructure of this decay exposes strong contribution from {rho} resonance. The decay {tau}{sup -} {yields} f{sub 1}(1285){pi}{sup -} {nu}{sub {tau}} with f{sub 1}(1285) {yields} 2{pi}{sup -}2{pi}{sup +} is observed and the corresponding branching fraction is measured to be (3.9 {+-} 0.7{sub stat} {+-} 0.5{sub sys}) x 10{sup -4}. The search for {tau}{sup -} {yields} 4{pi}{sup -}3{pi}{sup +}({pi}{sup 0}){nu}{sub {tau}} decay was performed and without evidence of the signal the upper limit of B({tau}{sup -} {yields} 4{pi}{sup -}3{pi}{sup +}({pi}{sup 0}){nu}{sub {tau}}) is estimated to be 3.0 x 10{sup -7} at 90% confidence limit. The upper limits on branching fractions for the exclusive decays {tau}{sup -} {yields} 4{pi}{sup -}3{pi}{sup +}{nu}{sub {tau}} and {tau}{sup -} {yields} 4{pi}{sup -}3{pi}{sup +}{pi}{sup 0}{nu}{sub {tau}} are found to be 4.3 x 10{sup -7} and 2.5 x 10{sup -7} at 90% confidence limit, respectively.
Date: April 11, 2006
Creator: Igonkina, O. & U., /Oregon
System: The UNT Digital Library
Methodology for Selection of Proper Material Form for Specification of Inhalation Dose Conversion Factors at Savannah River Site. (open access)

Methodology for Selection of Proper Material Form for Specification of Inhalation Dose Conversion Factors at Savannah River Site.

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Date: April 11, 2006
Creator: Thoman, D. C.; East, J. M. & O'Kula, Kevin R.
System: The UNT Digital Library